U.S. patent application number 15/346190 was filed with the patent office on 2017-02-23 for composite material, light-emitting element, light-emitting device, electronic device, and lighting device.
This patent application is currently assigned to Semiconductor Energy Laboratory Co., Ltd.. The applicant listed for this patent is Semiconductor Energy Laboratory Co., Ltd.. Invention is credited to Hiromi Nowatari, Harue OSAKA, Satoshi SEO, Takako TAKASU.
Application Number | 20170054088 15/346190 |
Document ID | / |
Family ID | 45889032 |
Filed Date | 2017-02-23 |
United States Patent
Application |
20170054088 |
Kind Code |
A1 |
Nowatari; Hiromi ; et
al. |
February 23, 2017 |
Composite Material, Light-Emitting Element, Light-Emitting Device,
Electronic Device, and Lighting Device
Abstract
A composite material including an organic compound and an
inorganic compound and having a high carrier-transport property is
provided. A composite material having a high carrier-injection
property to an organic compound is provided. A composite material
in which light absorption due to charge transfer interaction is
unlikely to occur is provided. A light-emitting element having high
emission efficiency is provided by including the composite
material. A light-emitting element having a low drive voltage is
provided. A light-emitting element having a long lifetime is
provided. A composite material including a heterocyclic compound
having a dibenzothiophene skeleton or a dibenzofuran skeleton and
an inorganic compound exhibiting an electron-accepting property
with respect to the heterocyclic compound is provided.
Inventors: |
Nowatari; Hiromi; (Atsugi,
JP) ; SEO; Satoshi; (Sagamihara, JP) ; OSAKA;
Harue; (Sagamihara, JP) ; TAKASU; Takako;
(Chigasaki, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Semiconductor Energy Laboratory Co., Ltd. |
Kanagawa-ken |
|
JP |
|
|
Assignee: |
Semiconductor Energy Laboratory
Co., Ltd.
Kanagawa-ken
JP
|
Family ID: |
45889032 |
Appl. No.: |
15/346190 |
Filed: |
November 8, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
13241694 |
Sep 23, 2011 |
9496505 |
|
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15346190 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01L 51/0074 20130101;
C09K 2211/1007 20130101; H05B 33/14 20130101; C09K 2211/1092
20130101; C09K 11/06 20130101; H01L 2251/303 20130101; H01L 51/5048
20130101; H01L 51/0072 20130101; H01L 51/50 20130101; H01L 51/0052
20130101; C09K 2211/1088 20130101; H01L 51/0073 20130101; C09K
2211/1011 20130101 |
International
Class: |
H01L 51/00 20060101
H01L051/00 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 4, 2010 |
JP |
2010-225037 |
May 31, 2011 |
JP |
2011-122827 |
Claims
1. A composite material comprising: a heterocyclic compound
comprising one of a dibenzothiophene skeleton and a dibenzofuran
skeleton; and an inorganic compound exhibiting an
electron-accepting property with respect to the heterocyclic
compound.
Description
TECHNICAL FIELD
[0001] This application is a continuation of copending U.S.
application Ser. No. 13/241,694, filed on Sep. 23, 2011 which is
incorporated herein by reference.
[0002] The present invention relates to a composite material
including an organic compound and an inorganic compound, a
light-emitting element, a light-emitting device, an electronic
device, and a lighting device.
BACKGROUND ART
[0003] In recent years, research and development have been
extensively conducted on light-emitting elements using organic
electroluminescence (EL). In a basic structure of such a
light-emitting element, a layer containing a light-emitting organic
compound is interposed between a pair of electrodes. By applying
voltage to this element, light emission from the light-emitting
organic compound can be obtained.
[0004] Since such a light-emitting element is of
self-light-emitting type, it is considered that the light-emitting
element has advantages over a liquid crystal display in that
visibility of pixels is high, backlight is not required, and so on
and is therefore suitable as flat panel display elements. In
addition, it is also a great advantage that the light-emitting
element can be manufactured as a thin and lightweight element.
Furthermore, very high speed response is also one of the features
of such elements.
[0005] Furthermore, since such light-emitting elements can be
formed in a film form, they make it possible to easily faun a
large-area element. This feature is difficult to obtain with point
light sources typified by incandescent lamps and LEDs or linear
light sources typified by fluorescent lamps. Thus, light-emitting
elements also have great potential as planar light sources
applicable to lighting devices and the like.
[0006] As described above, application of light-emitting elements
using organic EL to light-emitting devices, lighting devices, or
the like is expected. On the other hand, there are many issues
regarding light-emitting elements using organic EL. One of the
issues is a reduction in power consumption. It is important to
reduce a drive voltage for the light-emitting element in order to
reduce power consumption. Further, the emission intensity of the
light-emitting element using organic EL is determined by the amount
of electric current flowing therein. Therefore, in order to reduce
the drive voltage, it is necessary to feed a large amount of
current at low voltage.
[0007] Previously, as a method for reducing drive voltage, an
approach of providing a buffer layer between an electrode and the
layer including a light-emitting organic compound, has been
attempted. For example, it is known that a drive voltage can be
reduced by providing a buffer layer which includes polyaniline
(PANI) doped with camphorsulfonic acid, between indium tin oxide
(ITO) and a light-emitting layer (see Non-Patent Document 1, for
example). It is explained that this is because of the excellent
carrier-injection property of PANI to the light-emitting layer.
Note that in Non-Patent Document 1, PANI that is the buffer layer
is also considered to be a part of the electrode.
[0008] However, as described in Non-Patent Document 1, PANI has a
problem that transmittance becomes poor when a film thickness
becomes thick. Specifically, it is reported that at a film
thickness of about 250 nm, the transmittance is less than 70%. In
other words, since the problem is with the transparency of the
material itself that is used for the buffer layer, light that is
generated within the element cannot be taken out efficiently.
[0009] Also, according to Patent Document 1, an approach of
serially connecting light-emitting elements (called light-emitting
units in Patent Document 1) to improve the luminance per a certain
current density, in other words, current efficiency, has been
attempted. In Patent Document 1, for a connecting portion of
serially connected light-emitting elements, a mixed layer of an
organic compound and a metal oxide (specifically, vanadium oxide
and rhenium oxide) is used, and it is considered that this layer
can inject holes and electrons to light-emitting units.
[0010] However, as apparent by looking at an embodiment, for the
mixed layer of an organic compound and a metal oxide that is
disclosed in Patent Document 1, a high absorption peak is observed
not only in the infrared region but also in the visible light
region (around 500 nm), and a problem in transparency occurs also.
This is due to the effect of an absorption band generated by charge
transfer interaction. Therefore, as expected, light that is
generated within the element cannot be taken out efficiently, and
the light emission efficiency of the element is degraded.
REFERENCES
[0011] [Patent Document 1] Japanese Published Patent Application
No. 2003-272860 [0012] [Non-Patent Document 1] Y. Yang et al.,
Applied Physics Letters, Vol. 64 (10), 1245-1247 (1994)
DISCLOSURE OF INVENTION
[0013] In view of the above description, it is an object of one
embodiment of the present invention to provide a composite material
including an organic compound and an inorganic compound and having
a high carrier-transport property. It is another object to provide
a composite material having a high carrier-injection property to an
organic compound. It is another object to provide a composite
material in which light absorption due to charge transfer
interaction is unlikely to occur.
[0014] It is an object of one embodiment of the present invention
to provide a light-emitting element having high emission efficiency
by application of the above-described composite material to the
light-emitting element. It is another object to provide a
light-emitting element having a low drive voltage. It is another
object to provide a light-emitting element having a long lifetime.
It is another object to provide a light-emitting device including
the light-emitting element, an electronic device including the
light-emitting device, or a lighting device including the
light-emitting device.
[0015] Note that an object of the invention to be disclosed below
is to achieve at least one of the above-described objects.
[0016] One embodiment of the present invention is a composite
material including a heterocyclic compound having a
dibenzothiophene skeleton or a dibenzofuran skeleton and an
inorganic compound exhibiting an electron-accepting property with
respect to the heterocyclic compound.
[0017] Thiophene and furan are .pi.-electron-rich heteroaromatic
rings and therefore each exhibit a hole-transport property. Thus,
the above-described composite material has a high carrier-transport
property.
[0018] The above-described composite material also has a high
carrier-injection property to an organic compound. In the composite
material, light absorption due to charge transfer interaction is
unlikely to occur, and the composite material has a high
visible-light-transmitting property (hereinafter referred to as a
light-transmitting property).
[0019] Another embodiment of the present invention is a composite
material including a heterocyclic compound having a substituent
having 6 to 70 carbon atoms bonded to the 4-position of a
dibenzothiophene skeleton or a dibenzofuran skeleton, and an
inorganic compound exhibiting an electron-accepting property with
respect to the heterocyclic compound.
[0020] It is preferable to use the heterocyclic compound having a
substituent at the 4-position of a dibenzothiophene skeleton or a
dibenzofuran skeleton for a composite material because it is
possible to suppress the occurrence of light absorption based on
charge transfer interaction, and also because it is possible to
stabilize the film quality of the composite material.
[0021] It is preferable that a ring of the substituent in the
above-described composite material be one or a plurality of rings
selected from a benzene ring, a naphthalene ring, a phenanthrene
ring, a triphenylene ring, a fluorene ring, a dibenzothiophene
ring, and a dibenzofuran ring. This makes it possible not only to
suppress the occurrence of light absorption based on charge
transfer interaction but also to control an absorption peak of the
heterocyclic compound itself so as to appear at a shorter
wavelength than the visible light region (380 nm to 760 nm); thus,
a composite material having a particularly high light-transmitting
property can be obtained.
[0022] It is particularly preferable that the ring of the
substituent be one or a plurality of rings selected from a benzene
ring, a fluorene ring, a dibenzothiophene ring, and a dibenzofuran
ring. In this case, light absorption based on charge transfer
interaction with the inorganic compound hardly occurs.
[0023] Another embodiment of the present invention is a composite
material including a heterocyclic compound having a phenyl group
bonded to the 4-position of a dibenzothiophene skeleton or a
dibenzofuran skeleton, in which the phenyl group has one or more
substituents and the phenyl group and the one or more substituents
have a total of 12 to 70 carbon atoms, and an inorganic compound
exhibiting an electron-accepting property with respect to the
heterocyclic compound.
[0024] It is preferable to use a heterocyclic compound having a
phenyl group with small conjugation bonded to the 4-position of the
dibenzothiophene skeleton or the dibenzofuran skeleton for a
composite material because it is possible to suppress the
occurrence of light absorption based on charge transfer
interaction, because it is possible to stabilize the film quality
of the composite material, and also because it is possible to make
conjugation unlikely to extend, which is also effective in terms of
improving a light-transmitting property.
[0025] It is preferable that a ring of the one or more substituents
in the above-described composite material be separately one or a
plurality of rings selected from a benzene ring, a naphthalene
ring, a phenanthrene ring, a triphenylene ring, a fluorene ring, a
dibenzothiophene ring, and a dibenzofuran ring. This makes it
possible not only to suppress the occurrence of light absorption
based on charge transfer interaction but also to control an
absorption peak of the heterocyclic compound itself to appear at a
shorter wavelength than the visible light region; thus, a composite
material having a particularly high light-transmitting property can
be obtained.
[0026] It is particularly preferable that the ring of the one or
more substituents be separately one or a plurality of rings
selected from a benzene ring, a fluorene ring, a dibenzothiophene
ring, and a dibenzofuran ring. In this case, light absorption based
on charge transfer interaction with the inorganic compound hardly
occurs.
[0027] Another embodiment of the present invention is a composite
material including a heterocyclic compound represented by a general
formula (GI) and an inorganic compound exhibiting an
electron-accepting property with respect to the heterocyclic
compound.
##STR00001##
[0028] In the formula, A represents oxygen or sulfur; R.sup.1 to
R.sup.7 separately represent hydrogen, an alkyl group having 1 to 4
carbon atoms, or an aryl group having 6 to 25 carbon atoms in a
ring; R.sup.8 to R.sup.12 separately represent hydrogen, a
substituted or unsubstituted phenyl group, a substituted or
unsubstituted naphthyl group, a substituted substituted or
unsubstituted fluorenyl group, a substituted or unsubstituted
dibenzothiophenyl group, or a substituted or unsubstituted
dibenzofuranyl group. Note that at least one of R.sup.8 to R.sup.12
represents a substituted or unsubstituted phenyl group, a
substituted or unsubstituted naphthyl group, a substituted or
unsubstituted phenanthryl group, a substituted or unsubstituted
triphenylenyl group, a substituted or unsubstituted fluorenyl
group, a substituted or unsubstituted dibenzothiophenyl group, or a
substituted or unsubstituted dibenzofuranyl group.
[0029] It is particularly preferable that R.sup.8 to R.sup.12
separately represent hydrogen, a substituted or unsubstituted
phenyl group, a substituted or unsubstituted fluorenyl group, a
substituted or unsubstituted dibenzothiophenyl group, or a
substituted or unsubstituted dibenzofuranyl group. Note that at
least one of R.sup.8 to R.sup.12 represents a substituted or
unsubstituted phenyl group, a substituted or unsubstituted
fluorenyl group, a substituted or unsubstituted dibenzothiophenyl
group, or a substituted or unsubstituted dibenzofuranyl group.
[0030] Another embodiment of the present invention is a composite
material including a heterocyclic compound having a
dibenzothiophene skeleton or a dibenzofuran skeleton, and a
transition metal oxide.
[0031] The above-described composite material has a high
carrier-transport property. The above-described composite material
also has a high carrier-injection property to an organic compound.
In the composite material, light absorption due to charge transfer
interaction is unlikely to occur, and the composite material has a
high light-transmitting property.
[0032] Another embodiment of the present invention is a composite
material including a heterocyclic compound having a substituent
having 6 to 70 carbon atoms bonded to the 4-position of a
dibenzothiophene skeleton or a dibenzofuran skeleton, and a
transition metal oxide.
[0033] It is preferable to use the heterocyclic compound having a
substituent at the 4-position of a dibenzothiophene skeleton or a
dibenzofuran skeleton for a composite material because it is
possible to suppress the occurrence of light absorption based on
charge transfer interaction, and also because it is possible to
stabilize the film quality of the composite material.
[0034] It is preferable that a ring of the substituent in the
above-described composite material be one or a plurality of rings
selected from a benzene ring, a naphthalene ring, a phenanthrene
ring, a triphenylene ring, a fluorene ring, a dibenzothiophene
ring, and a dibenzofuran ring. This makes it possible not only to
suppress the occurrence of light absorption based on charge
transfer interaction but also to control an absorption peak of the
heterocyclic compound itself to appear at a shorter wavelength than
the visible light region; thus, a composite material having a
particularly high light-transmitting property can be obtained.
[0035] It is particularly preferable that a ring of the substituent
be one or a plurality of rings selected from a benzene ring, a
fluorene ring, a dibenzothiophene ring, and a dibenzofuran ring. In
this case, light absorption based on charge transfer interaction
with the transition metal oxide hardly occurs.
[0036] Another embodiment of the present invention is a composite
material including a heterocyclic compound having a phenyl group
bonded to the 4-position of a dibenzothiophene skeleton or a
dibenzofuran skeleton, in which the phenyl group has one or more
substituents and the phenyl group and the one or more substituents
have a total of 12 to 70 carbon atoms, and a transition metal
oxide.
[0037] It is preferable to use a heterocyclic compound having a
phenyl group with small conjugation bonded to the 4-position of the
dibenzothiophene skeleton or the dibenzofuran skeleton for a
composite material because it is possible to suppress the
occurrence of light absorption based on charge transfer
interaction, because it is possible to stabilize the film quality
of the composite material, and also because it is possible to make
conjugation unlikely to extend, which is also effective in terms of
improving a light-transmitting property.
[0038] It is preferable that a ring of the one or more substituents
in the above-described composite material be separately one or a
plurality of rings selected from a benzene ring, a naphthalene
ring, a phenanthrene ring, a triphenylene ring, a fluorene ring, a
dibenzothiophene ring, and a dibenzofuran ring. This makes it
possible not only to suppress the occurrence of light absorption
based on charge transfer interaction but also to control an
absorption peak of the heterocyclic compound itself to appear at a
shorter wavelength than the visible light region; thus, a composite
material having a particularly high light-transmitting property can
be obtained.
[0039] It is particularly preferable that a ring of the one or more
substituents be separately one or a plurality of rings selected
from a benzene ring, a fluorene ring, a dibenzothiophene ring, and
a dibenzofuran ring. In this case, light absorption based on charge
transfer interaction with the transition metal oxide hardly
occurs.
[0040] Another embodiment of the present invention is a composite
material including a heterocyclic compound represented by a general
formula (G1) and a transition metal oxide.
##STR00002##
[0041] In the formula, A represents oxygen or sulfur; R.sup.1 to
R.sup.7 separately represent hydrogen, an alkyl group having 1 to 4
carbon atoms, or an aryl group having 6 to 25 carbon atoms in a
ring; R.sup.8 to R.sup.12 separately represent hydrogen, a
substituted or or unsubstituted phenanthryl group, a substituted or
unsubstituted triphenylenyl group, a substituted or unsubstituted
fluorenyl group, a substituted or unsubstituted dibenzothiophenyl
group, or a substituted or unsubstituted dibenzofuranyl group. Note
that at least one of R.sup.8 to R.sup.12 represents a substituted
or unsubstituted phenyl group, a substituted or unsubstituted
naphthyl group, a substituted or unsubstituted phenanthryl group, a
substituted or unsubstituted triphenylenyl group, a substituted or
unsubstituted fluorenyl group, a substituted or unsubstituted
dibenzothiophenyl group, or a substituted or unsubstituted
dibenzofuranyl group.
[0042] It is particularly preferable that R.sup.8 to R.sup.12
separately represent hydrogen, a substituted or unsubstituted
phenyl group, a substituted or unsubstituted fluorenyl group, a
substituted or unsubstituted dibenzothiophenyl group, or a
substituted or unsubstituted dibenzofuranyl group. Note that at
least one of R.sup.8 to R.sup.12 represents a substituted or
unsubstituted phenyl group, a substituted or unsubstituted
fluorenyl group, a substituted or unsubstituted dibenzothiophenyl
group, or a substituted or unsubstituted dibenzofuranyl group.
[0043] It is preferable that the transition metal oxide included in
the above-described composite material be one or a plurality of
oxides selected from titanium oxide, vanadium oxide, molybdenum
oxide, tungsten oxide, rhenium oxide, ruthenium oxide, chromium
oxide, zirconium oxide, hafnium oxide, tantalum oxide, and silver
oxide.
[0044] It is preferable that the highest occupied molecular orbital
level (HOMO level) of the heterocyclic compound used for the
above-described composite material, which is measured by
photoelectron spectrometry, be lower than or equal to -5.7 eV.
[0045] Another embodiment of the present invention is a
light-emitting element including a layer containing a
light-emitting substance (hereinafter also referred to as an EL
layer) between a pair of electrodes. The layer including a
light-emitting substance includes a layer including the
above-described composite material.
[0046] In the above-described light-emitting element, it is
preferable that the layer including the composite material be in
contact with one of the pair of electrodes which functions as an
anode. It is also preferable that the layer including the composite
material be in contact with one of the pair of electrodes which
functions as a cathode.
[0047] The above-described light-emitting element may include two
layers including the composite material, and it is preferable that
one of the two layers including the composite material be in
contact with one of the pair of electrodes which functions as an
anode and the other of the two layers be in contact with the other
of the pair of electrodes which functions as a cathode.
[0048] Another embodiment of the present invention is a
light-emitting element including a plurality of layers including a
light-emitting substance between a pair of electrodes, and
including a layer including the above-described composite material
between the plurality of layers including a light-emitting
substance. In other words, the above-described composite material
can be used for an intermediate layer (also referred to as a
charge-generation layer) in an organic EL light-emitting element
including a stack of a plurality of light-emitting units (a tandem
organic EL light-emitting element).
[0049] Another embodiment of the present invention is a
light-emitting device including the above-described light-emitting
element. Another embodiment of the present invention is an
electronic device including the light-emitting device in a display
portion. Another embodiment of the present invention is a lighting
device including the light-emitting element in a light-emitting
portion.
[0050] According to one embodiment of the present invention, it is
possible to provide a composite material including an organic
compound and an inorganic compound and having a high
carrier-transport property. It is also possible to provide a
composite material having a high carrier-injection property to an
organic compound. It is also possible to provide a composite
material in which light absorption due to charge transfer
interaction is unlikely to occur.
[0051] According to one embodiment of the present invention, it is
possible to provide a light-emitting element having high emission
efficiency by application of the above-described composite material
to the light-emitting element. It is also possible to provide a
light-emitting element having a low drive voltage. It is also
possible to provide a light-emitting element having a long
lifetime. It is also possible to provide a light-emitting device
including the light-emitting element, an electronic device
including the light-emitting device, or a lighting device including
the light-emitting device.
BRIEF DESCRIPTION OF DRAWINGS
[0052] FIGS. 1A to 1C illustrate light-emitting elements of one
embodiment of the present invention.
[0053] FIGS. 2A and 2B illustrate light-emitting elements of one
embodiment of the present invention.
[0054] FIGS. 3A and 3B illustrate a light-emitting device of one
embodiment of the present invention.
[0055] FIGS. 4A and 4B illustrate a light-emitting device of one
embodiment of the present invention.
[0056] FIGS. 5A to 5E each illustrate an electronic device of one
embodiment of the present invention.
[0057] FIG. 6 illustrates a lighting device of one embodiment of
the present invention.
[0058] FIGS. 7A and 7B show absorptance of a composite material of
one embodiment of the present invention.
[0059] FIGS. 8A and 8B show absorptance of a composite material of
one embodiment of the present invention.
[0060] FIGS. 9A and 9B show absorptance of a composite material of
one embodiment of the present invention.
[0061] FIGS. 10A and 10B show absorptance of a composite material
of one embodiment of the present invention.
[0062] FIGS. 11A and 11B show absorptance of a composite material
of one embodiment of the present invention.
[0063] FIGS. 12A and 12B show absorptance of a composite material
of one embodiment of the present invention.
[0064] FIGS. 13A and 13B show absorptance of a composite material
of one embodiment of the present invention.
[0065] FIGS. 14A and 14B show absorptance of a composite material
of one embodiment of the present invention.
[0066] FIGS. 15A and 15B show absorptance of a composite material
of one embodiment of the present invention.
[0067] FIGS. 16A and 16B each illustrate a light-emitting element
of an example.
[0068] FIG. 17 shows voltage-luminance characteristics of a
light-emitting element of Example 2.
[0069] FIG. 18 shows luminance-current efficiency characteristics
of a light-emitting element of Example 2.
[0070] FIG. 19 shows results of reliability tests of a
light-emitting element of Example 2.
[0071] FIG. 20 shows voltage-luminance characteristics of a
light-emitting element of Example 3.
[0072] FIG. 21 shows luminance-current efficiency characteristics
of a light-emitting element of Example 3.
[0073] FIG. 22 shows results of reliability tests of a
light-emitting element of Example 3.
[0074] FIG. 23 shows voltage-luminance characteristics of a
light-emitting element of Example 4.
[0075] FIG. 24 shows luminance-current efficiency characteristics
of a light-emitting element of Example 4.
[0076] FIGS. 25A and 25B show absorptance of a composite material
of one embodiment of the present invention.
[0077] FIGS. 26A and 26B show absorptance of a composite material
of one embodiment of the present invention.
[0078] FIGS. 27A and 27B show absorptance of a composite material
of one embodiment of the present invention.
[0079] FIGS. 28A and 28B show absorptance of a composite material
of one embodiment of the present invention.
[0080] FIGS. 29A and 29B show absorptance of a composite material
of one embodiment of the present invention.
[0081] FIG. 30 shows voltage-luminance characteristics of a
light-emitting element of Example 6.
[0082] FIG. 31 shows luminance-current efficiency characteristics
of a light-emitting element of Example 6.
[0083] FIG. 32 shows results of a reliability test of a
light-emitting element of Example 6.
[0084] FIG. 33 shows voltage-luminance characteristics of a
light-emitting element of Example 7.
[0085] FIG. 34 shows luminance-current efficiency characteristics
of a light-emitting element of Example 7.
[0086] FIG. 35 shows voltage-luminance characteristics of a
light-emitting element of Example 8.
[0087] FIG. 36 shows luminance-current efficiency characteristics
of a light-emitting element of Example 8.
[0088] FIG. 37 shows voltage-luminance characteristics of a
light-emitting element of Example 9.
[0089] FIG. 38 shows luminance-current efficiency characteristics
of a light-emitting element of Example 9.
[0090] FIGS. 39A and 39B show absorptances of PCzPA and a composite
material thereof.
[0091] FIGS. 40A and 40B show absorptances of NPB and a composite
material thereof.
[0092] FIG. 41 shows results of ESR measurement of Example 10.
[0093] FIGS. 42A and 42B show results of ESR measurement of Example
10.
BEST MODE FOR CARRYING OUT THE INVENTION
[0094] Embodiments and examples will be described in detail with
reference to the drawings. Note that the present invention is not
limited to the following description and it will be readily
appreciated by those skilled in the art that the modes and details
of the present invention can be modified in various ways without
departing from the spirit and scope thereof. Therefore, the present
invention should not be interpreted as being limited to the
description in the following embodiments and examples. Note that
the same portions or portions having similar functions are commonly
denoted by the same reference numerals in different drawings, and
repetitive description thereof is omitted.
[0095] First, a difference between the background art of the
present invention and the present invention will be briefly
described. As disclosed in Patent Document 1, it is interpreted
that in a composite material including a mixture of an aromatic
amine and an electron-accepting inorganic compound, the
electron-accepting inorganic compound takes electrons from the
aromatic amine, and accordingly, holes and electrons are generated
in the aromatic amine and the inorganic compound, respectively. In
other words, it is interpreted that in such a composite material,
the aromatic amine and the electron-accepting inorganic compound
form a charge-transfer complex. Some composite materials utilizing
such a phenomenon and having excellent carrier-transport and/or
carrier-injection properties have been reported so far.
[0096] However, it is generally known that in such a case, an
absorption band based on charge transfer interaction is generated.
It is said that this absorption band is generated in the deep-red
to near-infrared regions; in fact, in many cases, an absorption
band is also generated in the visible light region. For example, a
composite material including a mixture of
4,4'-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (abbreviation: NPB
or .alpha.-NPB) and a vanadium oxide, or NPB and a molybdenum
oxide, has an absorption band at around 500 nm, in addition to an
absorption band at around 1300 nm. This is a great disadvantage for
optical devices such as light-emitting elements.
[0097] The present inventors have found that a composite material
of a heterocyclic compound having a dibenzofuran skeleton or a
dibenzothiophene skeleton and an electron-accepting inorganic
compound, or the heterocyclic compound and a transition metal
oxide, can exhibit excellent carrier-transport and/or
carrier-injection properties despite the fact that no light
absorption based on charge transfer interaction can be observed
(light absorption hardly occurs). It has been considered that holes
and electrons generated due to charge transfer interaction are
elements for exhibiting carrier-transport and/or carrier-injection
properties; therefore, it can be said that the present invention,
which can provide excellent carrier-transport and/or
carrier-injection properties despite the fact that no clear light
absorption due to charge transfer interaction is observed, is
inconsistent with the general theory and provides an unexpected,
remarkable function.
[0098] Furthermore, dibenzothiophene or dibenzofuran has a large
energy gap in itself. Therefore, by including a dibenzofuran
skeleton or a dibenzothiophene skeleton, the heterocyclic compound
can be designed so as not to have an absorption peak in the visible
light region. Accordingly, there is a great advantage in tern's of
improving a light-transmitting property.
[0099] Moreover, cyclic voltammetry (CV) measurement shows that the
HOMO level of dibenzothiophene or dibenzofuran is lower than or
equal to -6 eV which is extremely low. Therefore, it can be
considered that a heterocyclic compound including a dibenzofuran
skeleton or a dibenzothiophene skeleton by itself has an excellent
hole-injection property to another organic compound, but has
difficulty receiving holes from a conductive material typified by
Al or ITO (having a work function of approximately 3 eV to 5 eV).
On the other hand, by formation of such a composite material as in
one embodiment of the present invention, it becomes possible to
overcome the problem of a hole-injection property from an electrode
while maintaining an excellent hole-injection property to another
organic compound. Such properties of the composite material
contribute to a reduction in drive voltage when the composite
material is used for a light-emitting element. Its high
light-transmitting property enables emission efficiency to
increase. Furthermore, it can be considered that its deep HOMO
level prevents carrier accumulation in a light-emitting element;
thus, a longer lifetime can be achieved.
[0100] Embodiments of the present invention will be described below
with specific examples.
Embodiment 1
[0101] In this embodiment, a composite material of one embodiment
of the present invention will be described.
[0102] A composite material of one embodiment of the present
invention is a composite material of an organic compound having a
particular skeleton and an inorganic compound. There is no
limitation for a preparation method of the composite material of
one embodiment of the present invention; for example, it can be
formed by a co-evaporation method where the organic compound and
the inorganic compound are deposited at the same time. The mixing
ratio, in mass ratio, of the organic compound to the inorganic
compound in the composite material of one embodiment of the present
invention is preferably approximately 8:1 to 1:2 (=organic
compound:inorganic compound), and more desirably, 4:1 to 1:1
(=organic compound:inorganic compound). When the composite material
is formed by a co-evaporation method, the mixing ratio can be
controlled by separately adjusting the deposition rates for the
organic compound and the inorganic compound.
[0103] First, an organic compound that can be used for the
composite material of one embodiment of the present invention is a
heterocyclic compound having a dibenzothiophene skeleton or a
dibenzofuran skeleton.
[0104] With the use of this heterocyclic compound for a composite
material, a material having a high carrier-transport property can
be obtained. In addition, a material having a high
carrier-injection property to an organic compound can be obtained.
Furthermore, a material in which light absorption due to charge
transfer interaction with an inorganic compound is unlikely to
occur can be obtained. Moreover, with the use of the heterocyclic
compound for a composite material, a material having a high
light-transmitting property can be obtained.
[0105] In particular, it is preferable to use a heterocyclic
compound having a substituent having 6 to 70 carbon atoms bonded to
the 4-position of a dibenzothiophene skeleton or a dibenzofuran
skeleton. This is because the occurrence of light absorption based
on charge transfer interaction can be suppressed by use of a
heterocyclic compound having a substituent at the 4-position of a
dibenzothiophene skeleton or a dibenzofuran skeleton for a
composite material. In the case where dibenzothiophene or
dibenzofuran has a bulky substituent (for example, having 6 or more
carbon atoms) at the 4-position, the molecule as a whole is a
steric skeleton due to steric hindrance between dibenzothiophene or
dibenzofuran and the substituent. This stabilizes the film quality
of the composite material. When the composite material is prepared,
it is preferable to co-evaporate the heterocyclic compound and an
inorganic compound, in which case it is desirable that the
heterocyclic compound easily vaporizes. Therefore, in terms of
molecular weight, it is preferable that the number of carbon atoms
of the substituent be less than or equal to 70. Note that it is
preferable that the molecular weight of the heterocyclic compound
be approximately less than or equal to 1200.
[0106] Note that as a result of experiments and studies conducted
by the present inventors, it has been found that a composite
material formed by combining an aromatic hydrocarbon compound
(e.g., an anthracene compound) and an inorganic compound is easily
crystallized when the mixing ratio of the inorganic compound to the
aromatic compound is low. On the contrary, when the mixing ratio of
the inorganic compound is high, although crystallization can be
suppressed, a slight absorption peak resulting from charge transfer
interaction between a skeleton of the aromatic hydrocarbon compound
(e.g., an anthracene skeleton) and the inorganic compound is
increased in the visible light region. On the other hand, in the
case of using a heterocyclic compound having a substituent bonded
to the 4-position of a dibenzothiophene skeleton or a dibenzofuran
skeleton according to one embodiment of the present invention,
crystallization of a composite material can be suppressed and the
film quality of the composite material can be stabilized even when
the substituent includes an anthracene skeleton and the ratio of
the inorganic compound is low, for example. Therefore, in the case
of the composite material of one embodiment of the present
invention, even when the heterocyclic compound includes an
anthracene skeleton, there is no need to increase the ratio of the
inorganic compound for the purpose of suppressing crystallization,
and it is possible to prevent an absorption peak resulting from
charge transfer interaction from being observed in the visible
light region.
[0107] In addition, as a result of experiments and studies
conducted by the present inventors, it has been found that a
composite material formed by combining an aryl carbazole compound
and an inorganic compound is also easily crystallized when the
mixing ratio of the inorganic compound to the aryl carbazole
compound is low. On the contrary, when the ratio of the inorganic
compound is high, although crystallization can be suppressed, a
slight absorption peak resulting from charge transfer interaction
between the aryl carbazole skeleton and the inorganic compound is
increased in the visible light region. On the other hand, in the
case of using a heterocyclic compound having a substituent bonded
to the 4-position of a dibenzothiophene skeleton or a dibenzofuran
skeleton according to one embodiment of the present invention,
crystallization of a composite material can be suppressed and the
film quality of the composite material can be stabilized even when
the substituent includes an aryl carbazole skeleton and the ratio
of the inorganic compound is low, for example. Therefore, in the
case of the composite material of one embodiment of the present
invention, even when the heterocyclic compound includes an aryl
carbazole skeleton, there is no need to increase the ratio of the
inorganic compound for the purpose of suppressing crystallization,
and it is possible to prevent an absorption peak resulting from
charge transfer interaction from being observed in the visible
light region.
[0108] It is preferable that a ring of the substituent be one or a
plurality of rings selected from a benzene ring, a naphthalene
ring, a phenanthrene ring, a triphenylene ring, a fluorene ring, a
dibenzothiophene ring, and a dibenzofuran ring. Each of these rings
is an important conjugate ring for exhibiting a carrier-transport
property (especially, a hole-transport property) and is at the same
time a conjugate ring having a wide energy gap. Accordingly, when
the ring of the substituent is limited to these rings, it is
possible not only to suppress the occurrence of light absorption
based on charge transfer interaction but also to control an
absorption peak of the heterocyclic compound so as to appear at a
shorter wavelength than the visible light region. Thus, with the
use of the heterocyclic compound, a composite material having a
high light-transmitting property can be obtained.
[0109] It is particularly preferable that a ring of the substituent
be one or a plurality of rings selected from a benzene ring, a
fluorene ring, a dibenzothiophene ring, and a dibenzofuran ring.
The present inventors have found that in this case, light
absorption based on charge transfer interaction with the organic
compound hardly occurs. In particular, light absorption due to
charge transfer interaction hardly occurs even with a high mixing
ratio of the inorganic compound to the heterocyclic compound.
Specifically, light absorption based on charge transfer interaction
hardly occurs even when the mixing ratio, in mass ratio, of the
heterocyclic compound to the inorganic compound is in the range
from 4:1 to 1:1 (=heterocyclic compound:inorganic compound). Note
that it is preferable that the concentration of the inorganic
compound be high because the conductivity of the composite material
also becomes high. The present inventors have also found that the
composite material of one embodiment of the present invention can
exhibit favorable carrier-transport and/or carrier-injection
properties, and favorable reliability when used for a
light-emitting element despite the fact that light absorption due
to charge transfer interaction hardly occurs.
[0110] In addition, it is preferable to use a heterocyclic compound
having a phenyl group bonded to the 4-position of a
dibenzothiophene skeleton or a dibenzofuran skeleton, in which the
phenyl group has one or more substituents and the phenyl group and
the one or more substituents have a total of 12 to 70 carbon atoms.
This is because the occurrence of light absorption based on charge
transfer interaction can be suppressed by use of a heterocyclic
compound having a phenyl group with small conjugation bonded to the
4-position of a dibenzothiophene skeleton or a dibenzofuran
skeleton for a composite material. In addition, since the phenyl
group has small conjugation, even when the molecular weight is
increased by bonding an additional substituent to the phenyl group,
a wide energy gap can be maintained, which is also effective in
terms of improving a light-transmitting property. Furthermore, in
the case where dibenzothiophene or dibenzofuran has a bulky site
(for example, a skeleton having a total of 12 or more carbon atoms
including the phenyl group) at the 4-position, the molecule as a
whole is a steric skeleton due to steric hindrance between
dibenzothiophene or dibenzofuran and the bulky site. This
stabilizes the film quality of the composite material. When the
composite material is prepared, it is preferable to co-evaporate
the heterocyclic compound and an inorganic compound, in which case
it is desirable that the heterocyclic compound easily vaporizes.
Therefore, in terms of molecular weight, it is preferable that the
sum of carbon atoms of the bulky site be less than or equal to 70.
Note that it is preferable that the molecular weight of the
heterocyclic compound be approximately less than or equal to
1200.
[0111] It is preferable that a ring of the one or more substituents
be separately one or a plurality of rings selected from a benzene
ring, a naphthalene ring, a phenanthrene ring, a triphenylene ring,
a fluorene ring, a dibenzothiophene ring, and a dibenzofuran ring.
Each of these rings is an important conjugate ring for exhibiting a
carrier-transport property (especially, a hole-transport property),
and in addition, it is a conjugate ring having a wide energy gap.
Accordingly, when the ring of the one or more substituents is
limited to these rings, it is possible not only to suppress the
occurrence of light absorption based on charge transfer interaction
but also to control an absorption peak of the heterocyclic compound
so as to appear at a shorter wavelength than the visible light
region. Thus, with the use of the heterocyclic compound, a
composite material having a high light-transmitting property can be
obtained.
[0112] It is particularly preferable that a ring of the one or more
substituents be separately one or a plurality of rings selected
from a benzene ring, a fluorene ring, a dibenzothiophene ring, and
a dibenzofuran ring. The present inventors have found that in this
case, light absorption based on charge transfer interaction with
the organic compound hardly occurs. In particular, light absorption
due to charge transfer interaction hardly occurs even with a high
mixing ratio of the inorganic compound to the heterocyclic
compound. Specifically, light absorption based on charge transfer
interaction hardly occurs even when the mixing ratio, in mass
ratio, of the heterocyclic compound to the inorganic compound is in
the range from 4:1 to 1:1 (=heterocyclic compound:inorganic
compound). Note that it is preferable that the concentration of the
inorganic compound be high because the conductivity of the
composite material also becomes high. The present inventors have
also found that the composite material of one embodiment of the
present invention can exhibit favorable carrier-transport and/or
carrier-injection properties, and favorable reliability when used
for a light-emitting element despite the fact that light absorption
due to charge transfer interaction hardly occurs.
[0113] Another organic compound that can be used for the composite
material of one embodiment of the present invention is a
heterocyclic compound represented by a general formula (G1).
##STR00003##
[0114] In the general formula (G1), A represents oxygen or sulfur;
R.sup.1 to R.sup.7 separately represent hydrogen, an alkyl group
having 1 to 4 carbon atoms, or an aryl group having 6 to 25 carbon
atoms in a ring; R.sup.8 to R.sup.12 separately represent hydrogen,
a substituted or unsubstituted phenyl group, a substituted or
unsubstituted naphthyl group, a substituted or unsubstituted
phenanthryl group, a substituted or unsubstituted triphenylenyl
group, a substituted or unsubstituted fluorenyl group, a
substituted or unsubstituted dibenzothiophenyl group, or a
substituted or unsubstituted dibenzofuranyl group. Note that at
least one of R.sup.8 to R.sup.12 represents a substituted or
unsubstituted phenyl group, a substituted or unsubstituted naphthyl
group, a substituted or unsubstituted phenanthryl group, a
substituted or unsubstituted triphenylenyl group, a substituted or
unsubstituted fluorenyl group, a substituted or unsubstituted
dibenzothiophenyl group, or a substituted or unsubstituted
dibenzofuranyl group.
[0115] It is particularly preferable that R.sup.8 to R.sup.12
separately represent hydrogen, a substituted or unsubstituted
phenyl group, a substituted or unsubstituted fluorenyl group, a
substituted or unsubstituted dibenzothiophenyl group, or a
substituted or unsubstituted dibenzofuranyl group. Note that at
least one of R.sup.8 to R.sup.12 represents a substituted or
unsubstituted phenyl group, a substituted or unsubstituted
fluorenyl group, a substituted or unsubstituted dibenzothiophenyl
group, or a substituted or unsubstituted dibenzofuranyl group.
[0116] Examples of organic compounds that can be used for the
composite material of one embodiment of the present invention are
represented by the following structural formulae (100) to
(128).
##STR00004##
[0117] Next, an inorganic compound that can be used for the
composite material of one embodiment of the present invention will
be described.
[0118] An inorganic compound exhibiting an electron-accepting
property with respect to the heterocyclic compound used for the
composite material of one embodiment of the present invention can
be used. Iron(III) chloride, aluminum chloride, and the like are
examples of inorganic compounds having a high electron-accepting
property.
[0119] Alternatively, a transition metal oxide can be used as an
inorganic compound for the composite material of one embodiment of
the present invention. It is preferable to use an oxide of a metal
belonging to any of Groups 4 to 8 of the periodic table. It is
particularly preferable to use titanium oxide, vanadium oxide,
tantalum oxide, molybdenum oxide, tungsten oxide, rhenium oxide,
ruthenium oxide, chromium oxide, zirconium oxide, hafnium oxide, or
silver oxide. Molybdenum oxide is particularly easy to handle among
them, because it is easily deposited, has a low hygroscopic
property, and is stable.
[0120] A transition metal oxide is considered not to have a very
high electron-accepting property (considered to have low
reactivity), as compared to a strong Lewis acid such as iron(III)
chloride mentioned above. In the composite material of one
embodiment of the present invention, as described above, the
occurrence of light absorption based on charge transfer interaction
is suppressed (or light absorption hardly occurs). It is difficult
to prove from these that a transition metal oxide acts as an
electron acceptor in a general sense in the present invention. On
the other hand, as described in the following examples, there is an
experimental fact that the composite material of one embodiment of
the present invention conducts a larger amount of current than the
heterocyclic compound alone can do, when an electric field is
applied. Thus, when a transition metal oxide is used in the
composite material of one embodiment of the present invention, it
can be considered that carriers are easily generated at least with
an assistance of application of an electric field. Therefore, in
this specification, an inorganic compound (such as a transition
metal oxide mentioned above) in the composite material is regarded
as having an electron-accepting property as long as carriers are
generated at least with an assistance of application of an electric
field.
[0121] It is preferable that the HOMO level of the heterocyclic
compound included in the above-described composite material of one
embodiment of the present invention, which is measured by
photoelectron spectrometry, be lower than or equal to -5.7 eV. As
described above, CV measurement shows that the HOMO level of
dibenzothiophene or dibenzofuran is lower than or equal to -6 eV
which is extremely low. Therefore, the HOMO level of a heterocyclic
compound alone including a dibenzofuran skeleton or a
dibenzothiophene skeleton can easily be made as low as or lower
than -5.7 eV.
[0122] In the case where the heterocyclic compound has a low HOMO
level, it can be considered that the heterocyclic compound has an
excellent hole-injection property to another organic compound, but
has difficulty receiving holes from a conductive material typified
by Al or ITO (having a work function of approximately 3 eV to 5
eV). On the other hand, by formation of such a composite material
as in one embodiment of the present invention, it is possible to
overcome the problem of a hole-injection property from an electrode
while maintaining an excellent hole-injection property to another
organic compound. Such properties of the composite material
contribute to a reduction in drive voltage when the composite
material is used for a light-emitting element. Its high
light-transmitting property enables emission efficiency to
increase. Furthermore, its deep HOMO level can prevent carrier
accumulation; thus, a longer lifetime can be achieved.
[0123] As described above, the composite material of one embodiment
of the present invention is a material having a low HOMO level and
a high carrier-transport property. In addition, the composite
material of one embodiment of the present invention is a material
having an excellent carrier-injection property to an organic
compound. Furthermore, the composite material of one embodiment of
the present invention is a material in which light absorption based
on charge transfer interaction is unlikely to occur.
[0124] Therefore, the composite material of one embodiment of the
present invention can be used for a light-emitting element or a
semiconductor element such as a photoelectric conversion element or
a transistor.
[0125] Furthermore, the composite material of one embodiment of the
present invention has an excellent carrier-transport property and
an excellent carrier-injection property to an organic compound and
can therefore reduce drive voltage when used for a light-emitting
element or the like.
[0126] The composite material of one embodiment of the present
invention has a light-transmitting property and can therefore
realize high emission efficiency when used for a light-emitting
element or the like.
[0127] The composite material of one embodiment of the present
invention suppresses charge accumulation and can therefore realize
an element having a long lifetime when used for a light-emitting
element or the like.
[0128] Note that this embodiment can be implemented in appropriate
combination with any of the other embodiments.
Embodiment 2
[0129] In this embodiment, a light-emitting element of one
embodiment of the present invention will be described with
reference to FIGS. 1A to 1C.
[0130] In a light-emitting element of this embodiment, an EL layer
(a layer containing a light-emitting substance) is interposed
between a pair of electrodes. The EL layer includes at least a
layer containing the composite material of one embodiment of the
present invention described in Embodiment 1 and a light-emitting
layer. The EL layer may additionally include another layer. For
example, the EL layer may include a layer containing a substance
having a high carrier-injection property or a layer containing a
substance having a high carrier-transport property so that a
light-emitting region is formed in a region away from the
electrodes, that is, so that carriers recombine in a region away
from the electrodes. In this specification, the layer containing a
substance having a high carrier-injection or a high
carrier-transport property is also called a functional layer which
functions, for instance, to inject or transport carriers. As a
functional layer, a hole-injection layer, a hole-transport layer,
an electron-injection layer, an electron-transport layer, or the
like can be used. Note that in this embodiment, the layer
containing the composite material of one embodiment of the present
invention is used as a hole-injection layer.
[0131] It is preferable that one or more layers (such as a
hole-transport layer) be provided between the layer containing the
composite material of one embodiment of the present invention and
the light-emitting layer. Accordingly, it is possible to suppress
quenching (a decrease in efficiency) caused by transfer of
excitation energy generated in the light-emitting layer to the
layer containing the composite material, and it is possible to
obtain a more efficient element.
[0132] In the light-emitting element illustrated in FIG. 1A, an EL
layer 102 is provided between a first electrode 101 and a second
electrode 108. In the EL layer 102, a hole-injection layer 701, a
hole-transport layer 702, a light-emitting layer 703, an
electron-transport layer 704, and an electron-injection layer 705
are stacked in this order over the first electrode 101. Note that,
in the light-emitting element described in this embodiment, the
first electrode 101 functions as an anode and the second electrode
108 functions as a cathode.
[0133] As a support of the light-emitting element (see a substrate
100 in FIG. 1A), a glass substrate, a quartz substrate, a plastic
substrate, or the like can be used, for example. Furthermore, a
flexible substrate may be used. The flexible substrate is a
substrate that can be bent, such as a plastic substrate made of
polycarbonate, polyarylate, or polyether sulfone, for example. A
film (made of polypropylene, polyester, vinyl, polyvinyl fluoride,
vinyl chloride, or the like), an inorganic film formed by
evaporation, or the like can also be used. Note that materials
other than these can be used as long as they can function as a
support of the light-emitting element.
[0134] For the first electrode 101, any of a variety of metals,
alloys, conductive compounds, mixtures thereof, and the like can be
used. Examples include indium oxide-tin oxide (ITO: indium tin
oxide), indium oxide-tin oxide containing silicon or silicon oxide,
indium oxide-zinc oxide (IZO: indium zinc oxide), indium oxide
containing tungsten oxide and zinc oxide (IWZO), and the like.
Films of these conductive metal oxides are usually formed by
sputtering, but may be formed by application of a sol-gel method or
the like. For example, an IZO film can be formed by a sputtering
method using a target obtained by adding 1 wt % to 20 wt % of zinc
oxide to indium oxide. Further, an IWZO film can be formed by a
sputtering method using a target obtained by adding 0.5 wt % to 5
wt % of tungsten oxide and 0.1 wt % to 1 wt % of zinc oxide to
indium oxide. Other examples are gold, platinum, nickel, tungsten,
chromium, molybdenum, iron, cobalt, copper, palladium, nitrides of
metal materials (e.g., titanium nitride), and the like.
[0135] As a material of the first electrode 101, it is preferable
to use a material having a high work function (a work function
higher than or equal to 4.0 eV). Note that in a light-emitting
element having a structure where the first electrode 101 and the
layer containing the composite material of one embodiment of the
present invention are in contact with each other, a material used
for the first electrode 101 is not limited to a material having a
high work function and can be a material having a low work
function. For example, aluminum, silver, an alloy including
aluminum (e.g., Al--Si), or the like can also be used.
[0136] The hole-injection layer 701 is a layer that contains the
composite material of one embodiment of the present invention.
[0137] The heterocyclic compound (see Embodiment 1) used for the
composite material of one embodiment of the present invention has a
low HOMO level and an excellent hole-injection property to the
hole-transport layer 702 and the light-emitting layer 703. On the
other hand, an injection barrier is generated between the first
electrode 101 and the heterocyclic compound, and holes are not
easily injected from the first electrode 101.
[0138] However, in the light-emitting element of one embodiment of
the present invention, the composite material of one embodiment of
the present invention (a material including the heterocyclic
compound and an inorganic compound exhibiting an electron-accepting
property with respect to the heterocyclic compound) is used for the
hole-injection layer 701; thus, the injection barrier between the
first electrode 101 and the hole-injection layer 701 can be
reduced. Therefore, it is possible to realize an element having a
low injection barrier from the first electrode 101 to the
light-emitting layer 703 and a high carrier-injection property, and
it is possible to provide a light-emitting element having a low
drive voltage.
[0139] Furthermore, the composite material of one embodiment of the
present invention has high carrier-generation efficiency and a high
carrier-transport property. Therefore, with the use of the
composite material of one embodiment of the present invention, it
is possible to realize a light-emitting element having high
emission efficiency.
[0140] In addition, with the heterocyclic compound, a high
absorption peak is not generated in the visible light region.
Furthermore, the heterocyclic compound has a low HOMO level, and
light absorption based on charge transfer interaction with the
inorganic compound is unlikely to occur. Thus, in the composite
material of one embodiment of the present invention, an absorption
peak in the visible light region is unlikely to be generated, and
the composite material has a high light-transmitting property.
Therefore, this also shows that with the use of the composite
material of one embodiment of the present invention, it is possible
to realize a light-emitting element having high emission
efficiency.
[0141] The composite material of one embodiment of the present
invention can suppress charge accumulation; therefore, a
light-emitting element having a long lifetime can be provided.
[0142] The hole-transport layer 702 is a layer that contains a
substance having a high hole-transport property. As a material of
the hole-transport layer 702, the heterocyclic compound used for
the composite material of one embodiment of the present invention
may be used. Other examples of the substance having a high
hole-transport property are aromatic amine compounds such as
4,4'-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (abbreviation: NPB
or .alpha.-NPB),
N,N'-bis(3-methylphenyl)-N,N'-diphenyl-[1,1'-biphenyl]-4,4'-diamine
(abbreviation: TPD),
4-phenyl-4'-(9-phenylfluoren-9-yl)triphenylamine (abbreviation:
BPAFLP),
4,4'-bis[N-(9,9-dimethylfluoren-2-yl)-N-phenylamino]biphenyl
(abbreviation: DFLDPBi), and
4,4'-bis[N-(spiro-9,9'-bifluoren-2-yl)-N-phenylamino]biphenyl
(abbreviation: BSPB). The substances mentioned here are mainly
substances that have a hole mobility of 10.sup.-6 cm.sup.2/Vs or
more. Note that other than these substances, any substance that has
a property of transporting more holes than electrons may be used.
Note that the layer containing a substance having a high
hole-transport property is not limited to a single layer, and may
be a stack of two or more layers containing any of the above
substances.
[0143] For the hole-transport layer 702, a carbazole derivative
such as 4,4'-di(N-carbazolyl)biphenyl (abbreviation: CBP),
9-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazole (abbreviation:
CzPA), or 9-phenyl-3-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazole
(abbreviation: PCzPA) or an anthracene derivative such as
2-tert-butyl-9,10-di(2-naphthyl)anthracene (abbreviation: t-BuDNA),
9,10-di(2-naphthyl)anthracene (abbreviation: DNA), or
9,10-diphenylanthracene (abbreviation: DPAnth) may be used.
[0144] In particular, the heterocyclic compound in the composite
material of one embodiment of the present invention has a low HOMO
level; therefore, a material having a low HOMO level can be used
also for the hole-transport layer. With such a structure, it is
possible to prevent charge accumulation at the interface between
the light-emitting layer and the hole-transport layer, and it is
possible to extend the lifetime of the light-emitting element.
Specifically, it is preferable that the HOMO level of the
hole-transport layer be lower than or equal to -5.6 eV. From such a
point of view, a carbazole derivative, a dibenzothiophene
derivative, a dibenzofuran derivative, an anthracene derivative, or
the like is preferable as a compound that is used for the
hole-transport layer.
[0145] Note that for the hole-transport layer 702, a high molecular
compound such as poly(N-vinylcarbazole) (abbreviation: PVK),
poly(4-vinyltriphenylamine) (abbreviation: PVTPA),
poly[N-(4-N'-[4-(4-diphenylamino)phenyl]phenyl-N'-phenylamino}phenyl)meth-
acrylamide] (abbreviation: PTPDMA), or
poly[N,N'-bis(4-butylphenyl)-N,N'-bis(phenyl)benzidine]
(abbreviation: Poly-TPD) can also be used.
[0146] The light-emitting layer 703 is a layer that contains a
light-emitting organic compound. As the light-emitting organic
compound, for example, a fluorescent compound which emits
fluorescence or a phosphorescent compound which emits
phosphorescence can be used.
[0147] Examples of a fluorescent compound that can be used for the
light-emitting layer 703 are the following light-emitting
materials, for example: materials that emit blue light, such as
N,N'-bis[4-(9H-carbazol-9-yl)phenyl]-N,N'-diphenylstilbene-4,4'-diamine
(abbreviation: YGA2S),
4-(9H-carbazol-9-yl)-4'-(10-phenyl-9-anthryl)triphenylamine
(abbreviation: YGAPA), and
4-(10-phenyl-9-anthryl)-4'-(9-phenyl-9H-carbazol-3-yl)triphenylamine
(abbreviation: PCBAPA); materials that emit green light, such as
N-(9,10-diphenyl-2-anthryl)-N,9-diphenyl-9H-carbazol-3-amine
(abbreviation: 2PCAPA),
N-[9,10-bis(1,1'-biphenyl-2-yl)-2-anthryl]-N,9-diphenyl-9H-carbazol-3-ami-
ne (abbreviation: 2PCABPhA),
N-(9,10-diphenyl-2-anthryl)-N,N',N'-triphenyl-1,4-phenylenediamine
(abbreviation: 2DPAPA),
N-[9,10-bis(1,1'-biphenyl-2-yl)-2-anthryl]-N,N',N'-triphenyl-1,4-phenylen-
ediamine (abbreviation: 2DPABPhA),
N-[9,10-bis(1,1'-biphenyl-2-yl)]-N-[4-(9H-carbazol-9-yl)phenyl]-N-phenyla-
nthracen-2-amine (abbreviation: 2YGABPhA), and
N,N,9-triphenylanthracen-9-amine (abbreviation: DPhAPhA); materials
that emit yellow light, such as rubrene and
5,12-bis(1,1'-biphenyl-4-yl)-6,11-diphenyltetracene (abbreviation:
BPT); and materials that emit red light, such as
N,N,N',N'-tetrakis(4-methylphenyl)tetracene-5,11-diamine
(abbreviation: p-mPhTD) and
7,14-diphenyl-N,N,N',N'-tetrakis(4-methylphenyl)acenaphtho[1,2-a]fluorant-
hene-3,10-diamine (abbreviation: p-mPhAFD).
[0148] Examples of a phosphorescent compound that can be used for
the light-emitting layer 703 are the following light-emitting
materials, for example: materials that emit blue light, such as
bis[2-(4',6'-difluorophenyl)pyridinato-N,C.sup.2']iridium(III)tetrakis(1--
pyrazolyl)borate (abbreviation: FIr6),
bis[2-(4',6'-difluorophenyl)pyridinato-N,C.sup.2']iridium(III)picolinate
(abbreviation: FIrpic),
bis{2-[3',5'-bis(trifluoromethyl)phenyl]pyridinato-N.sup.2'},
iridium(III)picolinate (abbreviation: Ir(CF.sub.3ppy).sub.2(pic)),
and
bis[2-(4',6'-difluorophenyl)pyridinato-N,C.sup.2']iridium(III)acetylaceto-
nate (abbreviation: FIr(acac)); materials that emit green light,
such as tris(2-phenylpyridinato-N,C.sup.2')iridium(III)
(abbreviation: Ir(ppy).sub.3),
bis(2-phenylpyridinato-N,C.sup.2')iridium(III)acetylacetonate
(abbreviation: Ir(ppy).sub.2(acac)),
bis(1,2-diphenyl-1H-benzimidazolato)iridium(III)acetylacetonate
(abbreviation: Ir(pbi).sub.2(acac)),
bis(benzo[h]quinolinato)iridium(III)acetylacetonate (abbreviation:
Ir(bzq).sub.2(acac)), and tris(benzo[h]quinolinato)iridium(III)
(abbreviation: Ir(bzq).sub.3); materials that emit yellow light,
such as bis(2,4-diphenyl-1,3-oxazolato-N,C.sup.2')iridium (III)
acetyl acetonate (abbreviation: Ir(dpo).sub.2(acac)),
bis[2-(4'-(perfluorophenylphenyl)pyridinato]iridium(III)acetylacetonate
(abbreviation: Ir(p-PF-ph).sub.2(acac)),
bis(2-phenylbenzothiazolato-N,C.sup.2') iridium(III)acetylacetonate
(abbreviation: Ir(bt).sub.2(acac)),
(acetylacetonato)bis[2,3-bis(4-fluorophenyl)-5-methylpyrazinato]iridium(I-
II) (abbreviation: Ir(Fdppr-Me).sub.2(acac)), and
(acetylacetonato)bis{2-(4-methoxyphenyl)-3,5-dimethylpyrazinato}iridium(I-
II) (abbreviation: Ir(dmmoppr).sub.2(acac)); materials that emit
orange light, such as
tris(2-phenylquinolinato-N,C.sup.2')iridium(III) (abbreviation:
Ir(pq).sub.3),
bis(2-phenylquinolinato-N,C.sup.2')iridium(III)acetylacetonate
(abbreviation: Ir(pq).sub.2(acac)),
(acetylacetonato)bis(3,5-dimethyl-2-phenylpyrazinato)iridium(III)
(abbreviation: Ir(mppr-Me).sub.2(acac)), and
(acetylacetonato)bis(5-isopropyl-3-methyl-2-phenylpyrazinato)iridium
(III) (abbreviation: Ir(mppr-iPr).sub.2(acac)); and materials that
emit red light, for example, organometallic complexes, such as
bis[2-(2'-benzo[4,5-.alpha.]thienyl)pyridinato-N,C.sup.3')iridium(III)ace-
tylacetonate (abbreviation: Ir(btp).sub.2(acac)),
bis(1-phenylisoquinolinato-N,C.sup.2')iridium(III)acetylacetonate
(abbreviation: Ir(piq).sub.2(acac),
(acetylacetonato)bis[2,3-bis(4-fluorophenyl)quinoxalinato]iridium(III)
(abbreviation: Ir(Fdpq).sub.2(acac)),
(acetylacetonato)bis(2,3,5-triphenylpyrazinato)iridium(III)
(abbreviation: Ir(tppr).sub.2(acac)),
(dipivaloylmethanato)bis(2,3,5-triphenylpyrazinato)iridium (III)
(abbreviation: Ir(tppr).sub.2(dpm)), and (2,3,7,
8,12,13,17,18-octaethyl-21H,23H-porphyrin)platinum(II)
(abbreviation: PtOEP). Any of the following rare earth metal
complexes can be used as a phosphorescent compound:
tris(acetylacetonato)(monophenanthroline)terbium(III)
(abbreviation: Tb(acac).sub.3(Phen));
tris(1,3-diphenyl-1,3-propanedionato)(monophenanthroline)europium(III)
(abbreviation: Eu(DBM).sub.3(Phen)); and
tris[1-(2-thenoyl)-3,3,3-trifluoroacetonato](monophenanthroline)europium(-
III) (abbreviation: Eu(TTA).sub.3(Phen)), because their light
emission is from a rare earth metal ion (electronic transition
between different multiplicities) in such a rare earth metal
complex.
[0149] Note that the light-emitting layer 703 may have a structure
in which any of the above-described light-emitting organic
compounds (a guest material) is dispersed into another substance (a
host material). A variety of substances can be used as the host
material, and it is preferable to use a substance having a lowest
unoccupied molecular orbital level (LUMO level) higher than that of
a light-emitting substance and having a HOMO level lower than that
of the light-emitting substance.
[0150] Specific examples of the host material that can be used are
the following materials: metal complexes, such as
tris(8-quinolinolato)aluminum(III) (abbreviation: Alq),
tris(4-methyl-8-quinolinolato)aluminum(III) (abbreviation:
Almq.sub.3), bis(10-hydroxybenzo[h]quinolinato)beryllium(II)
(abbreviation: BeBq.sub.2),
bis(2-methyl-8-quinolinolato)(4-phenylphenolato)aluminum(III)
(abbreviation: BAlq), bis(8-quinolinolato)zinc(II) (abbreviation:
Znq), bis[2-(2-benzoxazolyl)phenolato]zinc(II) (abbreviation:
ZnPBO), and bis[2-(2-benzothiazolyl)phenolato]zinc(II)
(abbreviation: ZnBTZ); heterocyclic compounds, such as
2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole
(abbreviation: PBD),
1,3-bis[5-(p-tert-butylphenyl)-1,3,4-oxadiazol-2-yl]benzene
(abbreviation: OXD-7),
3-(4-biphenylyl)-4-phenyl-5-(4-tert-butylphenyl)-1,2,4-triazole
(abbreviation: TAZ),
2,2',2''-(1,3,5-benzenetriyl)tris(1-phenyl-1H-benzimidazole)
(abbreviation: TPBI), bathophenanthroline (abbreviation: BPhen),
and bathocuproine (BCP); condensed aromatic compounds, such as
9-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazole (abbreviation:
CzPA), 3,6-diphenyl-9-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazole
(abbreviation: DPCzPA), 9,10-bis(3,5-diphenylphenyl)anthracene
(abbreviation: DPPA), 9,10-di(2-naphthyl)anthracene (abbreviation:
DNA), 2-tert-butyl-9,10-di(2-naphthyl)anthracene (abbreviation:
t-BuDNA), 9,9'-bianthryl (abbreviation: BANT),
9,9'-(stilbene-3,3'-diyl)diphenanthrene (abbreviation: DPNS),
9,9'-(stilbene-4,4'-diyl)diphenanthrene (abbreviation: DPNS2),
3,3',3''-(benzene-1,3,5-triyl)tripyrene (abbreviation: TPB 3),
9,10-diphenylanthracene (abbreviation: DPAnth), and
6,12-dimethoxy-5,11-diphenylchrysene; aromatic amine compounds,
such as
N,N-diphenyl-9-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazol-3-amine
(abbreviation: CzAlPA), 4-(10-phenyl-9-anthryl)triphenylamine
(abbreviation: DPhPA),
N,9-diphenyl-N-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazol-3-amine
(abbreviation: PCAPA),
N,9-diphenyl-N-{4-[4-(10-phenyl-9-anthryl)phenyl]phenyl}-9H-carbazol-3-am-
ine (abbreviation: PCAPBA),
N-(9,10-diphenyl-2-anthryl)-N,9-diphenyl-9H-carbazol-3-amine
(abbreviation: 2PCAPA), NPB (or .alpha.-NPD), TPD, DFLDPBi, and
BSPB; and the like.
[0151] Plural kinds of host materials can also be used. For
example, in order to suppress crystallization, a substance such as
rubrene which suppresses crystallization, may be further added. In
addition, NPB, Alq, or the like may be further added in order to
efficiently transfer energy to the guest material.
[0152] With a structure in which a guest material is dispersed in a
host material, crystallization of the light-emitting layer 703 can
be suppressed. In addition, concentration quenching due to high
concentration of the guest material can also be suppressed.
[0153] For the light-emitting layer 703, a high molecular compound
can be used. Specific examples of blue light-emitting materials are
poly(9,9-dioctylfluorene-2,7-diyl) (abbreviation: PFO),
poly[(9,9-di
octylfluorene-2,7-diyl)-co-(2,5-dimethoxybenzene-1,4-diyl)]
(abbreviation: PF-DMOP),
poly{(9,9-dioctylfluorene-2,7-diyl)-co-[N,N'-di-(p-butylphenyl)-1,4-diami-
nobenzene]} (abbreviation: TAB-PFH), and the like. Specific
examples of green light-emitting materials are
poly(p-phenylenevinylene) (abbreviation: PPV),
poly[(9,9-dihexylfluorene-2,7-diyl)-alt-co-(benzo[2,1,3]thiadiazole-4,7-d-
iyl)] (abbreviation: PFBT),
poly[(9,9-dioetyl-2,7-divinylenefluorenylene)-alt-co-(2-methoxy-5-(2-ethy-
lhexyloxy)-1,4-phenylene)], and the like. Specific examples of
orange to red light-emitting materials are
poly[2-methoxy-5-(2'-ethylhexoxy)-1,4-phenylenevinylene]
(abbreviation: MEH-PPV), poly(3-butylthiophene-2,5-diyl)
(abbreviation: R4-PAT),
poly{[9,9-dihexyl-2,7-bis(1-cyanovinylene)fluorenylene]-alt-co-[2,5-bis(N-
,N'-diphenyl amino)-1,4-phenylene]},
poly{[2-methoxy-5-(2-ethylhexyloxy)-1,4-bis(1-cyanovinylenephenylene)]-al-
t-co-[2,5-bis(N,N'-diphenylamino)-1,4-phenylene]} (abbreviation:
CN-PPV-DPD), and the like.
[0154] Further, by providing a plurality of light-emitting layers
and making emission colors of the light-emitting layers different,
light emission of a desired color can be obtained from the
light-emitting element as a whole. For example, the emission colors
of first and second light-emitting layers are complementary in a
light-emitting element having the two light-emitting layers, so
that the light-emitting element can be made to emit white light as
a whole. Note that the term "complementary" means color
relationship in which an achromatic color is obtained when colors
are mixed. That is, emission of white light can be obtained by
mixture of light emitted from substances whose emission colors are
complementary colors. Further, the same applies to a light-emitting
element having three or more light-emitting layers.
[0155] The electron-transport layer 704 is a layer that contains a
substance having a high electron-transport property. Examples of
the substance having a high electron-transport property are metal
complexes having a quinoline skeleton or a benzoquinoline skeleton,
such as tris(8-quinolinolato)aluminum (abbreviation: Alq),
tris(4-methyl-8-quinolinolato)aluminum (abbreviation: Almq.sub.3),
bis(10-hydroxybenzo[h]quinolinato)beryllium (abbreviation:
BeBq.sub.2), and
bis(2-methyl-8-quinolinolato)(4-phenylphenolato)aluminum
(abbreviation: BAlq). Other examples are metal complexes having an
oxazole-based or thiazole-based ligand, such as
bis[2-(2-hydroxyphenyl)benzoxazolato]zinc (abbreviation:
Zn(BOX).sub.2) and bis[2-(2-hydroxyphenyl)benzothiazolato]zinc
(abbreviation: Zn(BTZ).sub.2). Other than metal complexes,
2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole
(abbreviation: PBD),
1,3-bis[5-(p-tert-butylphenyl)-1,3,4-oxadiazol-2-yl]benzene
(abbreviation: OXD-7),
3-(4-biphenylyl)-4-phenyl-5-(4-tert-butylphenyl)-1,2,4-triazole
(abbreviation: TAZ), bathophenanthroline (abbreviation: BPhen),
bathocuproine (abbreviation: BCP), or the like can be used. The
substances described here are mainly substances having an electron
mobility of 10.sup.-6 cm.sup.2/Vs or more. Further, the
electron-transport layer is not limited to a single layer, and may
be a stack of two or more layers containing any of the above
substances.
[0156] The electron-injection layer 705 is a layer that contains a
substance having a high electron-injection property. Examples of
the substance that can be used for the electron-injection layer 705
are alkali metals, alkaline earth metals, and compounds thereof,
such as lithium, cesium, calcium, lithium fluoride, cesium
fluoride, calcium fluoride, and lithium oxide, rare earth metal
compounds, such as erbium fluoride, and the above-mentioned
substances for forming the electron-transport layer 704.
[0157] Note that the hole-injection layer 701, the hole-transport
layer 702, the light-emitting layer 703, the electron-transport
layer 704, and the electron-injection layer 705 which are described
above can each be formed by a method, such as an evaporation method
(e.g., a vacuum evaporation method), an inkjet method, or a coating
method.
[0158] In a light-emitting element illustrated in FIG. 2A, the EL
layer 102 is provided between a pair of electrodes, the first
electrode 101 and the second electrode 108, over the substrate 100.
The EL layer 102 includes the hole-injection layer 701, the
hole-transport layer 702, the light-emitting layer 703, the
electron-transport layer 704, and the electron-injection layer 705.
The light-emitting element in FIG. 2A includes the second electrode
108 serving as a cathode over the substrate 100, the
electron-injection layer 705, the electron-transport layer 704, the
light-emitting layer 703, the hole-transport layer 702, and the
hole-injection layer 701 which are stacked over the second
electrode 108 in this order, and the first electrode 101 provided
thereover which serves as an anode.
[0159] Furthermore, by making emission colors of EL layers
different, light of a desired color can be obtained from the
light-emitting element as a whole. For example, the emission colors
of first and second EL layers are complementary in a light-emitting
element having the two EL layers, so that the light-emitting
element can be made to emit white light as a whole. Further, the
same applies to a light-emitting element having three or more EL
layers.
[0160] A plurality of EL layers may be stacked between the first
electrode 101 and the second electrode 108 as illustrated in FIG.
1B. In that case, a charge-generation layer 803 is preferably
provided between a first EL layer 800 and a second EL layer 801
which are stacked. The charge-generation layer 803 can be formed
using the composite material of one embodiment of the present
invention. The composite material of one embodiment of the present
invention has high carrier generation efficiency and a high
hole-transport property at the time of voltage application.
Therefore, with the use of the composite material of one embodiment
of the present invention, it is possible to realize a
light-emitting element having a low drive voltage. In addition, it
is possible to realize a light-emitting element having high
emission efficiency.
[0161] In addition, with the heterocyclic compound, an absorption
peak in the visible light region is unlikely to be generated.
Furthermore, the heterocyclic compound has a low HOMO level, and
light absorption based on charge transfer interaction with the
inorganic compound is unlikely to occur. Thus, in the composite
material of one embodiment of the present invention, an absorption
peak in the visible light region is unlikely to be generated, and
the composite material has a high light-transmitting property.
Therefore, this also shows that with the use of the composite
material of one embodiment of the present invention, it is possible
to realize a light-emitting element having high emission
efficiency.
[0162] Further, the charge-generation layer 803 may have a stacked
structure including a layer containing the composite material of
one embodiment of the present invention and a layer containing
another material. In that case, as the layer containing another
material, a layer containing an electron-donating substance and a
substance with a high electron-transport property, a layer formed
of a transparent conductive film, or the like can be used. As for a
light-emitting element having such a structure, problems such as
energy transfer and quenching hardly occur, and a light-emitting
element which has both high emission efficiency and a long lifetime
can be easily obtained due to expansion in the choice of materials.
Moreover, a light-emitting element which provides phosphorescence
from one of the EL layers and fluorescence from the other of the EL
layers can be readily obtained. Note that this structure can be
combined with the above-described structures of the EL layer.
[0163] Similarly, a light-emitting element in which three or more
EL layers 802 are stacked as illustrated in FIG. 2B can also be
employed. A plurality of EL layers with a charge-generation layer
interposed therebetween is provided between a pair of electrodes,
as in the light-emitting element according to this embodiment,
whereby it is possible to realize an element having a long lifetime
which can emit light at a high luminance while current density is
kept low.
[0164] As illustrated in FIG. 1C, the EL layer may include the
hole-injection layer 701, the hole-transport layer 702, the
light-emitting layer 703, the electron-transport layer 704, an
electron-injection buffer layer 706, an electron-relay layer 707,
and a composite material layer 708 which is in contact with the
second electrode 108, between the first electrode 101 and the
second electrode 108.
[0165] It is preferable to provide the composite material layer 708
which is in contact with the second electrode 108, in which case
damage caused to the EL layer 102 particularly when the second
electrode 108 is formed by a sputtering method can be reduced. The
composite material layer 708 can be formed using the composite
material of one embodiment of the present invention.
[0166] Further, by providing the electron-injection buffer layer
706, an injection barrier between the composite material layer 708
and the electron-transport layer 704 can be reduced; thus,
electrons generated in the composite material layer 708 can be
easily injected to the electron-transport layer 704.
[0167] A substance having a high electron-injection property, such
as an alkali metal, an alkaline earth metal, a rare earth metal, a
compound of the above metal (e.g., an alkali metal compound (e.g.,
an oxide such as lithium oxide, a halide, and a carbonate such as
lithium carbonate or cesium carbonate), an alkaline earth metal
compound (e.g., an oxide, a halide, and a carbonate), or a rare
earth metal compound (e.g., an oxide, a halide, and a carbonate),
can be used for the electron-injection buffer layer 706.
[0168] Further, in the case where the electron-injection buffer
layer 706 contains a substance having a high electron-transport
property and a donor substance, the donor substance is preferably
added so that the mass ratio of the donor substance to the
substance having a high electron-transport property ranges from
0.001:1 to 0.1:1. Note that as the donor substance, an organic
compound such as tetrathianaphthacene (abbreviation: TTN),
nickelocene, or decamethylnickelocene can be used as well as an
alkali metal, an alkaline earth metal, a rare earth metal, a
compound of the above metal (e.g., an alkali metal compound
(including an oxide of lithium oxide or the like, a halide, and a
carbonate such as lithium carbonate or cesium carbonate), an
alkaline earth metal compound (including an oxide, a halide, and a
carbonate), and a rare earth metal compound (including an oxide, a
halide, and a carbonate). Note that as the substance having a high
electron-transport property, a material similar to the material for
the electron-transport layer 704 described above can be used.
[0169] Furthermore, it is preferable that the electron-relay layer
707 be formed between the electron-injection buffer layer 706 and
the composite material layer 708. The electron-relay layer 707 is
not necessarily provided; however, by providing the electron-relay
layer 707 having a high electron-transport property, electrons can
be rapidly transported to the electron-injection buffer layer
706.
[0170] The structure in which the electron-relay layer 707 is
sandwiched between the composite material layer 708 and the
electron-injection buffer layer 706 is a structure in which the
acceptor substance contained in the composite material layer 708
and the donor substance contained in the electron-injection buffer
layer 706 are less likely to interact with each other, and thus
their functions hardly interfere with each other. Therefore, an
increase in drive voltage can be suppressed.
[0171] The electron-relay layer 707 contains a substance having a
high electron-transport property and is formed so that the LUMO
level of the substance having a high electron-transport property is
located between the LUMO level of the acceptor substance contained
in the composite material layer 708 and the LUMO level of the
substance having a high electron-transport property contained in
the electron-transport layer 704. In the case where the
electron-relay layer 707 contains a donor substance, the donor
level of the donor substance is controlled so as to be located
between the LUMO level of the acceptor substance contained in the
composite material layer 708 and the LUMO level of the substance
having a high electron-transport property contained in the
electron-transport layer 704. As a specific value of the energy
level, the LUMO level of the substance having a high
electron-transport property contained in the electron-relay layer
707 is preferably higher than or equal to -5.0 eV, more preferably
higher than or equal to -5.0 eV and lower than or equal to -3.0
eV.
[0172] As the substance having a high electron-transport property
contained in the electron-relay layer 707, a phthalocyanine-based
material or a metal complex having a metal-oxygen bond and an
aromatic ligand is preferably used.
[0173] As the phthalocyanine-based material contained in the
electron-relay layer 707, for example, any of CuPc, a
phthalocyanine tin(II) complex (SnPc), a phthalocyanine zinc
complex (ZnPc), cobalt(II) phthalocyanine, .beta.-form (CoPc),
phthalocyanine iron (FePc), and vanadyl
2,9,16,23-tetraphenoxy-29H,31H-phthalocyanine (PhO-VOPc), is
preferably used.
[0174] As the metal complex having a metal-oxygen bond and an
aromatic ligand, which is contained in the electron-relay layer
707, a metal complex having a metal-oxygen double bond is
preferably used. The metal-oxygen double bond has an acceptor
property (a property of easily accepting electrons); thus,
electrons can be transferred (donated and accepted) more easily.
Further, the metal complex having a metal-oxygen double bond is
considered stable. Thus, the use of the metal complex having the
metal-oxygen double bond enables the light-emitting element to be
driven more stably at low voltage.
[0175] As the metal complex having a metal-oxygen bond and an
aromatic ligand, a phthalocyanine-based material is preferable.
Specifically, any of vanadyl phthalocyanine (VOPc), a
phthalocyanine tin(IV) oxide complex (SnOPc), and a phthalocyanine
titanium oxide complex (TiOPc) is preferable because a metal-oxygen
double bond is likely to act on another molecular in tenns of a
molecular structure and an acceptor property is high.
[0176] Note that as the phthalocyanine-based materials described
above, a phthalocyanine-based material having a phenoxy group is
preferable. Specifically, a phthalocyanine derivative having a
phenoxy group, such as PhO-VOPc, is preferable. The phthalocyanine
derivative having a phenoxy group is soluble in a solvent; thus,
the phthalocyanine derivative has an advantage of being easily
handled during formation of a light-emitting element and an
advantage of facilitating maintenance of an apparatus used for film
formation.
[0177] The electron-relay layer 707 may further contain a donor
substance. As the donor substance, an organic compound such as
tetrathianaphthacene (abbreviation: TTN), nickelocene, or
decamethylnickelocene can be used as well as an alkali metal, an
alkaline earth metal, a rare earth metal, and a compound of the
above metal (e.g., an alkali metal compound (including an oxide
such as lithium oxide, a halide, and a carbonate such as lithium
carbonate or cesium carbonate), an alkaline earth metal compound
(including an oxide, a halide, and a carbonate), and a rare earth
metal compound (including an oxide, a halide, and a carbonate)).
When such a donor substance is contained in the electron-relay
layer 707, electrons can be transferred easily and the
light-emitting element can be driven at lower voltage.
[0178] In the case where a donor substance is contained in the
electron-relay layer 707, other than the materials described above
as the substance having a high electron-transport property, a
substance having a LUMO level higher than the acceptor level of the
acceptor substance contained in the composite material layer 708
can be used. Specifically, it is preferable to use a substance
having a LUMO level higher than or equal to -5.0 eV, preferably
higher than or equal to -5.0 eV and lower than or equal to -3.0 eV.
As examples of such a substance, a perylene derivative, a
nitrogen-containing condensed aromatic compound, and the like are
given. Note that a nitrogen-containing condensed aromatic compound
is preferably used for the electron-relay layer 707 because of its
stability.
[0179] Specific examples of the perylene derivative are
3,4,9,10-perylenetetracarboxylic dianhydride (abbreviation: PTCDA),
3,4,9, 10-perylenetetracarboxylic-b is-b enzimidazole
(abbreviation: PTCBI),
N,N'-dioctyl-3,4,9,10-perylenetetracarboxylic diimide
(abbreviation: PTCDI-C8H),
N,N'-dihexyl-3,4,9,10-perylenetetracarboxylic diimide
(abbreviation: Hex PTC), and the like.
[0180] Specific examples of the nitrogen-containing condensed
aromatic compound are pirazino
[2,3-f][1,10]phenanthroline-2,3-dicarbonitrile (abbreviation:
PPDN), 2,3,6,7,10,11-hexacyano-1,4,5,8,9,12-hexaazatriphenylene
(abbreviation: HAT(CN).sub.6), 2,3-diphenylpyrido[2,3-b]pyrazine
(abbreviation: 2PYPR), 2,3-bis(4-fluorophenyl)pyrido[2,3-b]pyrazine
(abbreviation: F2PYPR), and the like.
[0181] Besides, 7,7,8, 8-tetracyanoquino d imethane (abbreviation:
TCNQ), 1,4,5,8-naphthalenetetracarboxylic dianhydride
(abbreviation: NTCDA), perfluoropentacene, copper
hexadecafluorophthalocyanine (abbreviation: F.sub.16CuPc),
N,N'-bis(2,2,3,3,4,4,5,5,6,6,7,7,8,8,8-pentadecafluorooctyl-1,4,5,8-napht-
halenetetracarboxylic diimide (abbreviation: NTCDI-C8F),
3',4'-dibutyl-5,5''-bis(dicyanomethylene)-5,5''-dihydro-2,2':5',2''-terth-
iophen (abbreviation: DCMT), methanofullerene (e.g., [6,6]-phenyl
C.sub.61 butyric acid methyl ester), or the like can be used.
[0182] Note that in the case where a donor substance is contained
in the electron-relay layer 707, the electron-relay layer 707 may
be formed by a method such as co-evaporation of the substance
having a high electron-transport property and the donor
substance.
[0183] The hole-injection layer 701, the hole-transport layer 702,
the light-emitting layer 703, and the electron-transport layer 704
may each be formed using any of the above-described materials.
[0184] Note that this embodiment can be implemented in appropriate
combination with any of the other embodiments.
Embodiment 3
[0185] In this embodiment, a light-emitting device including a
light-emitting element of one embodiment of the present invention
will be described with reference to FIGS. 3A and 3B. Note that FIG.
3A is a top view illustrating the light-emitting device, and FIG.
3B is a cross-sectional view taken along lines A-B and C-D of FIG.
3A.
[0186] In FIG. 3A, reference numeral 401 denotes a driver circuit
portion (a source side driver circuit), reference numeral 402
denotes a pixel portion, and reference numeral 403 denotes a driver
circuit portion (a gate side driver circuit), which are each
indicated by dotted lines. Reference numeral 404 denotes a sealing
substrate, reference numeral 405 denotes a sealing material, and a
portion enclosed by the sealing material 405 is a space 407.
[0187] Note that a lead wiring 408 is a wiring for transmitting
signals that are to be input to the source side driver circuit 401
and the gate side driver circuit 403, and receives a video signal,
a clock signal, a start signal, a reset signal, and the like from a
flexible printed circuit (FPC) 409 which serves as an external
input terminal. Although only the FPC is illustrated here, a
printed wiring board (PWB) may be attached to the FPC. The
light-emitting device in this specification includes not only a
light-emitting device itself but also a light-emitting device to
which an FPC or a PWB is attached.
[0188] Next, a cross-sectional structure will be described with
reference to FIG. 3B. The driver circuit portion and the pixel
portion are formed over an element substrate 410. Here, the source
side driver circuit 401 which is the driver circuit portion and one
pixel in the pixel portion 402 are illustrated.
[0189] Note that as the source side driver circuit 401, a CMOS
circuit which includes an n-channel TFT 423 and a p-channel TFT 424
is formed. The driver circuit may be any of a variety of circuits
formed with TFTs, such as a CMOS circuit, a PMOS circuit, or an
NMOS circuit. Although a driver-integrated type in which a driver
circuit is formed over the substrate is described in this
embodiment, the present invention is not limited to this type, and
the driver circuit can be formed outside the substrate.
[0190] The pixel portion 402 includes a plurality of pixels having
a switching TFT 411, a current control TFT 412, and a first
electrode 413 electrically connected to a drain of the current
control TFT 412. Note that an insulator 414 is formed to cover an
end portion of the first electrode 413. Here, the insulator 414 is
formed by using a positive type photosensitive acrylic resin
film.
[0191] In order to improve coverage, the insulator 414 is provided
such that either an upper end portion or a lower end portion of the
insulator 414 has a curved surface with a curvature. For example,
when positive photosensitive acrylic is used as a material for the
insulator 414, it is preferable that only an upper end portion of
the insulator 414 have a curved surface with a radius of curvature
(0.2 .mu.m to 3 .mu.m). For the insulator 414, it is also possible
to use either a negative type that becomes insoluble in an etchant
by light irradiation or a positive type that becomes soluble in an
etchant by light irradiation.
[0192] An EL layer 416 and a second electrode 417 are formed over
the first electrode 413. Here, as a material for forming the first
electrode 413 functioning as the anode, a material having a high
work function is preferably used. For example, it is possible to
use a single layer of an ITO film, an indium tin oxide film that
includes silicon, an indium oxide film that includes 2 wt % to 20
wt % of zinc oxide, a titanium nitride film, a chromium film, a
tungsten film, a Zn film, a Pt film, or the like, a stacked layer
of a titanium nitride film and a film that mainly includes
aluminum, a three-layer structure of a titanium nitride film, a
film that mainly includes aluminum, and a titanium nitride film, or
the like. Note that, when a stacked layer structure is employed,
resistance of a wiring is low and an excellent ohmic contact is
obtained.
[0193] In addition, the EL layer 416 is formed by any of various
methods such as an evaporation method using an evaporation mask, a
droplet discharging method like an inkjet method, a printing
method, and a spin coating method. The EL layer 416 includes the
composite material described in Embodiment 1. Further, another
material included in the EL layer 416 may be a low molecular
material, an oligomer, a dendrimer, a high molecular material, or
the like.
[0194] As a material used for the second electrode 417 which is
formed over the EL layer 416 and serves as a cathode, it is
preferable to use a material having a low work function (e.g., Al,
Mg, Li, Ca, or an alloy or a compound thereof such as Mg--Ag,
Mg--In, or Al--Li). In order that light generated in the EL layer
416 be transmitted through the second electrode 417, a stack of a
metal thin film having a reduced thickness and a transparent
conductive film (e.g., ITO, indium oxide containing 2 wt % to 20 wt
% of zinc oxide, indium oxide-tin oxide that includes silicon or
silicon oxide, or zinc oxide) is preferably used for the second
electrode 417.
[0195] Further, the sealing substrate 404 is attached to the
element substrate 410 with the sealing material 405, so that a
light-emitting element 418 is provided in the space 407 enclosed by
the element substrate 410, the sealing substrate 404, and the
sealing material 405. The space 407 is filled with a filler, and
may be filled with an inert gas (such as nitrogen or argon) or the
sealing material 405.
[0196] Note that an epoxy-based resin is preferably used as the
sealing material 405. Such a material preferably allows as little
moisture and oxygen as possible to penetrate. As a material used
for the sealing substrate 404, a plastic substrate formed of
fiberglass-reinforced plastics (FRP), polyvinyl fluoride (PVF),
polyester, acrylic, or the like can be used other than a glass
substrate or a quartz substrate.
[0197] As described above, the active matrix light-emitting device
including the light-emitting element of one embodiment of the
present invention can be obtained.
[0198] Further, a light-emitting element of the present invention
can be used for a passive matrix light-emitting device as well as
the above active matrix light-emitting device. FIGS. 4A and 4B
illustrate a perspective view and a cross-sectional view of a
passive matrix light-emitting device including a light-emitting
element of the present invention. Note that FIG. 4A is a
perspective view of the light-emitting device, and FIG. 4B is a
cross-sectional view taken along line X-Y of FIG. 4A.
[0199] In FIGS. 4A and 4B, an EL layer 504 is provided between a
first electrode 502 and a second electrode 503 over a substrate
501. An end portion of the first electrode 502 is covered with an
insulating layer 505. In addition, a partition layer 506 is
provided over the insulating layer 505. The sidewalls of the
partition layer 506 slope so that a distance between both the
sidewalls is gradually narrowed toward the surface of the
substrate. In other words, a cross section taken along the
direction of the short side of the partition layer 506 is
trapezoidal, and the base (side in contact with the insulating
layer 505) is shorter than the upper side (side not in contact with
the insulating layer 505). With the partition layer 506 provided in
such a way, a defect of a light-emitting element due to crosstalk
or the like can be prevented.
[0200] Thus, the passive matrix light-emitting device including a
light-emitting element of one embodiment of the present invention
can be obtained.
[0201] The light-emitting devices described in this embodiment (the
active matrix light-emitting device and the passive matrix
light-emitting device) are both formed using a light-emitting
element of one embodiment of the present invention, and
accordingly, the light-emitting devices have low power
consumption.
[0202] Note that this embodiment can be implemented in appropriate
combination with any of the other embodiments.
Embodiment 4
[0203] In this embodiment, with reference to FIGS. 5A to 5E and
FIG. 6, description is given of examples of a variety of electronic
devices and lighting devices that are each completed by using a
light-emitting device which is one embodiment of the present
invention.
[0204] Examples of the electronic devices to which the
light-emitting device is applied are television devices (also
referred to as TV or television receivers), monitors for computers
and the like, cameras such as digital cameras and digital video
cameras, digital photo frames, cellular phones (also referred to as
portable telephone devices), portable game machines, portable
information terminals, audio playback devices, large game machines
such as pin-ball machines, and the like. Specific examples of these
electronic devices and a lighting device are illustrated in FIGS.
5A to 5E.
[0205] FIG. 5A illustrates an example of a television device. In
the television device 7100, a display portion 7103 is incorporated
in a housing 7101. The display portion 7103 is capable of
displaying images, and a light-emitting device can be used for the
display portion 7103. In addition, here, the housing 7101 is
supported by a stand 7105.
[0206] The television device 7100 can be operated with an operation
switch of the housing 7101 or a separate remote controller 7110.
With operation keys 7109 of the remote controller 7110, channels
and volume can be controlled and images displayed on the display
portion 7103 can be controlled. Furthermore, the remote controller
7110 may be provided with a display portion 7107 for displaying
data output from the remote controller 7110.
[0207] Note that the television device 7100 is provided with a
receiver, a modem, and the like. With the receiver, general
television broadcasting can be received. Furthermore, when the
television device 7100 is connected to a communication network by
wired or wireless connection via the modem, one-way (from a
transmitter to a receiver) or two-way (between a transmitter and a
receiver, between receivers, or the like) data communication can be
performed.
[0208] FIG. 5B illustrates a computer, which includes a main body
7201, a housing 7202, a display portion 7203, a keyboard 7204, an
external connection port 7205, a pointing device 7206, and the
like. This computer is manufactured by using a light-emitting
device for the display portion 7203.
[0209] FIG. 5C illustrates a portable game machine, which includes
two housings, a housing 7301 and a housing 7302, connected with a
joint portion 7303 so that the portable game machine can be opened
or closed. A display portion 7304 is incorporated in the housing
7301 and a display portion 7305 is incorporated in the housing
7302. In addition, the portable game machine illustrated in FIG. 5C
includes a speaker portion 7306, a recording medium insertion
portion 7307, an LED lamp 7308, an input means (an operation key
7309, a connection terminal 7310, a sensor 7311 (a sensor having a
function of measuring force, displacement, position, speed,
acceleration, angular velocity, rotational frequency, distance,
light, liquid, magnetism, temperature, chemical substance, sound,
time, hardness, electric field, current, voltage, electric power,
radiation, flow rate, humidity, gradient, oscillation, odor, or
infrared rays), and a microphone 7312), and the like. It is
needless to say that the structure of the portable game machine is
not limited to the above as long as a light-emitting device is used
for at least either the display portion 7304 or the display portion
7305, or both, and may include other accessories as appropriate.
The portable game machine illustrated in FIG. 5C has a function of
reading out a program or data stored in a storage medium to display
it on the display portion, and a function of sharing information
with another portable game machine by wireless communication. The
portable game machine illustrated in FIG. 5C can have a variety of
functions without limitation to the above.
[0210] FIG. 5D illustrates an example of a cellular phone. The
cellular phone 7400 is provided with a display portion 7402
incorporated in a housing 7401, operation buttons 7403, an external
connection port 7404, a speaker 7405, a microphone 7406, and the
like. Note that the cellular phone 7400 is manufactured using a
light-emitting device for the display portion 7402.
[0211] When the display portion 7402 of the cellular phone 7400
illustrated in FIG. 5D is touched with a finger or the like, data
can be input to the cellular phone 7400. Further, operations such
as making a call and creating e-mail can be performed by touch on
the display portion 7402 with a finger or the like.
[0212] There are mainly three screen modes of the display portion
7402. The first mode is a display mode mainly for displaying an
image. The second mode is an input mode mainly for inputting
information such as characters. The third mode is a
display-and-input mode in which two modes of the display mode and
the input mode are mixed.
[0213] For example, in the case of making a call or creating
e-mail, a character input mode mainly for inputting characters is
selected for the display portion 7402 so that characters displayed
on a screen can be input. In this case, it is preferable to display
a keyboard or number buttons on almost the entire screen of the
display portion 7402.
[0214] When a detection device including a sensor for detecting
inclination, such as a gyroscope or an acceleration sensor, is
provided inside the cellular phone 7400, display on the screen of
the display portion 7402 can be automatically changed by
determining the orientation of the cellular phone 7400 (whether the
cellular phone is placed horizontally or vertically for a landscape
mode or a portrait mode).
[0215] The screen modes are switched by touch on the display
portion 7402 or operation with the operation buttons 7403 of the
housing 7401. Alternatively, the screen modes can be switched
depending on kinds of images displayed on the display portion 7402.
For example, when a signal for an image to be displayed on the
display portion is data of moving images, the screen mode is
switched to the display mode. When the signal is text data, the
screen mode is switched to the input mode.
[0216] Moreover, in the input mode, if a signal detected by an
optical sensor in the display portion 7402 is detected and the
input by touch on the display portion 7402 is not performed during
a certain period, the screen mode may be controlled so as to be
switched from the input mode to the display mode.
[0217] The display portion 7402 may function as an image sensor.
For example, an image of a palm print, a fingerprint, or the like
is taken by touch on the display portion 7402 with the palm or the
finger, whereby personal identification can be performed.
Furthermore, by provision of a backlight or a sensing light source
emitting near-infrared light for the display portion, an image of a
finger vein, a palm vein, or the like can also be taken.
[0218] FIG. 5E illustrates a desk lamp, which includes a lighting
portion 7501, a shade 7502, an adjustable arm 7503, a support 7504,
a base 7505, and a power switch 7506. The desk lamp is manufactured
using a light-emitting device for the lighting portion 7501. Note
that the "lighting device" also includes ceiling lights, wall
lights, and the like.
[0219] FIG. 6 illustrates an example in which a light-emitting
device is used for an interior lighting device 811. Since the
light-emitting device can have a larger area, it can be used as a
lighting device having a large area. Furthermore, the
light-emitting device can be used as a roll-type lighting device
812. As illustrated in FIG. 6, a desk lamp 813 described with
reference to FIG. 5E may also be used in a room provided with the
interior lighting device 811.
[0220] In the above-described manner, electronic devices or
lighting devices can be obtained by application of a light-emitting
device. Application range of the light-emitting device is so wide
that the light-emitting device can be applied to electronic devices
in a variety of fields.
[0221] Note that the structure described in this embodiment can be
combined with any of the structures described in Embodiments 1 to 3
as appropriate.
EXAMPLE 1
[0222] In this example, specific examples of the composite material
of one embodiment of the present invention will be described. The
composite material of one embodiment of the present invention
includes a heterocyclic compound having a dibenzothiophene skeleton
or a dibenzofuran skeleton and an inorganic compound exhibiting an
electron-accepting property with respect to the heterocyclic
compound. Table 1 shows heterocyclic compounds used in Composition
Examples 1 to 9 of this example and the HOMO levels of the
heterocyclic compounds (measured by photoelectron spectrometry). In
addition, structural formulae of the heterocyclic compounds are
illustrated below.
TABLE-US-00001 TABLE 1 heterocyclic compound HOMO level Composition
Example 1 DBTFLP-IV -6.0 Composition Example 2 DBT3P-II -6.0
Composition Example 3 oDBTBP-II -5.9 Composition Example 4
DBTFLP-III -5.9 Composition Example 5 mDBTPTp-II -5.9 Composition
Example 6 DBT2PC-II -5.7 Composition Example 7 2mDBTPPA-II -5.7
Composition Example 8 2mDBFPPA-II -5.7 Composition Example 9
mDBTPA-II -5.7
##STR00005## ##STR00006## ##STR00007##
[0223] In each of Composition Examples 1 to 9, molybdenum oxide was
used as the inorganic compound.
[0224] A method for preparing the composite material of one
embodiment of the present invention will be described using
Composition Example 1 as an example. Composition Examples 2 to 9
were prepared in a manner similar to that of Composition Example 1;
thus, the description thereof is omitted.
COMPOSITION EXAMPLE 1
[0225] First, a glass substrate was fixed to a substrate holder
inside a vacuum evaporation apparatus. Then,
4-[4-(9-phenyl-9H-fluoren-9-yl)phenyl]-6-phenyldibenzothiophene
(abbreviation: DBTFLP-IV) and molybdenum(VI) oxide were separately
put in respective resistance-heating evaporation sources, and in a
vacuum state, films containing DBTFLP-IV and molybdenum oxide were
formed by a co-evaporation method. At this time, DBTFLP-IV and
molybdenum(VI) oxide were co-evaporated such that the mass ratios
of DBTFLP-IV to molybdenum(VI) oxide were 4:2, 4:1, and 4:0.5
(=DBTFLP-IV:molybdenum oxide). Further, the thickness of each film
was set to 50 nm.
[0226] FIGS. 7A and 7B show results of measurement of absorption
spectra of the thus formed composite films of DBTFLP-IV and
molybdenum oxide (Composition Example 1). In addition, for
comparison, an absorption spectrum of a film of only DBTFLP-IV (50
nm thick) is also shown. Note that as for Composition Examples 2 to
9, an absorption spectrum of a film of only the heterocyclic
compound used in each composition example is also shown for
comparison.
[0227] Similarly, FIGS. 8A and 8B show results of measurement of
absorption spectra of composite films of
1,3,5-tri(dibenzothiophen-4-yl)-benzene (abbreviation: DBT3P-II)
and molybdenum oxide (Composition Example 2). Note that the
thickness of each film was set to 50 nm.
[0228] FIGS. 9A and 9B show results of measurement of absorption
spectra of composite films of
4,4'-(biphenyl-2,2'-diyl)-bis-dibenzothiophene (abbreviation:
oDBTBP-II) and molybdenum oxide (Composition Example 3). Note that
the thickness of only a film of oDBTBP-II and molybdenum(VI) oxide
at a mass ratio of 4:1 (=oDBTBP-II:molybdenum oxide) was 47 nm. The
thickness of the other films was set to 50 nm.
[0229] FIGS. 10A and 10B show results of measurement of absorption
spectra of composite films of
2,8-diphenyl-4-[4-(9-phenyl-9H-fluoren-9-yl)phenyl]dibenzothiophene
(abbreviation: DBTFLP-III) and molybdenum oxide (Composition
Example 4). Note that the thickness of each film was set to 50
nm.
[0230] FIGS. 11A and 11B show results of measurement of absorption
spectra of composite films of
4-[3-(triphenylen-2-yl)phenyl]dibenzothiophene (abbreviation:
mDBTPTp-II) and molybdenum oxide (Composition Example 5). Note that
the thickness of each film was set to 50 nm.
[0231] FIGS. 12A and 12B show results of measurement of absorption
spectra of composite films of
3,6-di-(dibenzothiophen-4-yl)-9-phenyl-9H-carbazole (abbreviation:
DBT2PC-II) and molybdenum oxide (Composition Example 6). Note that
the thickness of each film was set to 50 nm.
[0232] FIGS. 13A and 13B show results of measurement of absorption
spectra of composite films of
4-[3-(9,10-diphenyl-2-anthryl)phenyl]dibenzothiophene
(abbreviation: 2mDBTPPA-II) and molybdenum oxide (Composition
Example 7). Note that the thickness of each film was set to 50
nm.
[0233] FIGS. 14A and 14B show results of measurement of absorption
spectra of composite films of
4-[3-(9,10-diphenyl-2-anthryl)phenyl]dibenzofuran (abbreviation:
2mDBFPPA-II) and molybdenum oxide (Composition Example 8). Note
that the thickness of each film was set to 50 nm.
[0234] FIGS. 15A and 15B show results of measurement of absorption
spectra of composite films of
4-[4-(9-phenylanthracen-10-yl)phenyl]dibenzothiophene
(abbreviation: mDBTPA-II) and molybdenum oxide (Composition Example
9). Note that the thickness of each film was set to 50 nm.
[0235] In each of FIGS. 7A to 15B, the horizontal axis represents
wavelength (nm) and the vertical axis represents absorptance (no
unit).
[0236] FIGS. 7A to 15B show that the composite materials of one
embodiment of the present invention given in Composition Examples 1
to 9 are materials that have almost no significant absorption peak
in the visible light region and have a high light-transmitting
property. Composition Examples 7 to 9 each have an anthracene
skeleton. When the composite material of one embodiment of the
present invention includes a heterocyclic compound having an
anthracene skeleton, a tetracene skeleton, a perylene skeleton, or
the like and the thickness thereof is large, a slight absorption
peak originating from the skeleton is observed in the visible light
region. On the other hand, it is found that Composition Examples 1
to 6 are materials that have no significant absorption peak in a
region of wavelengths of 360 nm and more and have a particularly
high light-transmitting property.
[0237] The composite materials of one embodiment of the present
invention given in Composition Examples 1 to 9 have almost no
significant absorption peak also in the infrared region (a region
of wavelengths of 700 nm and more).
[0238] The absorption spectrum of the composite material of one
embodiment of the present invention including the heterocyclic
compound and molybdenum oxide has substantially the same shape as
the absorption spectrum of the heterocyclic compound. A film having
a high concentration of molybdenum oxide (specifically, the film of
the heterocyclic compound and molybdenum oxide at a mass ratio of
4:2 of each composition example) also has almost no significant
absorption peak in a range from the visible light region to the
infrared region. This indicates that in the composite material of
one embodiment of the present invention, light absorption due to
charge transfer interaction is unlikely to occur.
EXAMPLE 2
[0239] In this example, a light-emitting element of one embodiment
of the present invention will be described with reference to FIG.
16A. Structural formulae of materials used in this example are
illustrated below.
##STR00008## ##STR00009## ##STR00010##
[0240] Methods for manufacturing Light-Emitting Element 1,
Comparative Light-Emitting Element 2, and Comparative
Light-Emitting Element 3 of this example will be described
below.
(Light-Emitting Element 1)
[0241] First, a film of indium tin oxide containing silicon oxide
(ITSO) was formed over a glass substrate 1100 by a sputtering
method, so that a first electrode 1101 which functions as an anode
was formed. Note that the thickness was set to 110 nm and the
electrode area was set to 2 mm.times.2 mm.
[0242] Next, in pretreatment for forming the light-emitting element
over the substrate 1100, UV ozone treatment was performed for 370
seconds after washing of a surface of the substrate with water and
baking that was performed at 200.degree. C. for one hour.
[0243] After that, the substrate was transferred into a vacuum
evaporation apparatus where the pressure had been reduced to
approximately 10.sup.-4 Pa, and was subjected to vacuum baking at
170.degree. C. for 30 minutes in a heating chamber of the vacuum
evaporation apparatus, and then the substrate 1100 was cooled down
for about 30 minutes.
[0244] Next, the substrate 1100 provided with the first electrode
1101 was fixed to a substrate holder in the vacuum evaporation
apparatus so that a surface on which the first electrode 1101 was
provided faced downward. The pressure in the vacuum evaporation
apparatus was reduced to about 10.sup.-4 Pa. Then,
4-[4-(9-phenyl-9H-fluoren-9-yl)phenyl]-6-phenyldibenzothiophene
(abbreviation: DBTFLP-IV) and molybdenum(VI) oxide were
co-evaporated to form a hole-injection layer 1111 over the first
electrode 1101. The thickness of the hole-injection layer 1111 was
set to 50 nm, and the mass ratio of DBTFLP-IV to molybdenum(VI)
oxide was adjusted to 4:2 (=DBTFLP-IV:molybdenum oxide). Note that
the co-evaporation method refers to an evaporation method in which
evaporation is carried out from a plurality of evaporation sources
at the same time in one treatment chamber.
[0245] Next, over the hole-injection layer 1111, a film of
3-[4-(9-phenanthryl)-phenyl1-9-phenyl-9H-carbazole (abbreviation:
PCPPn) was formed to a thickness of 10 nm to form a hole-transport
layer 1112.
[0246] Furthermore, 9-[4-(N-carbazolyl)]phenyl-10-phenylanthracene
(abbreviation: CzPA) and
N,N'-bis[4-(9-phenyl-9H-fluoren-9-yl)phenyl]-N,N'-diphenylpyrene-1,6-diam-
ine (abbreviation: 1,6FLPAPrn) were co-evaporated to form a
light-emitting layer 1113 over the hole-transport layer 1112. Here,
the mass ratio of CzPA to 1,6FLPAPrn was adjusted to 1:0.05
(=CzPA:1,6FLPAPrn). In addition, the thickness of the
light-emitting layer 1113 was set to 30 nm.
[0247] Further, over the light-emitting layer 1113, a film of CzPA
was formed to a thickness of 10 nm to form a first
electron-transport layer 1114a.
[0248] Then, over the first electron-transport layer 1114a, a film
of bathophenanthroline (abbreviation: BPhen) was formed to a
thickness of 15 nm to form a second electron-transport layer
1114b.
[0249] Further, over the second electron-transport layer 1114b, a
film of lithium fluoride (LiF) was formed by evaporation to a
thickness of 1 nm to form an electron-injection layer 1115.
[0250] Lastly, an aluminum film was formed by evaporation to a
thickness of 200 nm as a second electrode 1103 functioning as a
cathode. Thus, Light-Emitting Element 1 of this example was
fabricated.
[0251] Note that, in all the above evaporation steps, evaporation
was performed by a resistance-heating method.
(Comparative Light-Emitting Element 2)
[0252] A hole-injection layer 1111 of Comparative Light-Emitting
Element 2 was formed by co-evaporating
9-phenyl-3-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazole
(abbreviation: PCzPA) and molybdenum(VI) oxide. The thickness of
the hole-injection layer 1111 was set to 50 nm, and the mass ratio
of PCzPA to molybdenum(VI) oxide was adjusted to 4:2
(=PCzPA:molybdenum oxide). Components other than the hole-injection
layer 1111 were manufactured in a manner similar to that of
Light-Emitting Element 1.
(Comparative Light-Emitting Element 3)
[0253] A hole-injection layer 1111 of Comparative Light-Emitting
Element 3 was formed by co-evaporating
4-phenyl-4'-(9-phenylfluoren-9-yl)triphenylamine (abbreviation:
BPAFLP) and molybdenum(VI) oxide. The thickness of the
hole-injection layer 1111 was set to 50 nm, and the mass ratio of
BPAFLP to molybdenum(VI) oxide was adjusted to 4:2
(=BPAFLP:molybdenum oxide). Components other than the
hole-injection layer 1111 were manufactured in a manner similar to
that of Light-Emitting Element 1.
[0254] Table 2 shows element structures of Light-Emitting Element
1, Comparative Light-Emitting Element 2, and Comparative
Light-Emitting Element 3 obtained as described above.
TABLE-US-00002 TABLE 2 first hole- hole- light- electrode injection
layer transport layer emitting layer Light-Emitting ITSO
DBTFLP-IV:MoOx PCPPn CzPA:1,6FLPAPrn Element 1 110 nm (=4:2) 10 nm
(=1:0.05) 50 nm 30 nm Comparative ITSO PCzPA:MoOx PCPPn
CzPA:1,6FLPAPrn Light-Emitting 110 nm (=4:2) 10 nm (=1:0.05)
Element 2 50 nm 30 nm Comparative ITSO BPAFLP:MoOx PCPPn
CzPA:1,6FLPAPrn Light-Emitting 110 nm (=4:2) 10 nm (=1:0.05)
Element 3 50 nm 30 nm first electron- second electron- electron-
second transport layer transport layer injection layer electrode
Light-Emitting CzPA BPhen LiF Al Element 1 10 nm 15 nm 1 nm 200 nm
Comparative CzPA BPhen LiF Al Light-Emitting 10 nm 15 nm 1 nm 200
nm Element 2 Comparative CzPA BPhen LiF Al Light-Emitting 10 nm 15
nm 1 nm 200 nm Element 3
[0255] In a glove box containing a nitrogen atmosphere, these
light-emitting elements were sealed so as not to be exposed to air.
Then, operation characteristics of these light-emitting elements
were measured. Note that the measurements were carried out at room
temperature (in the atmosphere kept at 25.degree. C.).
[0256] Note that the above-described three light-emitting elements
were formed over the same substrate. In addition, the first
electrodes and the hole-transport layers to the second electrodes
of the above-described three light-emitting elements were formed at
the same respective times, and sealing was performed at the same
time.
[0257] FIG. 17 shows the voltage-luminance characteristics of
Light-Emitting Element 1, Comparative Light-Emitting Element 2, and
Comparative Light-Emitting Element 3. In FIG. 17, the horizontal
axis represents voltage (V) and the vertical axis represents
luminance (cd/m.sup.2). FIG. 18 shows the luminance-current
efficiency characteristics. In FIG. 18, the horizontal axis
represents luminance (cd/m.sup.2) and the vertical axis represents
current efficiency (cd/A). Further, Table 3 shows the voltage (V),
CIE chromaticity coordinates (x, y), current efficiency (cd/A), and
external quantum efficiency (%) of each light-emitting element at a
luminance of 1000 cd/m.sup.2.
TABLE-US-00003 TABLE 3 CIE external chromaticity current quantum
voltage coordinates efficiency efficiency (V) (x, y) (cd/A) (%)
Light-Emitting 3.1 (0.15, 0.23) 12 7.9 Element 1 Comparative 3.0
(0.15, 0.22) 11 7.1 Light-Emitting Element 2 Comparative 3.4 (0.15,
0.22) 8.4 5.7 Light-Emitting Element 3
[0258] As shown in Table 3, the CIE chromaticity coordinates of
Light-Emitting Element 1 were (x, y)=(0.15, 0.23), the CLE
chromaticity coordinates of Comparative Light-Emitting Element 2
were (x, y)=(0.15, 0.22), and the CIE chromaticity coordinates of
Comparative Light-Emitting Element 3 were (x, y)=(0.15, 0.22), each
at a luminance of around 1000 cd/m.sup.2. These results show that
blue light emission originating from 1,6FLPAPrn was obtained from
Light-Emitting Element 1, Comparative Light-Emitting Element 2, and
Comparative Light-Emitting Element 3.
[0259] As can be seen from FIG. 17, at the same voltage,
Light-Emitting Element 1 has a luminance higher than that of
Comparative Light-Emitting Element 3 and comparable to that of
Comparative Light-Emitting Element 2. In addition, as can be seen
from FIG. 18 and Table 3, Light-Emitting Element 1 has a current
efficiency and external quantum efficiency higher than those of
Comparative Light-Emitting Element 2 and Comparative Light-Emitting
Element 3.
[0260] Next, Light-Emitting Element 1, Comparative Light-Emitting
Element 2, and Comparative Light-Emitting Element 3 were subjected
to reliability tests. Results of the reliability tests are shown in
FIG. 19. In FIG. 19, the vertical axis represents normalized
luminance (%) with an initial luminance of 100%, and the horizontal
axis represents driving time (h) of the element.
[0261] In the reliability tests, the light-emitting elements of
this example were driven under the conditions where the initial
luminance was set to 5000 cd/m.sup.2 and the current density was
constant.
[0262] FIG. 19 shows that Light-Emitting Element 1 kept 54% of the
initial luminance after 260 hours elapsed. On the other hand, the
luminance of Comparative Light-Emitting Element 2 after 200 hours
was 50% or less of the initial luminance. In addition, the
luminance of Comparative Light-Emitting Element 3 after 62 hours
was 50% or less of the initial luminance.
[0263] It is found that Light-Emitting Element 1 according to one
embodiment of the present invention has a longer lifetime than
Comparative Light-Emitting Element 2 and Comparative Light-Emitting
Element 3.
[0264] The above results suggest that an element having high
emission efficiency can be realized by use of the composite
material of one embodiment of the present invention for a
hole-injection layer of the light-emitting element. The results
also suggest that a light-emitting element having a low drive
voltage can be provided by use of the composite material of one
embodiment of the present invention for a hole-injection layer of
the light-emitting element. The results also suggest that a
light-emitting element having a long lifetime can be manufactured
by use of the composite material of one embodiment of the present
invention for a hole-injection layer.
EXAMPLE 3
[0265] In this example, a light-emitting element of one embodiment
of the present invention will be described with reference to FIG.
16A. A structural formula of a material used in this example is
illustrated below. Note that the structural formulae of materials
which are already illustrated will be omitted.
##STR00011##
[0266] A method for manufacturing Light-Emitting Element 4 of this
example will be described below.
(Light-Emitting Element 4)
[0267] A hole-injection layer 1111 of Light-Emitting Element 4 was
formed by co-evaporating 1,3,5-tri(dibenzothiophen-4-yl)-benzene
(abbreviation: DBT3P-II) and molybdenum(VI) oxide. The thickness of
the hole-injection layer 1111 was set to 50 nm, and the mass ratio
of DBT3P-II to molybdenum(VI) oxide was adjusted to 4:2
(=DBT3P-II:molybdenum oxide). Components other than the
hole-injection layer 1111 were manufactured in a manner similar to
that of Light-Emitting Element 1 described in Example 2.
[0268] Table 4 shows an element structure of Light-Emitting Element
4 obtained as described above.
TABLE-US-00004 TABLE 4 first hole- hole- light- electrode injection
layer transport layer emitting layer Light-Emitting ITSO
DBT3P-II:MoOx PCPPn CzPA:1,6FLPAPrn Element 4 110 nm (=4:2) 10 nm
(=1:0.05) 50 nm 30 nm first electron- second electron- electron-
second transport layer transport layer injection layer electrode
Light-Emitting CzPA BPhen LiF Al Element 4 10 nm 15 nm 1 nm 200
nm
[0269] In a glove box containing a nitrogen atmosphere,
Light-Emitting Element 4 was sealed so as not to be exposed to air.
Then, operation characteristics of Light-Emitting Element 4 were
measured. Note that the measurements were carried out at room
temperature (in the atmosphere kept at 25.degree. C.).
[0270] FIG. 20 shows the voltage-luminance characteristics of
Light-Emitting Element 4. In FIG. 20, the horizontal axis
represents voltage (V) and the vertical axis represents luminance
(cd/m.sup.2). FIG. 21 shows the luminance-current efficiency
characteristics. In FIG. 21, the horizontal axis represents
luminance (cd/m.sup.2) and the vertical axis represents current
efficiency (cd/A). Further, Table 5 shows the voltage (V), CIE
chromaticity coordinates (x, y), current efficiency (cd/A), and
external quantum efficiency (%) of Light-Emitting Element 4 at a
luminance of 1000 cd/m.sup.2.
TABLE-US-00005 TABLE 5 CIE external chromaticity current quantum
voltage coordinates efficiency efficiency (V) (x, y) (cd/A) (%)
Light-Emitting 3.0 (0.15, 0.22) 11 7.4 Element 4
[0271] As shown in Table 5, the CIE chromaticity coordinates of
Light-Emitting Element 4 were (x, y)=(0.15, 0.22) at a luminance of
1000 cd/m.sup.2. These results show that blue light emission
originating from 1,6FLPAPrn was obtained from Light-Emitting
Element 4.
[0272] As can be seen from FIG. 20, FIG. 21, and Table 5,
Light-Emitting Element 4 exhibits high emission efficiency. It can
also be seen that Light-Emitting Element 4 is a light-emitting
element having a low drive voltage.
[0273] Next, Light-Emitting Element 4 was subjected to a
reliability test. Results of the reliability test are shown in FIG.
22. In FIG. 22, the vertical axis represents normalized luminance
(%) with an initial luminance of 100%, and the horizontal axis
represents driving time (h) of the element.
[0274] In the reliability test, the light-emitting element of this
example was driven under the conditions where the initial luminance
was set to 5000 cd/m.sup.2 and the current density was
constant.
[0275] FIG. 22 shows that Light-Emitting Element 4 kept 55% of the
initial luminance after 310 hours elapsed.
[0276] The above results suggest that a light-emitting element
having high emission efficiency can be realized by use of the
composite material of one embodiment of the present invention. The
results also suggest that a light-emitting element having a low
drive voltage can be manufactured by use of the composite material
of one embodiment of the present invention. The results also
suggest that a light-emitting element having a long lifetime can be
provided by use of the composite material of one embodiment of the
present invention.
EXAMPLE 4
[0277] In this example, a light-emitting element of one embodiment
of the present invention will be described with reference to FIG.
16A. A structural fotinula of a material used in this example is
illustrated below. Note that the structural formulae of materials
which are already illustrated will be omitted.
##STR00012##
[0278] A method for manufacturing Light-Emitting Element 5 of this
example will be described below.
(Light-Emitting Element 5)
[0279] A hole-injection layer 1111 of Light-Emitting Element 5 was
formed by co-evaporating
2,8-diphenyl-4-[4-(9-phenyl-9H-fluoren-9-yl)phenyl]dibenzothiophene
(abbreviation: DBTFLP-III) and molybdenum(VI) oxide. The thickness
of the hole-injection layer 1111 was set to 50 nm, and the mass
ratio of DBTFLP-III to molybdenum(VI) oxide was adjusted to 4:2
(=DBTFLP-III:molybdenum oxide). Components other than the
hole-injection layer 1111 were manufactured in a manner similar to
that of Light-Emitting Element 1 described in Example 2.
[0280] Table 6 shows an element structure of Light-Emitting Element
5 obtained as described above.
TABLE-US-00006 TABLE 6 first hole- hole- light- electrode injection
layer transport layer emitting layer Light-Emitting ITSO
DBTFLP-III:MoOx PCPPn CzPA:1,6FLPAPrn Element 5 110 nm (=4:2) 10 nm
(=1:0.05) 50 nm 30 nm first electron- second electron- electron-
second transport layer transport layer injection layer electrode
Light-Emitting CzPA BPhen LiF Al Element 5 10 nm 15 nm 1 nm 200
nm
[0281] In a glove box containing a nitrogen atmosphere,
Light-Emitting Element 5 was sealed so as not to be exposed to air.
Then, operation characteristics of Light-Emitting Element 5 were
measured. Note that the measurements were carried out at room
temperature (in the atmosphere kept at 25.degree. C.).
[0282] FIG. 23 shows the voltage-luminance characteristics of
Light-Emitting Element 5. In FIG. 23, the horizontal axis
represents voltage (V) and the vertical axis represents luminance
(cd/m.sup.2). FIG. 24 shows the luminance-current efficiency
characteristics. In FIG. 24, the horizontal axis represents
luminance (cd/m.sup.2) and the vertical axis represents current
efficiency (cd/A). Further, Table 7 shows the voltage (V), CIE
chromaticity coordinates (x, y), current efficiency (cd/A), and
external quantum efficiency (%) of Light-Emitting Element 5 at a
luminance of 1000 cd/m.sup.2.
TABLE-US-00007 TABLE 7 CIE external chromaticity current quantum
voltage coordinates efficiency efficiency (V) (x, y) (cd/A) (%)
Light-Emitting 3.0 (0.15, 0.23) 11 7.5 Element 5
[0283] As shown in Table 7, the CIF chromaticity coordinates of
Light-Emitting Element 5 were (x, y)=(0.15, 0.23) at a luminance of
1000 cd/m.sup.2. These results show that blue light emission
originating from 1,6FLPAPrn was obtained from Light-Emitting
Element 5.
[0284] As can be seen from FIG. 23, FIG. 24, and Table 7,
Light-Emitting Element 5 exhibits high emission efficiency. It can
also be seen that Light-Emitting Element 5 is a light-emitting
element having a low drive voltage.
[0285] The above results suggest that a light-emitting element
having high emission efficiency can be realized by use of the
composite material of one embodiment of the present invention. The
results also suggest that a light-emitting element having a low
drive voltage can be manufactured by use of the composite material
of one embodiment of the present invention.
EXAMPLE 5
[0286] In this example, specific examples of the composite material
of one embodiment of the present invention will be described. The
composite material of one embodiment of the present invention,
includes a heterocyclic compound having a dibenzothiophene skeleton
or a dibenzofuran skeleton and an inorganic compound exhibiting an
electron-accepting property with respect to the heterocyclic
compound. Table 8 shows heterocyclic compounds used in Composition
Examples 10 to 14 of this example and the HOMO levels of the
heterocyclic compounds used in Composition Examples 10 to 13
(measured by photoelectron spectrometry). In addition, structural
formulae of the heterocyclic compounds used in this example are
illustrated below.
TABLE-US-00008 TABLE 8 heterocyclic compound HOMO level Composition
Example 10 DBTPPC-II -5.7 Composition Example 11 mDBTPPC-II -5.6
Composition Example 12 DBTPPn-II -5.9 Composition Example 13
mmDBFFLBi-II -5.9 Composition Example 14 mZ-DBT2-II
##STR00013## ##STR00014##
[0287] In each of Composition Examples 10 to 14, molybdenum oxide
was used as the inorganic compound.
[0288] A method for preparing the composite material of one
embodiment of the present invention will be described using
Composition Example 10 as an example. Composition Examples 11 to 14
were prepared in a manner similar to that of Composition Example
10; thus, the description thereof is omitted.
COMPOSITION EXAMPLE 10
[0289] First, a glass substrate was fixed to a substrate holder
inside a vacuum evaporation apparatus. Then,
3-[4-(dibenzothiophen-4-yl)-phenyl]-9-phenyl-9H-carbazole
(abbreviation: DBTPPC-II) and molybdenum(VI) oxide were separately
put in respective resistance-heating evaporation sources, and in a
vacuum state, films containing DBTPPC-II and molybdenum oxide were
formed by a co-evaporation method. At this time, DBTPPC-II and
molybdenum(VI) oxide were co-evaporated such that the mass ratios
of DBTPPC-II to molybdenum(VI) oxide were 4:2, 4:1, and 4:0.5
(=DBTPPC-II:molybdenum oxide). Further, the thickness of each film
was set to 50 nm.
[0290] FIGS. 25A and 25B show results of measurement of absorption
spectra of the thus formed composite films of DBTPPC-II and
molybdenum oxide (Composition Example 10). In addition, for
comparison, an absorption spectrum of a film of only DBTPPC-II (50
nm thick) is also shown. Note that as for Composition Examples 11,
12, and 14, an absorption spectrum of a film of only the
heterocyclic compound used in each composition example is also
shown for comparison.
[0291] Similarly, FIGS. 26A and 26B show results of measurement of
absorption spectra of composite films of
3-[3-(dibenzothiophen-4-yl)-phenyl]-9-phenyl-9H-carbazole
(abbreviation: mDBTPPC-II) and molybdenum oxide (Composition
Example 11). Note that the thickness of each film was set to 50
nm.
[0292] FIGS. 27A and 27B show results of measurement of an
absorption spectrum of a composite film of
4-[4-(9-phenanthryl)phenyl]dibenzothiophene (abbreviation:
DBTPPn-II) and molybdenum oxide (Composition Example 12). Note that
the composite film given in Composition Example 12 is only a film
of DBTPPn-II and molybdenum(VI) oxide at a mass ratio of 4:2
(=DBTPPn-II:molybdenum oxide). The thickness of each of the
composite film and the film of only DB IPPn-II was set to 50
nm.
[0293] FIGS. 28A and 28B show results of measurement of an
absorption spectrum of a composite film of
4,4'-{(1,1':2',1'':2'',1'')-quaterphenyl-3,3'''-yl}bisdibenzothiophene
(abbreviation: mZ-DBT2-II) and molybdenum oxide (Composition
Example 13). Note that only a film of mZ-DBT2-II and molybdenum
oxide at a mass ratio of 4:2 (=mZ-DBT2-II:molybdenum oxide) is
shown for Composition Example 13 (the thickness: 50 nm).
[0294] FIGS. 29A and 29B show results of measurement of absorption
spectra of composite films of
4-{3-[3-(9-phenyl-9H-fluoren-9-yl)phenyl]phenyl}dibenzofuran
(abbreviation: mmDBFFLBi-II) and molybdenum oxide (Composition
Example 14). Note that the thickness of each film was set to 50
nm.
[0295] In each of FIGS. 25A to 29B, the horizontal axis represents
wavelength (nm) and the vertical axis represents absorptance (no
unit).
[0296] FIGS. 25A to 29B show that the composite materials of one
embodiment of the present invention given in Composition Examples
10 to 14 are materials that have almost no significant absorption
peak in the visible light region and have a high light-transmitting
property. The composite materials of one embodiment of the present
invention given in Composition Examples 10 to 14 have almost no
significant absorption peak also in the infrared region (a region
of wavelengths of 700 nm and more).
[0297] The absorption spectrum of the composite material of one
embodiment of the present invention including the heterocyclic
compound and molybdenum oxide has substantially the same shape as
the absorption spectrum of the heterocyclic compound. A film having
a high concentration of molybdenum oxide (specifically, the film of
the heterocyclic compound and molybdenum oxide at a mass ratio of
4:2 of each composition example) also has almost no significant
peak in a range from the visible light region to the infrared
region. This indicates that in the composite material of one
embodiment of the present invention, light absorption due to charge
transfer interaction is unlikely to occur.
EXAMPLE 6
[0298] In this example, a light-emitting element of one embodiment
of the present invention will be described with reference to FIG.
16A. Structural formulae of materials used in this example are
illustrated below. Note that the structural formulae of materials
which are already illustrated will be omitted.
##STR00015##
[0299] A method for manufacturing Light-Emitting Element 6 of this
example will be described below.
(Light-Emitting Element 6)
[0300] First, in a manner similar to that of Light-Emitting Element
1 described in Example 2, a film of ITSO was formed over a glass
substrate 1100 to form a first electrode 1101.
[0301] Next, the substrate 1100 provided with the first electrode
1101 was fixed to a substrate holder in the vacuum evaporation
apparatus so that a surface on which the first electrode 1101 was
provided faced downward. The pressure in the vacuum evaporation
apparatus was reduced to about 10.sup.-4 Pa. Then,
4,4'-{(1,1':2',1'':2'',1''')-quaterphenyl-3,3'''-yl}bisdibenzothiophene
(abbreviation: mZ-DBT2-II) and molybdenum(VI) oxide were
co-evaporated to form a hole-injection layer 1111 over the first
electrode 1101. The thickness of the hole-injection layer 1111 was
set to 50 nm, and the mass ratio of mZ-DBT2-II to molybdenum(VI)
oxide was adjusted to 4:2 mZ-DBT2-II:molybdenum oxide).
[0302] Next, over the hole-injection layer 1111, a film of
3-[4-(1-naphthyl)-phenyl]-9-phenyl-9H-carbazole (abbreviation:
PCPN) was formed to a thickness of 10 nm to form a hole-transport
layer 1112.
[0303] Furthermore, CzPA and
N,N'-bis(3-methylphenyl)-N,N'-bis[3-(9-phenyl-9H-fluoren-9-yl)phenyl]-pyr-
ene-1,6-diamine (abbreviation: 1,6mMemFLPAPrn) were co-evaporated
to form a light-emitting layer 1113 over the hole-transport layer
1112. Here, the mass ratio of CzPA to 1,6mMemFLPAPrn was adjusted
to 1:0.04 (=CzPA:1,6mMemFLPAPrn). In addition, the thickness of the
light-emitting layer 1113 was set to 30 nm.
[0304] Further, over the light-emitting layer 1113, a film of CzPA
was formed to a thickness of 10 nm to form a first
electron-transport layer 1114a.
[0305] Then, over the first electron-transport layer 1114a, a BPhen
film was formed to a thickness of 15 nm to form a second
electron-transport layer 1114b.
[0306] Further, over the second electron-transport layer 1114b, a
LiF film was formed by evaporation to a thickness of 1 nm to form
an electron-injection layer 1115.
[0307] Lastly, an aluminum film was formed by evaporation to a
thickness of 200 nm as a second electrode 1103 functioning as a
cathode. Thus, Light-Emitting Element 6 of this example was
fabricated.
[0308] Note that, in all the above evaporation steps, evaporation
was performed by a resistance-heating method.
[0309] Table 9 shows an element structure of Light-Emitting Element
6 obtained as described above.
TABLE-US-00009 TABLE 9 first hole- hole- light- electrode injection
layer transport layer emitting layer Light-Emitting ITSO
mZ-DBT2-II:MoOx PCPN CzPA:1,6mMemFLPAPrn Element 6 110 nm (=4:2) 10
nm (=1:0.04) 50 nm 30 nm first electron- second electron- electron-
second transport layer transport layer injection layer electrode
Light-Emitting CzPA BPhen LiF Al Element 6 10 nm 15 nm 1 nm 200
nm
[0310] In a glove box containing a nitrogen atmosphere,
Light-Emitting Element 6 was sealed so as not to be exposed to air.
Then, operation characteristics of Light-Emitting Element 6 were
measured. Note that the measurements were carried out at room
temperature (in the atmosphere kept at 25.degree. C.).
[0311] FIG. 30 shows the voltage-luminance characteristics of
Light-Emitting Element 6. In FIG. 30, the horizontal axis
represents voltage (V) and the vertical axis represents luminance
(cd/m.sup.2). FIG. 31 shows the luminance-current efficiency
characteristics. In FIG. 31, the horizontal axis represents
luminance (cd/m.sup.2) and the vertical axis represents current
efficiency (cd/A). Further, Table 10 shows the voltage (V), CIE
chromaticity coordinates (x, y), current efficiency (cd/A), and
external quantum efficiency (%) of Light-Emitting Element 6 at a
luminance of 1000 cd/m.sup.2.
TABLE-US-00010 TABLE 10 CIE external chromaticity current quantum
voltage coordinates efficiency efficiency (V) (x, y) (cd/A) (%)
Light-Emitting 3.1 (0.14, 0.16) 10 8.8 Element 6
[0312] As shown in Table 10, the CIE chromaticity coordinates of
Light-Emitting Element 6 were (x, y)=(0.14, 0.16) at a luminance of
1000 cd/m.sup.2. These results show that blue light emission
originating from 1,6mMemFLPAPrn was obtained from Light-Emitting
Element 6.
[0313] As can be seen from FIG. 30, FIG. 31, and Table 10,
Light-Emitting Element 6 exhibits high emission efficiency. It can
also be seen that Light-Emitting Element 6 is a light-emitting
element having a low drive voltage.
[0314] Next, Light-Emitting Element 6 was subjected to a
reliability test. Results of the reliability test are shown in FIG.
32. In FIG. 32, the vertical axis represents normalized luminance
(%) with an initial luminance of 100%, and the horizontal axis
represents driving time (h) of the element.
[0315] In the reliability test, Light-Emitting Element 6 was driven
under the conditions where the initial luminance was set to 5000
cd/m.sup.2 and the current density was constant.
[0316] FIG. 32 shows that Light-Emitting Element 6 kept 54% of the
initial luminance after 280 hours elapsed.
[0317] The above results suggest that an element having high
emission efficiency can be realized by use of the composite
material of one embodiment of the present invention for a
hole-injection layer of the light-emitting element. The results
also suggest that a light-emitting element having a low drive
voltage can be provided by use of the composite material of one
embodiment of the present invention for a hole-injection layer of
the light-emitting element. The results also suggest that a
light-emitting element having a long lifetime can be manufactured
by use of the composite material of one embodiment of the present
invention for a hole-injection layer.
EXAMPLE 7
[0318] In this example, a light-emitting element of one embodiment
of the present invention will be described with reference to FIG.
16A. A structural formula of a material used in this example is
illustrated below. Note that the structural formulae of materials
which are already illustrated will be omitted.
##STR00016##
[0319] A method for manufacturing Light-Emitting Element 7 of this
example will be described below.
(Light-Emitting Element 7)
[0320] A hole-injection layer 1111 of Light-Emitting Element 7 was
formed by co-evaporating
4-{3-[3-(9-phenyl-9H-fluoren-9-yl)phenyl]phenyl}dibenzofuran
(abbreviation: mmDBFFLBi-II) and molybdenum(VI) oxide. The
thickness of the hole-injection layer 1111 was set to 50 nm, and
the mass ratio of mmDBFFLBi-II to molybdenum(VI) oxide was adjusted
to 4:2 (=mmDBFFLBi-II:molybdenum oxide).
[0321] A hole-transport layer 1112 of Light-Emitting Element 7 was
foimed by forming a film of mmDBFFLBi-II to a thickness of 10 nm.
Components other than the hole-injection layer 1111 and the
hole-transport layer 1112 were manufactured in a manner similar to
that of Light-Emitting Element 6 described in Example 6.
[0322] Table 11 shows an element structure of Light-Emitting
Element 7 obtained as described above.
TABLE-US-00011 TABLE 11 first hole- hole- light- electrode
injection layer transport layer emitting layer Light-Emitting ITSO
mmDBFFLBi-II:MoOx mmDBFFLBi-II CzPA:1,6mMemFLPAPrn Element 7 110 nm
(=4:2) 10 nm (=1:0.04) 50 nm 30 nm first electron- second electron-
electron- second transport layer transport layer injection layer
electrode Light-Emitting CzPA BPhen LiF Al Element 7 10 nm 15 nm 1
nm 200 nm
[0323] In a glove box containing a nitrogen atmosphere,
Light-Emitting Element 7 was sealed so as not to be exposed to air.
Then, operation characteristics of Light-Emitting Element 7 were
measured. Note that the measurements were carried out at room
temperature (in the atmosphere kept at 25.degree. C.).
[0324] FIG. 33 shows the voltage-luminance characteristics of
Light-Emitting Element 7. In FIG. 33, the horizontal axis
represents voltage (V) and the vertical axis represents luminance
(cd/m.sup.2). FIG. 34 shows the luminance-current efficiency
characteristics. In FIG. 34, the horizontal axis represents
luminance (cd/m.sup.2) and the vertical axis represents current
efficiency (cd/A). Further, Table 12 shows the voltage (V), CIE
chromaticity coordinates (x, y), current efficiency (cd/A), and
external quantum efficiency (%) of Light-Emitting Element 7 at a
luminance of 1000 cd/m.sup.2.
TABLE-US-00012 TABLE 12 CIE external chromaticity current quantum
voltage coordinates efficiency efficiency (V) (x, y) (cd/A) (%)
Light-Emitting 3.1 (0.14, 0.16) 10 8.8 Element 7
[0325] As shown in Table 12, the CIE chromaticity coordinates of
Light-Emitting Element 7 were (x, y)=(0.14, 0.16) at a luminance of
1000 cd/m.sup.2. These results show that blue light emission
originating from 1,6mMemELPAPrn was obtained from Light-Emitting
Element 7.
[0326] As can be seen from FIG. 32, FIG. 33, and Table 12,
Light-Emitting Element 7 exhibits high emission efficiency. It can
also be seen that Light-Emitting Element 7 is a light-emitting
element haying a low drive voltage.
[0327] The above results suggest that an element having high
emission efficiency can be realized by use of the composite
material of one embodiment of the present invention for a
hole-injection layer of the light-emitting element. The results
also suggest that a light-emitting element having a low drive
voltage can be provided by use of the composite material of one
embodiment of the present invention for a hole-injection layer of
the light-emitting element.
EXAMPLE 8
[0328] In this example, a light-emitting element of one embodiment
of the present invention will be described with reference to FIG.
16A. The materials used in this example are used in the above
examples, and therefore the chemical formulae thereof are omitted
here.
[0329] A method for manufacturing Light-Emitting Element 8 of this
example will be described below.
(Light-Emitting Element 8)
[0330] A hole-injection layer 1111 of Light-Emitting Element 8 was
formed by co-evaporating mmDBFFLBi-II and molybdenum(VI) oxide. The
thickness of the hole-injection layer 1111 was set to 50 nm, and
the mass ratio of mmDBFFLBi-II to molybdenum(VI) oxide was adjusted
to 4:2 mmDBFFLBi-II:molybdenum oxide).
[0331] The hole-transport layer 1112 of Light-Emitting Element 8
was formed by forming a film of PCzPA to a thickness of 10 nm.
Components other than the hole-injection layer 1111 and the
hole-transport layer 1112 were manufactured in a manner similar to
that of Light-Emitting Element 6 described in Example 6.
[0332] Table 13 shows an element structure of Light-Emitting
Element 8 obtained as described above.
TABLE-US-00013 TABLE 13 first hole- hole- light- electrode
injection layer transport layer emitting layer Light-Emitting ITSO
mmDBFFLBi-II:MoOx PCzPA CzPA:1,6mMemFLPAPrn Element 8 110 nm (=4:2)
10 nm (=1:0.04) 50 nm 30 nm first electron- second electron-
electron- second transport layer transport layer injection layer
electrode Light-Emitting CzPA BPhen LiF Al Element 8 10 nm 15 nm 1
nm 200 nm
[0333] In a glove box containing a nitrogen atmosphere,
Light-Emitting Element 8 was sealed so as not to be exposed to air.
Then, operation characteristics of Light-Emitting Element 8 were
measured. Note that the measurements were carried out at room
temperature (in the atmosphere kept at 25.degree. C.).
[0334] FIG. 35 shows the voltage-luminance characteristics of
Light-Emitting Element 8. In FIG. 35, the horizontal axis
represents voltage (V) and the vertical axis represents luminance
(cd/m.sup.2). FIG. 36 shows the luminance-current efficiency
characteristics. In FIG. 36, the horizontal axis represents
luminance (cd/m.sup.2) and the vertical axis represents current
efficiency (cd/A). Further, Table 14 shows the voltage (V), CIE
chromaticity coordinates (x, y), current efficiency (cd/A), and
external quantum efficiency (%) of Light-Emitting Element 8 at a
luminance of 1000 cd/m.sup.2.
TABLE-US-00014 TABLE 14 CIE external chromaticity current quantum
voltage coordinates efficiency efficiency (V) (x, y) (cd/A) (%)
Light-Emitting 3.2 (0.14, 0.18) 8.8 6.8 Element 8
[0335] As shown in Table 14, the CIF chromaticity coordinates of
Light-Emitting Element 8 were (x, y)=(0.14, 0.18) at a luminance of
1000 cd/m.sup.2. These results show that blue light emission
originating from 1,6mMemFLPAPrn was obtained from Light-Emitting
Element 8.
[0336] As can be seen from FIG. 34, FIG. 35, and Table 14,
Light-Emitting Element 8 exhibits high emission efficiency. It can
also be seen that Light-Emitting Element 8 is a light-emitting
element having a low drive voltage.
[0337] The above results suggest that an element having high
emission efficiency can be realized by use of the composite
material of one embodiment of the present invention for a
hole-injection layer of the light-emitting element. The results
also suggest that a light-emitting element having a low drive
voltage can be provided by use of the composite material of one
embodiment of the present invention for a hole-injection layer of
the light-emitting element.
EXAMPLE 9
[0338] In this example, a light-emitting element of one embodiment
of the present invention will be described with reference to FIG.
16B. A structural formula of a material used in this example is
illustrated below. Note that structural formulae of the materials
used in the above examples are omitted here.
##STR00017##
[0339] Methods for manufacturing Light-Emitting Element 9 and
Comparative Light-Emitting Element 10 of this example will be
described below.
(Light-Emitting Element 9)
[0340] First, an ITSO film was formed over a glass substrate 1100
by a sputtering method, so that a first electrode 1101 which
functions as an anode was formed. Note that the thickness was set
to 110 nm and the electrode area was set to 2 mm.times.2 mm.
[0341] In pretreatment for forming the light-emitting element over
the substrate 1100, UV ozone treatment was performed for 370
seconds after washing of a surface of the substrate with water and
baking that was performed at 200.degree. C. for one hour.
[0342] After that, the substrate was transferred into a vacuum
evaporation apparatus where the pressure had been reduced to
approximately 10.sup.-4 Pa, and was subjected to vacuum baking at
170.degree. C. for 30 minutes in a heating chamber of the vacuum
evaporation apparatus, and then the substrate 1100 was cooled down
for about 30 minutes.
[0343] Next, the substrate 1100 provided with the first electrode
1101 was fixed to a substrate holder in the vacuum evaporation
apparatus so that a surface on which the first electrode 1101 was
provided faced downward. The pressure in the vacuum evaporation
apparatus was reduced to about 10.sup.-4 Pa. Then, DBT3P-II and
molybdenum(VI) oxide were co-evaporated to form a first
hole-injection layer 1111a over the first electrode 1101. The
thickness of the first hole-injection layer 1111a was set to 50 nm,
and the mass ratio of DBT3P-II to molybdenum(VI) oxide was adjusted
to 4:2 (=DBT3P-11:molybdenum oxide).
[0344] Next, over the first hole-injection layer 1111a, a film of
PCPN was formed to a thickness of 10 nm to form a first
hole-transport layer 1112a.
[0345] Next, CzPA and 1,6FLPAPrn were co-evaporated to form a first
light-emitting layer 1113a over the first hole transport-layer
1112a. Here, the mass ratio of CzPA to 1,6FLPAPrn was adjusted to
1:0.05 (=CzPA:1,6FLPAPrn). The thickness of the first
light-emitting layer 1113a was set to 30 nm.
[0346] Next, over the first light-emitting layer 1113a, a CzPA film
was formed to a thickness of 10 nm and a BPhen film was formed to a
thickness of 15 nm to form a first electron-transport layer
1114a.
[0347] Further, over the first electron-transport layer 1114a, a
film of lithium oxide (Li.sub.2O) was folined by evaporation to a
thickness of 0.1 nm to form a first electron-injection layer
1115a.
[0348] After that, over the first electron-injection layer 1115a, a
film of copper phthalocyanine (abbreviation: CuPc) was formed by
evaporation to a thickness of 2 nm to form an electron-relay layer
1116.
[0349] Next, over the electron-relay layer 1116, DBT3P-II and
molybdenum(VI) oxide were co-evaporated to form a second
hole-injection layer 1111b. The thickness of the second
hole-injection layer 1111b was set to 50 nm, and the mass ratio of
DBT3P-II to molybdenum(VI) oxide was adjusted to 4:2
DBT3P-II:molybdenum oxide). Note that the second hole-injection
layer 1111b of this example functions as the charge-generation
layer described in the above embodiment.
[0350] Next, over the second hole-injection layer 1111b, a PCPN
film was formed to a thickness of 10 nm to form a second
hole-transport layer 1112b.
[0351] Furthermore, CzPA and 1,6FLPAPrn were co-evaporated to form
a second light-emitting layer 1113b over the second hole-transport
layer 1112b. Here, the mass ratio of CzPA to 1,6FLPAPrn was
adjusted to 1:0.05 (=CzPA:1,6FLPAPrn). In addition, the thickness
of the second light-emitting layer 1113b was set to 30 nm.
[0352] Further, over the second light-emitting layer 1113b, a film
of CzPA was formed to a thickness of 10 nm and a film of BPhen was
formed to a thickness of 15 nm to fonn a second electron-transport
layer 1114b.
[0353] Further, over the second electron-transport layer 1114b, a
film of LiF was formed to a thickness of 1 nm to form a second
electron-injection layer 1115b.
[0354] Lastly, an aluminum film was formed by evaporation to a
thickness of 200 nm as a second electrode 1103 functioning as a
cathode. Thus, Light-Emitting Element 9 of this example was
fabricated.
(Comparative Light-Emitting Element 10)
[0355] A first hole-injection layer 1111a of Comparative
Light-Emitting Element 10 was formed by co-evaporating PCzPA and
molybdenum(VI) oxide. The thickness of the first hole-injection
layer 1111a was set to 50 nm, and the mass ratio of PCzPA to
molybdenum(VI) oxide was adjusted to 4:2 (=PCzPA: molybdenum
oxide).
[0356] A second hole-injection layer 1111b of Comparative
Light-Emitting Element 10 was formed by co-evaporating PCzPA and
molybdenum(VI) oxide. The thickness of the second hole-injection
layer 1111b was set to 60 nm, and the mass ratio of PCzPA to
molybdenum(VI) oxide was adjusted to 4:2 (=PCzPA:molybdenum oxide).
Components other than the first hole-injection layer 1111a and the
second hole-injection layer 1111b were manufactured in a manner
similar to that of Light-Emitting Element 9.
[0357] Note that, in all the above evaporation steps, evaporation
was performed by a resistance-heating method.
[0358] Table 15 shows element structures of Light-Emitting Element
9 and Comparative Light-Emitting Element 10 obtained as described
above. Note that as for Light-Emitting Element 9, the substance X
in Table 15 is DBT3P-II and the thickness Y is 50 nm. In addition,
as for Comparative Light-Emitting Element 10, the substance X in
Table 15 is PCzPA and the thickness Y is 60 nm.
TABLE-US-00015 TABLE 15 first electrode ITSO 110 nm first first
first first hole- first electron- electron- hole-injection
transport light-emitting transport injection electron-relay layer
layer layer layer layer layer substance X:MoOx PCPN CzPA:
1,6FLPAPrn CzPA Bphen Li.sub.2O CuPc (=4:2) 10 nm (=1:0.05) 10 nm
15 nm 0.1 nm 2 nm 50 nm 30 nm second second second second hole-
second electron- electron- hole-injection transport light-emitting
transport injection second layer layer layer layer layer electrode
substance X:MoOx PCPN CzPA:1,6FLPAPrn CzPA Bphen LiF Al (=4:2) 10
nm (=1:0.05) 10 nm 15 nm 1 nm 200 nm thickness Y 30 nm
[0359] In a glove box containing a nitrogen atmosphere, these
light-emitting elements were sealed so as not to be exposed to air.
Then, operation characteristics of these light-emitting elements
were measured. Note that the measurements were carried out at room
temperature (in the atmosphere kept at 25.degree. C.).
[0360] Note that the above-described two light-emitting elements
were formed over the same substrate. In addition, the first
electrodes, the first hole-transport layers to the electron-relay
layers, and the second hole-transport layers to the second
electrodes of the above-described two light-emitting elements were
formed at the same respective times, and sealing was performed at
the same time.
[0361] FIG. 37 shows the voltage-luminance characteristics of
Light-Emitting Element 9 and Comparative Light-Emitting Element 10.
In FIG. 37, the horizontal axis represents voltage (V) and the
vertical axis represents luminance (cd/m.sup.2). FIG. 38 shows the
luminance-current efficiency characteristics. In FIG. 38, the
horizontal axis represents luminance (cd/m.sup.2) and the vertical
axis represents current efficiency (cd/A). Further, Table 16 shows
the voltage (V), CIE chromaticity coordinates (x, y), current
efficiency (cd/A), power efficiency (lm/W), and external quantum
efficiency (%) of Light-Emitting Element 9 and Comparative
Light-Emitting Element 10 at a luminance of 1000 cd/m.sup.2.
TABLE-US-00016 TABLE 16 CIE current power external chromaticity
effi- effi- quantum voltage coordinates ciency ciency efficiency
(V) (x, y) (cd/A) (lm/W) (%) Light-Emitting 6.0 (0.14, 0.20) 23 12
16 Element 9 Comparative 6.0 (0.14, 0.20) 21 11 15 Light-Emitting
Element 10
[0362] As shown in Table 16, the CIE chromaticity coordinates of
each of Light-Emitting Element 9 and Comparative Light-Emitting
Element 10 were (x, y)=(0.14, 0.20) at a luminance of 1000
cd/m.sup.2.
[0363] As can be seen from FIG. 38 and Table 16, Light-Emitting
Element 9 has current efficiency, power efficiency, and external
quantum efficiency higher than those of Comparative Light-Emitting
Element 10.
[0364] Here, an absorption spectrum of the composite material
including PCzPA and molybdenum oxide used in Comparative
Light-Emitting Element 10 was measured and compared with that of
the composite material including DBT3P-II and molybdenum oxide
(FIGS. 8A and 8B) used in Light-Emitting Element 9.
[0365] FIGS. 39A and 39B show absorption spectra of films formed by
co-evaporating PCzPA and molybdenum(VI) oxide (at mass ratios of
4:2, 4:1, and 4:0.5 (=PCzPA:molybdenum oxide)) to a thickness of 50
nm. Note that in FIGS. 39A and 39B, the horizontal axis represents
wavelength (nm) and the vertical axis represents absorptance (no
unit).
[0366] As shown in FIGS. 39A and 39B, the composite material
including PCzPA and molybdenum oxide has an absorption peak in the
visible light region. On the other hand, as described in Example 1,
the composite material including DBT3P-II and molybdenum oxide has
almost no significant absorption peak in the visible light region
(FIGS. 8A and 8B).
[0367] This indicates that the composite material including
DBT3P-II and molybdenum oxide has a higher transmittance in the
visible light region than the composite material including PCzPA
and molybdenum oxide and therefore Light-Emitting Element 9 has
current efficiency higher than that of Comparative Light-Emitting
Element 10.
[0368] The above results suggest that an element having high
emission efficiency can be realized by use of the composite
material of one embodiment of the present invention for a
hole-injection layer and a charge-generation layer of a tandem
light-emitting element. The results also suggest that a
light-emitting element having a low drive voltage can be provided
by use of the composite material of one embodiment of the present
invention for a hole-injection layer and a charge-generation layer
of a tandem light-emitting element. The results also show that the
composite material of one embodiment of the present invention
functions quite effectively as a charge-generation layer of a
tandem light-emitting element despite the fact that no light
absorption due to charge transfer interaction is observed.
EXAMPLE 10
[0369] In this example, results of evaluation of the composite
material of one embodiment of the present invention by an electron
spin resonance (ESR) method will be described. In this example, the
composite material of one embodiment of the present invention which
includes DBT3P-II and molybdenum oxide is compared with a
conventional composite material which includes
4,4'-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (abbreviation: NPB)
and molybdenum oxide. A structural formula of NPB is illustrated
below.
##STR00018##
(Comparison Between Absorption Spectra of Composite Materials)
[0370] First, an absorption spectrum of the conventional composite
material which includes NPB and molybdenum oxide was measured and
compared with that of the composite material of one embodiment of
the present invention which includes DBT3P-II and molybdenum oxide
(FIGS. 8A and 8B).
[0371] FIGS. 40A and 40B show absorption spectra of films formed by
co-evaporating NPB and molybdenum(VI) oxide (at mass ratios of 4:2,
4:1, and 4:0.5 (=NPB:molybdenum oxide)) to a thickness of 50 nm.
Note that in FIGS. 40A and 40B, the horizontal axis represents
wavelength (nm) and the vertical axis represents absorptance (no
unit).
[0372] A comparison between FIGS. 40A and 40B and FIGS. 8A and 8B
demonstrates that significant light absorption based on charge
transfer interaction occurs at around 500 nm and around 1300 nm
when NPB is used for the composite material (furthermore, as the
concentration of molybdenum oxide increases, the peak intensity
increases), whereas this problem can be solved when DBT3P-II is
used. Note that the HOMO level of NPB (measured by photoelectron
spectroscopy) is -5.4 eV and the HOMO level of DBT3P-II is -5.9 eV.
This also indicates that NPB is more likely to have charge transfer
interaction as compared to DBT3P-II.
[0373] In this manner, the likelihood of occurrence of charge
transfer interaction can be found from an absorption spectrum; in
this example, qualitative and quantitative evaluations by ESR
measurement were further conducted to examine a difference between
the composite material of one embodiment of the present invention
and the conventional composite material. The details will be
described below.
(Samples for ESR Measurement)
[0374] Samples 1 to 6 and Comparative Samples 1 to 13 of this
example will be described.
[0375] Samples 1 to 6 according to one embodiment of the present
invention are composite films containing a composite material of
DBT3P-II and molybdenum oxide. Comparative Samples 1 to 13 are
composite films containing a composite material of NPB and
molybdenum oxide.
[0376] Every sample was formed by co-evaporating an organic
compound (DBT3P-II or NPB) and molybdenum(VI) oxide over a quartz
substrate. The size of the quartz substrate was 2.8 mm.times.20 mm
(as for Comparative Samples 1 to 3, 3.0 mm.times.20 mm).
[0377] Specifically, the quartz substrate was fixed to a holder in
a vacuum evaporation apparatus so that a surface on which the
composite material was to be deposited faced downward. The pressure
in the vacuum evaporation apparatus was reduced to 10.sup.-4 Pa.
Then, the organic compound (DBT3P-II or NPB) and molybdenum(VI)
oxide were co-evaporated to form a composite film containing a
composite material of the organic compound (DBT3P-II or NPB) and
molybdenum oxide over the quartz substrate. The thickness of the
composite film of each sample was adjusted to 50 nm.
[0378] The molar ratio of the organic compound to molybdenum(VI)
oxide of each sample was adjusted with deposition rates. Table 17
shows the mass ratio and the molar ratio of the organic compound to
molybdenum(VI) oxide of each sample. Note that four samples were
prepared as each sample (eight samples as Comparative Sample 3) and
subjected to ESR measurement in the state where the four samples
(the eight samples in the case of Comparative Sample 3) were
stacked. Table 17 also shows the g-value of each sample.
TABLE-US-00017 TABLE 17 organic mass ratio molar ratio compound
(organic compound:MoOx) g-value Sample 1 DBT3P-II .sup. 4:0.2
1:0.215 2.0054 Sample 2 .sup. 4:0.5 1:0.538 2.0054 Sample 3 4:1
1:1.07 2.0055 Sample 4 4:2 1:2.15 2.0055 Sample 5 4:3 1:3.23 2.0055
Sample 6 4:4 1:4.30 2.0054 Comparative NPB .sup. 4:0.2 1:0.205
2.0026 Sample 1 Comparative 4:1 1:1.03 2.0025 Sample 2 Comparative
4:1 1:1.03 2.0024 Sample 3 Comparative .sup. 4:0.5 1:0.512 2.0023
Sample 4 Comparative 4:1 1:1.03 2.0021 Sample 5 Comparative 4:2
1:2.05 2.0019 Sample 6 Comparative 4:2 1:2.05 2.0020 Sample 7
Comparative 4:2 1:2.05 2.0021 Sample 8 Comparative 4:3 1:3.04
2.0019 Sample 9 Comparative 4:4 1:4.10 2.0016 Sample 10 Comparative
4:4 1:4.10 2.0012 Sample 11 Comparative 4:5 1:5.13 2.0011 Sample 12
Comparative 4:6 1:6.15 2.0011 Sample 13
(ESR Measurement)
[0379] The measurement was performed using an electron spin
resonance spectrometer (JES-FA200, manufactured by JEOL Ltd.) under
the conditions where the resonance frequency was about 9.4 GHz, the
modulation frequency was 100 kHz, the modulation width was 0.6 mT,
the time constant was 0.1 sec, the sweep time was 4 min., and the
measurement temperature was room temperature. Magnetic field
correction was performed with reference to the positions of
Mn.sup.2+ third and fourth signals. The intensity of a measured
electron spin resonance (ESR) spectrum reflects the number of
unpaired electrons, and the likelihood of occurrence of charge
transfer interaction between the organic compound and molybdenum
oxide can be indirectly found out by comparing the intensities of
spectra. Note that g-values each calculated from the peak of the
ESR spectrum range from 2.001 to 2.006 and are in the neighborhood
of the g-value of a free electron (2.0023).
(Results of Measurement)
[0380] FIG. 41 shows ESR spectra of Sample 6 and Comparative Sample
11. In FIG. 41, the horizontal axis represents magnetic field
(unit: mT) and the vertical axis represents intensity.
[0381] As can be seen from FIG. 41, the intensity of Sample 6 at a
magnetic field of around 336 mT to 340 mT is extremely lower than
that of Comparative Sample 11. The lower the intensity is, the
smaller the number of unpaired electrons generated by charge
transfer interaction in the composite material is. That is, it can
be said that Sample 6 is less likely to have charge transfer
interaction in the composite material, as compared to Comparative
Sample 11.
[0382] The results indicate that the composite material including
DBT3P-II and molybdenum oxide, which is the composite material of
one embodiment of the present invention, is less likely to have
charge transfer interaction as compared to the composite material
including NPB and molybdenum oxide and can suppress the occurrence
of light absorption based on the charge transfer interaction.
[0383] FIGS. 42A and 42B are graphs showing the relationship
between the molar ratio of molybdenum(VI) oxide to the organic
compound of each sample and the ratio (A/B) of a positive peak
value (A) to a negative peak value (B) of the ESR spectrum of each
sample. As an example, A and B of Comparative Sample 11 are shown
in FIG. 41. In FIGS. 42A and 42B, the horizontal axis represents
the value of X in the molar ratio of the organic compound to
molybdenum(VI) oxide (1:X (=organic compound:molybdenum oxide)) of
each sample, and the vertical axis represents the value of A/B of
each sample.
[0384] FIG. 42A is a graph of Samples 1 to 6 each including
DBT3P-II as the organic compound, and FIG. 42B is a graph of
Comparative Samples 1 to 13 each including NPB as the organic
compound.
[0385] As can be seen from FIGS. 42A and 42B, many of Samples 1 to
6 have values of A/B at around 1.0, and many of Comparative Samples
1 to 13 have values of A/B at around 1.1 to 1.2. This means that
the shape of the ESR spectrum of the composite material including
DBT3P-II and molybdenum oxide, which is the composite material of
one embodiment of the present invention, at around the positive
peak and the negative peak is symmetrical, whereas that of the
composite material including NPB and molybdenum oxide is
asymmetrical.
[0386] It can be considered that in the case where the shape of the
ESR spectrum at around the positive peak and the negative peak is
symmetrical, unpaired electrons are localized in the composite
material, whereas in the case where the shape is asymmetrical,
unpaired electrons are delocalized as in a semiconductor.
[0387] Here, Table 17 shows that the g-values of Samples 1 to 6
range from 2.005 to 2.006 and the g-values of Comparative Samples 1
to 13 range from 2.001 to 2.003. The g-value is affected by spin
orbit interaction of an atom in the vicinity of an unpaired
electron and therefore becomes large if there is a heavy atom
nearby. This indicates that in Samples 1 to 6, unpaired electrons
are greatly affected by sulfur atoms (S) of DBT3P-II, whereas in
Comparative Samples 1 to 13, unpaired electrons are affected by
nitrogen atoms (N) or carbon atoms (C) of NPB.
(Consideration)
[0388] From the intensity and the symmetry of peaks of the ESR
spectrum, and the g-value obtained above, consideration will be
given as follows.
[0389] First, high intensity of the ESR spectrum of the composite
material including NPB indicates high likelihood of occurrence of
charge transfer interaction. In Comparative Samples 1 to 13, it can
be considered that molybdenum oxide takes electrons from NPB,
whereby unpaired electrons are generated mainly at nitrogen atoms
and the unpaired electrons are delocalized over the nitrogen atoms
or adjacent carbon atoms. This is because of a relatively small
g-value and an asymmetrical shape of the ESR spectrum at around the
positive peak and the negative peak.
[0390] Here, on the orbital where the unpaired electrons exist,
there is the absence of electrons, i.e., holes are generated, and
this means that the holes are also delocalized. Therefore, it can
be estimated that it is easy for holes to move through a conjugated
system that extends from a nitrogen atom to a benzene ring and even
to move between molecules (this is the reason for the excellent
hole-transport property of an aromatic amine). That is, holes
generated at NPB serve as carriers that directly contribute to
conduction.
[0391] The above consideration indicates that NPB is likely to have
charge transfer interaction through nitrogen atoms and holes
generated at NPB due to the charge transfer interaction directly
contribute to carrier-transport and/or carrier-injection
properties.
[0392] On the other hand, low intensity of the ESR spectrum of the
composite material including DBT3P-II suggests almost no occurrence
of charge transfer interaction. It can be considered that in
Samples 1 to 6, molybdenum oxide takes electrons from DBT3P-II,
whereby a very small number of unpaired electrons are generated at
sulfur atoms, but the unpaired electrons are localized at sulfur
atoms. This is because of a relatively large g-value and a
symmetrical shape of the ESR spectrum at around the positive peak
and the negative peak.
[0393] Here, on the orbital where the unpaired electrons exist,
there is the absence of electrons, i.e., holes are generated, and
this means that the holes are also localized. Therefore, a small
number of holes generated at sulfur atoms also remain at the sulfur
atoms and are not likely to serve as carriers that contribute to
conduction. The above consideration indicates that in DBT3P-II,
charge transfer interaction is unlikely to occur, and even if holes
are generated at DBT3P-II, they are unlikely to serve as
carriers.
[0394] However, the composite material including DBT3P-II can
inject and/or transport holes by voltage application. This can be
explained as follows. That is, it can be considered that in such
composite materials as in Samples 1 to 6, by voltage application,
molybdenum oxide further takes electrons from DBT3P-II and unpaired
electrons are generated (i.e., holes are generated) not at sulfur
atoms but at carbon atoms this time. The holes are considered to be
delocalized due to TE bonds between carbon atoms and move through a
conjugated system that extends over a dibenzothiophene ring (or a
benzene ring). This indicates that the composite material including
DBT3P-II can exhibit excellent carrier-transport and/or
carrier-injection properties despite the fact that charge transfer
interaction is unlikely to occur. In fact, as described in the
above examples, a light-emitting element including the composite
material of one embodiment of the present invention exhibits high
emission efficiency.
[0395] As described above, this example indicates that in the
composite material of one embodiment of the present invention,
charge transfer interaction is unlikely to occur, and the composite
material can suppress the occurrence of light absorption based on
the charge transfer interaction. This example also indicates a
mechanism by which the composite material of one embodiment of the
present invention exhibits excellent carrier-injection and/or
carrier-transport properties despite the fact that charge transfer
interaction is unlikely to occur.
REFERENCE EXAMPLE 1
[0396] A method of synthesizing
4-[4-(9-phenyl-9H-fluoren-9-yl)phenyl]-6-phenyldibenzothiophene
(abbreviation: DBTFLP-IV) used in the above example will be
described. A structure of DBTFLP-IV is illustrated below.
##STR00019##
[0397] To a 100 mL three-neck flask were added 1.6 g (4.0 mmol) of
9-(4-bromophenyl)-9-phenyl-9H-fluorene, 1.2 g (4.0 mmol) of
4-phenyl-dibenzothiophene-6-boronic acid, 4.0 mg (20 .mu.mol) of
palladium(II) acetate, 12 mg (40 .mu.mol) of
tri(ortho-tolyl)phosphine, 30 mL of toluene, 3 mL of ethanol, and 3
mL of a 2 mol/L aqueous potassium carbonate solution. This mixture
was degassed while being stirred under reduced pressure, and was
then reacted by being heated and stirred under a nitrogen
atmosphere at 90.degree. C. for 6 hours.
[0398] After the reaction, 150 mL of toluene was added to this
reaction mixture solution, and the organic layer was filtered
through Florisil (produced by Wako Pure Chemical Industries, Ltd.,
Catalog No. 540-00135), alumina (produced by Merck & Co., Inc.,
neutral), and Celite (produced by Wako Pure Chemical Industries,
Ltd., Catalog No. 531-16855) in this order to give a filtrate. The
obtained residue was purified by silica gel column chromatography
(with a developing solvent of toluene and hexane in a 1:3 ratio).
The obtained fraction was concentrated, and acetone and methanol
were added thereto. The mixture was irradiated with ultrasonic
waves and then recrystallized to give 1.6 g of a white powder in a
yield of 73%, which was the object of the synthesis. A reaction
scheme of the above synthesis method is illustrated in the
following (A-1).
##STR00020##
[0399] The Rf values of the substance that was the object of the
synthesis and 9-(4-bromophenyl)-9-phenyl-9H-fluorene were
respectively 0.40 and 0.48, which were found by silica gel thin
layer chromatography (TLC) (with a developing solvent of ethyl
acetate and hexane in a 1:10 ratio).
[0400] This compound was identified as DBTFLP-IV, which was the
object of the synthesis, by nuclear magnetic resonance (NMR)
spectroscopy.
[0401] NMR data of the obtained compound are as follows: .sup.1H
NMR (CDCl.sub.3, 300 MHz): 7.16-7.59 (m, 22H), 7.69-7.71 (m, 2H),
7.79 (d, J=7.5 Hz, 2H), 8.14-8.18 (m, 2H).
REFERENCE EXAMPLE 2
[0402] A method of synthesizing
4,4'-(biphenyl-2,2'-diyl)-bis-dibenzothiophene (abbreviation:
oDBTBP-II) used in the above example will be described. A structure
of oDBTBP-II is illustrated below.
##STR00021##
[0403] To a 100 mL three-neck flask were added 1.6 g (5.0 mmol) of
2,2'-dibromobiphenyl, 3.2 g (11 mmol) of dibenzothiophene-4-boronic
acid, 44 mg (0.2 mmol) of palladium(II) acetate, 120 mg (0.4 mmol)
of tri(ortho-tolyl)phosphine, 30 mL of toluene, 3 mL of ethanol,
and 20 mL of a 2 mol/L aqueous potassium carbonate solution. This
mixture was degassed while being stirred under reduced pressure,
and was then reacted by being heated and stirred under a nitrogen
atmosphere at 90.degree. C. for 10 hours.
[0404] After the reaction, 150 mL of toluene was added to this
reaction mixture solution, and the organic layer was filtered
through Florisil and Celite in this order to give a filtrate. The
obtained residue was purified by silica gel column chromatography
(with a developing solvent of toluene and hexane in a 1:3 ratio).
The obtained fraction was concentrated, and acetone and methanol
were added thereto. The mixture was irradiated with ultrasonic
waves and then recrystallized to give 1.8 g of a white powder of
oDBTBP-II in a yield of 69%, which was the object of the synthesis.
A reaction scheme of the above synthesis method is illustrated in
the following (B-1).
##STR00022##
[0405] The Rf values of oDBTBP-II and 2,2'-dibromobiphenyl were
respectively 0.56 and 0.77, which were found by silica gel thin
layer chromatography (TLC) (with a developing solvent of ethyl
acetate and hexane in a 1:10 ratio).
REFERENCE EXAMPLE 3
[0406] A method of synthesizing
2,8-diphenyl-4-[4-(9-phenyl-9H-fluoren-9-yl)phenyl]dibenzothiophene
(abbreviation: DBTFLP-III) used in the above example will be
described. A structure of DBTFLP-III is illustrated below.
##STR00023##
[0407] To a 100 mL three-neck flask were added 1.6 g (4.0 mmol) of
9-(4-bromophenyl)-9-phenyl-9H-fluorene, 1.7 g (4.4 mmol) of
2,8-diphenyldibenzothiophene-4-boronic acid, 11 mg (0.1 mmol) of
palladium(II) acetate, 30 mg (0.1 mmol) of
tri(ortho-tolyephosphine, 30 mL of toluene, 3 mL of ethanol, and 5
mL of a 2 mol/L aqueous potassium carbonate solution. This mixture
was degassed while being stirred under reduced pressure, and was
then reacted by being heated and stirred under a nitrogen
atmosphere at 90.degree. C. for 6.5 hours.
[0408] After the reaction, 150 mL of toluene was added to this
reaction mixture solution, and the organic layer was filtered
through Florisil, alumina, and Celite in this order to give a
filtrate. The obtained residue was purified by silica gel column
chromatography (with a developing solvent of toluene and hexane in
a 1:3 ratio). The obtained fraction was concentrated, and acetone
and methanol were added thereto. The mixture was irradiated with
ultrasonic waves and then recrystallized to give 2.3 g of a white
powder in a yield of 90%, which was the object of the synthesis. A
reaction scheme of the above synthesis method is illustrated in the
following (C-1).
##STR00024##
[0409] The Rf values of the substance that was the object of the
synthesis and 9-(4-bromophenyl)-9-phenyl-9H-fluorene were
respectively 0.33 and 0.60, which were found by silica gel thin
layer chromatography (TLC) (with a developing solvent of ethyl
acetate and hexane in a 1:10 ratio).
[0410] This compound was identified as DBTFLP-III, which was the
object of the synthesis, by nuclear magnetic resonance (NMR)
spectroscopy.
[0411] .sup.1H NMR data of the obtained compound are as follows:
.sup.1H NMR (CDCl.sub.3, 300 MHz): 7.23-7.52 (m, 20H), 7.65-7.76
(m, 8H), 7.81 (d, J=6.9 Hz, 1H), 7.88 (d, J=8.1 Hz, 1H), 8.40 (dd,
J=11.7 Hz, 1.5 Hz, 2H).
REFERENCE EXAMPLE 4
[0412] A method of synthesizing
3,6-di-(dibenzothiophen-4-yl)-9-phenyl-9H-carbazole (abbreviation:
DBT2PC-II) used in the above example will be described. A structure
of DBT2PC-II is illustrated below.
##STR00025##
[0413] To a 200 mL three-neck flask were added 2.0 g (5.0 mmol) of
3,6-dibromo-9-phenyl-9H-carbazole, 3.2 g (11 minol) of
dibenzothiophene-4-boronic acid, 10 mg (0.1 mmol) of palladium(II)
acetate, 30 mg (0.1 mmol) of tri(ortho-tolyl)phosphine, 50 mL of
toluene, 5 mL of ethanol, and 7.5 mL of a 2 mol/L aqueous potassium
carbonate solution. This mixture was degassed while being stirred
under reduced pressure, and reacted by being heated and stirred
under a nitrogen atmosphere at 90.degree. C. for 6 hours. After the
reaction, this reaction mixture solution was cooled to room
temperature, and then filtered to give a residue while being washed
with water, ethanol, toluene, and hexane in this order. The
obtained residue was purified by silica gel column chromatography
(with a developing solvent of toluene and hexane in a 1:3 ratio).
The obtained fraction was concentrated, and acetone and ethanol
were added thereto. The mixture was irradiated with ultrasonic
waves and then recrystallized to give 1.4 g of a white powder in a
yield of 47%. A reaction scheme of the above synthesis method is
illustrated in the following (D-1).
##STR00026##
[0414] The white powder obtained was subjected to nuclear magnetic
resonance (NMR) spectroscopy. The measurement data are as follows:
.sup.1H NMR (CDCl.sub.3, 300 MHz): .delta. (ppm)=7.44-7.70 (m,
15H), 7.82-7.86 (m, 4H), 8.15-8.22 (m, 4H), 8.57 (d, J=1.5 Hz,
2H).
REFERENCE EXAMPLE 5
[0415] A method of synthesizing
4-[3-(9,10-diphenyl-2-anthryl)phenyl]dibenzothiophene
(abbreviation: 2mDBTPPA-II) used in the above example will be
described. A structure of 2mDBTPPA-II is illustrated below.
##STR00027##
[0416] The method of synthesizing 2mDBTPPA-II is represented by
Synthesis Scheme (E-1), and detailed reaction in the synthesis will
be detailed below.
##STR00028##
[0417] In a 100 mL three-neck flask were put 1.6 g (4.0 mmol) of
2-bromo-9,10-diphenylanthracene, 1.2 g (4.0 mmol) of
3-(dibenzothiophen-4-yl)phenylboronic acid, and 0.30 g (1.0 mmol)
of tri(ortho-tolyl)phosphine. The air in the flask was replaced
with nitrogen. To this mixture were added 25 mL of toluene, 5.0 mL
of ethanol, and 5.0 mL of a 2.0 mol/L aqueous potassium carbonate
solution. While the pressure was reduced, this mixture was degassed
by being stirred.
[0418] Then, 45 mg (0.20 mmol) of palladium(II) acetate was added
to this mixture, and the mixture was stirred under a nitrogen
stream at 80.degree. C. for 5 hours. Then, the aqueous layer of
this mixture was extracted with toluene, and the solution of the
extract and the organic layer were combined and washed with a
saturated aqueous sodium chloride solution. The organic layer was
dried with magnesium sulfate. Then, this mixture was gravity
filtered. The obtained filtrate was concentrated to give an oily
substance. The obtained oily substance was purified by silica gel
column chromatography. The chromatography was carried out using a
mixed solvent of hexane and toluene in a 5:1 ratio as a developing
solvent. The obtained solid was recrystallized with a mixed solvent
of toluene and hexane to give 1.6 g of a yellow powder in a yield
of 70%, which was the the object of synthesis.
[0419] By a train sublimation method, 1.6 g of the obtained yellow
powder solid was purified. In the sublimation purification, the
yellow powder solid was heated at 290.degree. C. under a pressure
of 3.0 Pa with a flow rate of argon at 4.0 mL/min. After the
sublimation purification, 1.4 g of a yellow solid, which was the
object of the synthesis, was obtained in a yield of 87%.
[0420] This compound was identified as
4-[3-(9,10-diphenyl-2-anthryl)phenyl]dibenzothiophene
(abbreviation: 2mDBTPPA-II), which was the object of the synthesis,
by nuclear magnetic resonance (NMR) spectroscopy.
[0421] .sup.1H NMR data of the obtained substance are as follows:
.sup.1H NMR (CDCl.sub.3, 300 MHz): .delta.=7.33 (q, J1=3.3 Hz, 2H),
7.46-7.73 (m, 20H), 7.80-7.87 (m, 2H), 7.99 (st, J1=1.8 Hz, 1H),
8.03 (sd, J1=1.5 Hz, 1H), 8.14-8.20 (m, 2H).
REFERENCE EXAMPLE 6
[0422] A method of synthesizing
4-[3-(9,10-diphenyl-2-anthryl)phenyl]dibenzofuran (abbreviation:
2mDBFPPA-II) used in the above example will be described. A
structure of 2mDBFPPA-II is illustrated below.
##STR00029##
[0423] The method of synthesizing 2mDBFPPA-II is represented by
Synthesis Scheme (F-1), and detailed reaction in the synthesis will
be detailed below.
##STR00030##
[0424] In a 100 mL three-neck flask were put 1.2 g (3.0 mmol) of
2-bromo-9,10-diphenylanthracene, 0.87 g (3.0 mmol) of
3-(dibenzofuran-4-yl)phenylboronic acid, and 0.23 g (0.75 mmol) of
tri(ortho-tolyl)phosphine. The air in the flask was replaced with
nitrogen. To this mixture were added 15 mL of toluene, 5.0 mL of
ethanol, and 3.0 mL of a 2.0 mol/L aqueous potassium carbonate
solution. While the pressure was reduced, this mixture was degassed
by being stirred.
[0425] Then, 34 mg (0.15 mmol) of palladium(II) acetate was added
to this mixture, and the mixture was stirred under a nitrogen
stream at 80.degree. C. for 4 hours. Then, the aqueous layer of
this mixture was extracted with ethyl acetate, and the solution of
the extract and the organic layer were combined and washed with a
saturated aqueous sodium chloride solution. The organic layer was
dried with magnesium sulfate. Then, this mixture was gravity
filtered. The obtained filtrate was concentrated, and the obtained
solid was purified by silica gel column chromatography. The
chromatography was carried out using a mixed solvent of hexane and
toluene in a 5:1 ratio as a developing solvent. The obtained solid
was recrystallized with a mixed solvent of toluene and hexane to
give 1.4 g of a yellow powder in a yield of 79%, which was the
object of synthesis.
[0426] By a train sublimation method, 1.4 g of the obtained yellow
powder solid was purified. In the sublimation purification, the
yellow powder solid was heated at 270.degree. C. under a pressure
of 3.0 Pa with a flow rate of argon at 4.0 mL/min. After the
sublimation purification, 1.1 g of a yellow solid, which was the
object of the synthesis, was obtained in a yield of 81%.
[0427] This compound was identified as
4-[3-(9,10-diphenyl-2-anthryl)phenyl]dibenzofuran (abbreviation:
2mDBFPPA-II), which was the object of the synthesis, by nuclear
magnetic resonance (NMR) spectroscopy.
[0428] .sup.1H NMR data of the obtained substance are as follows:
.sup.1H NMR (CDCl.sub.3, 300 MHz): .delta.=7.31-7.67 (m, 19H),
7.69-7.73 (m, 3H), 7.80-7.86 (m, 2H), 7.95 (dd, J1=0.90 Hz, J2=1.8
Hz, 1H), 7.98-8.01 (m, 2H), 8.07 (s, 1H).
REFERENCE EXAMPLE 7
[0429] A method of synthesizing
4-phenyl-4`-(9-phenylfluoren-9-yl)triphenylamine (abbreviation:
BPAFLP) used in the above example will be specifically described. A
structure of BPAFLP is illustrated below.
##STR00031##
Step 1: Method of Synthesizing
9-(4-Bromophenyl)-9-phenylfluorene
[0430] In a 100 mL three-neck flask, 1.2 g (50 mmol) of magnesium
was activated by being heated and stirred for 30 minutes under
reduced pressure. The activated magnesium was cooled to room
temperature, and the flask was made to contain a nitrogen
atmosphere. Then, several drops of dibromoethane were added, so
that foam formation and heat generation were confirmed. After 12 g
(50 mmol) of 2-bromobiphenyl dissolved in 10 mL of diethyl ether
was slowly added dropwise to this mixture, the mixture was heated
and stirred under reflux for 2.5 hours, so that a Grignard reagent
was prepared.
[0431] In a 500 mL three-neck flask were placed 10 g (40 mmol) of
4-bromobenzophenone and 100 mL of diethyl ether. After the Grignard
reagent which was synthesized in advance was slowly added dropwise
to this mixture, the mixture was heated and stirred under reflux
for 9 hours.
[0432] After reaction, this mixture solution was filtered to give a
residue. The obtained residue was dissolved in 150 mL of ethyl
acetate, and 1N-hydrochloric acid was added to the mixture until it
was made acid, which was then stirred for 2 hours. The organic
layer of this liquid was washed with water, and magnesium sulfate
was added thereto to remove moisture. This suspension was filtered,
and the obtained filtrate was concentrated to give a highly viscous
substance.
[0433] In a 500 mL recovery flask were placed this highly viscous
substance, 50 mL of glacial acetic acid, and 1.0 mL of hydrochloric
acid. The mixture was reacted by being stirred and heated at
130.degree. C. for 1.5 hours under a nitrogen atmosphere.
[0434] After the reaction, this reaction mixture solution was
filtered to give a residue. The obtained residue was washed with
water, an aqueous sodium hydroxide solution, water, and methanol in
this order. Then, the mixture was dried, so that the substance
which was the object of the synthesis was obtained as 11 g of a
white powder in a yield of 69%. A reaction scheme of the above
synthesis method is illustrated in the following (G-1).
##STR00032##
Step 2: Method of Synthesizing
4-Phenyl-4'-(9-phenylfluoren-9-yl)triphenylamine (Abbreviation:
BPAFLP)
[0435] In a 100 mL three-neck flask were placed 3.2 g (8.0 mmol) of
9-(4-bromophenyl)-9-phenylfluorene, 2.0 g (8.0 mmol) of
4-phenyl-diphenylamine, 1.0 g (10 mmol) of sodium tert-butoxide,
and 23 mg (0.04 mmol) of bis(dibenzylideneacetone)palladium(0), and
the air in the flask was replaced with nitrogen. Then, 20 mL of
dehydrated xylene was added to this mixture. After the mixture was
degassed while being stirred under reduced pressure, 0.2 mL (0.1
mmol) of tri(tert-butyl)phosphine (a 10 wt % hexane solution) was
added to the mixture. This mixture was reacted by being stirred and
heated at 110.degree. C. for 2 hours under a nitrogen
atmosphere.
[0436] After the reaction, 200 mL of toluene was added to this
reaction mixture solution, and this suspension was filtered through
Florisil and Celite. The obtained filtrate was concentrated, and
the resulting substance was purified by silica gel column
chromatography (with a developing solvent of toluene and hexane in
a 1:4 ratio). The obtained fraction was concentrated, and acetone
and methanol were added thereto. The mixture was irradiated with
ultrasonic waves and then recrystallized, so that the substance
which was the object of the synthesis was obtained as 4.1 g of a
white powder in a yield of 92%. A reaction scheme of the above
synthesis method is illustrated in the following (G-2).
##STR00033##
[0437] The Rf values of the substance that was the object of the
synthesis, 9-(4-bromophenyl)-9-phenylfluorene, and
4-phenyl-diphenylamine were respectively 0.41, 0.51, and 0.27,
which were found by silica gel thin layer chromatography (TLC)
(with a developing solvent of ethyl acetate and hexane in a 1:10
ratio).
[0438] The compound obtained in Step 2 as described above was
subjected to nuclear magnetic resonance (NMR) spectroscopy. The
measurement data are shown below. The measurement results indicate
that the obtained compound was BPAFLP (abbreviation), which is a
fluorene derivative.
[0439] .sup.1H NMR (CDCl.sub.3, 300 MHz): .delta. (ppm)=6.63-7.02
(m, 3H), 7.06-7.11 (m, 6H), 7.19-7.45 (m, 18H), 7.53-7.55 (m, 2H),
7.75 (d, J=6.9 Hz, 2H).
REFERENCE EXAMPLE 8
[0440] A method of synthesizing
N,N'-bis[4-(9-phenyl-9H-fluoren-9-yl)phenyl]-N,N'-diphenylpyrene-1,6-diam-
ine (abbreviation: 1,6FLPAPrn) used in the above example will be
specifically described. A structure of 1,6FLPAPrn is illustrated
below.
##STR00034##
[0441] In a 300 mL three-neck flask were put 3.0 g (8.3 mmol) of
1,6-dibromopyrene and 6.8 g (17 mmol) of
4-(9-phenyl-9H-fluoren-9-yl)diphenylamine (abbreviation: FLPA). The
air in the flask was replaced with nitrogen. To this mixture were
added 100 mL of toluene, 0.10 mL of a 10 wt % hexane solution of
tri(tert-butyl)phosphine, and 2.4 g (25 nunol) of sodium
tert-butoxide. This mixture was degassed while being stirred under
reduced pressure. This mixture was heated at 80.degree. C., and
after the confirmation that the material was dissolved, 48 mg
(0.083 mmol) of bis(dibenzylideneacetone)palladium(0) was added.
This mixture was stirred at 80.degree. C. for 1.5 hours. After the
stirring, the precipitated yellow solid was collected through
suction filtration without cooling the mixture. The obtained solid
was suspended in 3 L of toluene and heated at 110.degree. C. This
suspension was suction filtered through alumina, Celite, and
Florisil while the temperature of the suspension was kept at
110.degree. C. Further, the suspension was processed with 200 mL of
toluene which had been heated to 110.degree. C. The resulting
filtrate was concentrated to about 300 mL, which was then
recrystallized. Accordingly, 5.7 g of the substance which was the
object of the synthesis was obtained in a yield of 67%.
[0442] By a train sublimation method, 3.56 g of the obtained yellow
solid was purified. Under a pressure of 5.0 Pa with a flow rate of
argon at 5.0 mL/min, the sublimation purification was carried out
at 353.degree. C. After the sublimation purification, 2.54 g of a
yellow solid, which was the object of the synthesis, was obtained
in a yield of 71%. A reaction scheme of the above synthesis method
is illustrated in the following (H-1).
##STR00035##
[0443] The compound obtained in the synthesis example was
identified as
N,N'-bis[4-(9-phenyl-9H-fluoren-9-yl)phenyl]-N,N'-diphenylpyrene-1,6-diam-
ine (abbreviation: 1,6FLPAPrn), which was the object of the
synthesis, by nuclear magnetic resonance (NMR) spectroscopy and
mass spectrometry.
[0444] .sup.1H NMR data of the compound obtained in the above
synthesis example are as follows: .sup.1H NMR (CDCl.sub.3, 300
MHz): .delta.=6.88-6.91 (m, 6H), 7.00-7.03 (m, 8H), 7.13-7.40 (m,
26H), 7.73-7.80 (m, 6H), 7.87 (d, J=9.0 Hz, 2H), 8.06-8.09 (m,
4H).
REFERENCE EXAMPLE 9
[0445] A method of synthesizing
3-[4-(9-phenanthryl)-phenyl]-9-phenyl-9H-carbazole (abbreviation:
PCPPn) will be specifically described. A structure of PCPPn is
illustrated below.
##STR00036##
Step 1: Method of Synthesizing
4-(9-Phenyl-9H-carbazol-3-yl)phenylboronic acid
[0446] In a 300 mL three-neck flask, 8.0 g (20 mmol) of
3-(4-bromophenyl)-9-phenyl-9H-carbazole was placed, the atmosphere
in the flask was replaced with nitrogen, 100 mL of dehydrated
tetrahydrofuran (abbreviation: THF) was added, and the temperature
was lowered to -78.degree. C. Into this mixture solution, 15 mL (24
mmol) of a 1.65 mol/L n-butyllithium hexane solution was dropped,
and the mixture solution with the n-butyllithium hexane solution
added was stirred for 2 hours. To this mixture, 3.4 mL (30 mmol) of
trimethyl borate was added, and the mixture was stirred at
-78.degree. C. for 2 hours and at room temperature for 18 hours.
After the reaction, a 1M diluted hydrochloric acid was added to
this reaction solution until the solution became acid, and the
solution with the diluted hydrochloric acid added was stirred for 7
hours. This solution was subjected to extraction with ethyl
acetate, and the obtained organic layer was washed with a saturated
aqueous sodium chloride solution. After the washing, magnesium
sulfate was added to the organic layer to adsorb moisture. This
suspension was filtrated, and the obtained filtrate was
concentrated, and hexane was added thereto. The mixture was
irradiated with supersonic waves and then recrystallized to give
6.4 g of a white powder in a yield of 88%, which was the object of
synthesis. A reaction scheme of Step 1 described above is
illustrated in the following (I-1).
##STR00037##
[0447] The Rf values of the substance that was the object of
synthesis and 3-(4-bromophenyl)-9-phenyl-9H-carbazole were
respectively 0 (origin) and 0.53, which were found by silica gel
thin layer chromatography (TLC) (with a developing solvent of ethyl
acetate and hexane in a 1:10 ratio). In addition, the Rf values of
the object of the synthesis and
3-(4-bromophenyl)-9-phenyl-9H-carbazole were respectively 0.72 and
0.93, which were found by silica gel thin layer chromatography
(TLC) using ethyl acetate as a developing solvent.
(Step 2: Method of Synthesizing
3-[4-(9-Phenanthryl)-phenyl]-9-phenyl-9H-carbazole (abbreviation:
PCPPn)
[0448] In a 200 mL three-neck flask, a mixture of 1.5 g (5.0 mmol)
of 9-phenyl-9H-carb azol-3-yl-phenyl-4-boronic acid, 3.2 g (11
mmol) of 9-bromophenanthrene, 11 mg (0.1 mmol) of palladium(II)
acetate, 30 mg (0.1 mmol) of tri(ortho-tolyl)phosphine, 30 mL of
toluene, 3 mL of ethanol, and 5 mL of a 2 mol/L aqueous potassium
carbonate solution was degassed while being stirred under reduced
pressure, and reacted by being stirred and heated at 90.degree. C.
for 6 hours under a nitrogen atmosphere.
[0449] After the reaction, 200 mL of toluene was added to this
reaction mixture solution, and the organic layer of the mixture
solution was filtered through Florisil, alumina, and Celite. The
obtained filtrate was washed with water, and magnesium sulfate was
added thereto so that moisture was adsorbed. This suspension was
filtered to obtain a filtrate. The obtained filtrate was
concentrated and purified by silica gel column chromatography. At
this time, a mixed solvent of toluene and hexane
(toluene:hexane=1:4) was used as a developing solvent for the
chromatography. The obtained fraction was concentrated, and acetone
and methanol were added thereto. The mixture was irradiated with
ultrasonic waves and then recrystallized, so that the substance
which was the object of the synthesis was obtained as 2.2 g of a
white powder in a yield of 75%. A reaction scheme of Step 2 is
illustrated in the following (I-2).
##STR00038##
[0450] The Rf values of the substance that was the object of the
synthesis and 9-bromophenanthrene were respectively 0.33 and 0.70,
which were found by silica gel thin layer chromatography (TLC)
(with a developing solvent of ethyl acetate and hexane in a 1:10
ratio).
[0451] The obtained compound was subjected to nuclear magnetic
resonance (NMR) spectroscopy. The measurement data are as follows:
.sup.1H NMR (CDCl.sub.3, 300 MHz): .delta. (ppm)=7.30-7.35 (m,
11H), 7.43-7.78 (m, 16H), 7.86-7.93 (m, 311), 8.01 (dd, J=0.9 Hz,
7.8 Hz, 1H), 8.23 (d, J=7.8 Hz, 1H), 8.47 (d, J=1.5 Hz, 1H), 8.74
(d, J=8.1 Hz, 1H), 8.80 (d, J=7.8 Hz, 1H).
REFERENCE EXAMPLE 10
[0452] A method of synthesizing
3-[4-(dibenzothiophen-4-yl)-phenyl]-9-phenyl-9H-carbazole
(abbreviation: DBTPPC-II) will be specifically described. A
structure of DBTPPC-II is illustrated below.
##STR00039##
[0453] In a 100 mL three-neck flask, a mixture of 2.4 g (6.0 mmol)
of 3-(4-bromophenyl)-9-phenyl-9H-carbazole, 1.7 g (6.0 mmol) of
dienzothiophene-4-boronic acid, 13 mg (0.1 mmol) of palladium(II)
acetate, 36 mg (0.1 mmol) of tri(ortho-tolyl)phosphine, 20 mL of
toluene, 3 mL of ethanol, and 5 mL of a 2 mol/L aqueous potassium
carbonate solution was degassed while being stirred under reduced
pressure, and reacted by being stirred and heated at 90.degree. C.
for 4 hours under a nitrogen atmosphere.
[0454] After the reaction, 200 mL of toluene was added to this
reaction mixture solution, and the organic layer of the mixture
solution was filtered through Florisil (produced by Wako Pure
Chemical Industries, Ltd., Catalog No. 540-00135), alumina
(produced by Merck & Co., Inc., neutral), and Celite (produced
by Wako Pure Chemical Industries, Ltd., Catalog No. 531-16855). The
obtained filtrate was washed with water, and magnesium sulfate was
then added thereto so that moisture was adsorbed. This suspension
was filtered to obtain a filtrate. The obtained filtrate was
concentrated and purified by silica gel column chromatography. A
mixed solvent of toluene and hexane (toluene:hexane=1:4) was used
as a developing solvent for the chromatography. The obtained
fraction was concentrated, and acetone and methanol were added
thereto. The mixture was irradiated with ultrasonic waves and then
recrystallized, so that 2.3 g of a white powder was obtained in a
yield of 77%. A reaction scheme of the above synthesis method is
illustrated in the following (J-1).
##STR00040##
[0455] The Rf values of the white powder obtained by the above
reaction and 3-(4-bromophenyl)-9-phenyl-9H-carbazole were
respectively 0.40 and 0.60, which were found by silica gel thin
layer chromatography (TLC) (with a developing solvent of ethyl
acetate and hexane in a 1:10 ratio).
[0456] The white powder obtained by the above reaction was
subjected to nuclear magnetic resonance (NMR) spectroscopy. The
measurement data are shown below. From the measurement data, the
white powder obtained by the above reaction was identified as
DBTPPC-II which was the object of the synthesis.
[0457] .sup.1H NMR (CDCl.sub.3, 300 MHz): .delta. (ppm)=7.30-7.36
(m, 1H), 7.44-7.52 (m, 6H), 7.55-7.67 (m, 6H), 7.75 (dd, J=8.7 Hz,
1.5 Hz, 1H), 7.85-7.88 (m, 5H), 8.16-8.24 (m, 3H), 8.46 (d, J=1.5
Hz, 1H)
REFERENCE EXAMPLE 11
[0458] A method of synthesizing
3-[3-(dibenzothiophen-4-yl)-phenyl]-9-phenyl-9H-carbazole
(abbreviation: mDBTPPC-II) used in the above example will be
specifically described. A structure of mDBTPPC-II is illustrated
below.
##STR00041##
[0459] In a 100 mL three-neck flask, a mixture of 2.4 g (6.0 mmol)
of 3-(3-bromophenyl)-9-phenyl-9H-carbazole, 1.7 g (6.0 mmol) of
dienzothiophene-4-boronic acid, 13 mg (0.1 mmol) of palladium(II)
acetate, 36 mg (0.1 mmol) of tri(ortho-tolyflphosphine, 20 mL of
toluene, 3 mL of ethanol, and 5 mL of a 2 mol/L aqueous potassium
carbonate solution was degassed while being stirred under reduced
pressure, and reacted by being stirred and heated at 90.degree. C.
for 6 hours under a nitrogen atmosphere.
[0460] After the reaction, 200 mL of toluene was added to this
reaction mixture solution, and the organic layer of the mixture
solution was filtered through Florisil (produced by Wako Pure
Chemical Industries, Ltd., Catalog No. 540-00135), alumina
(produced by Merck & Co., Inc., neutral), and Celite (produced
by Wako Pure Chemical Industries, Ltd., Catalog No. 531-16855). The
obtained filtrate was washed with water, and magnesium sulfate was
then added thereto so that moisture was adsorbed. This suspension
was filtered to obtain a filtrate. The obtained filtrate was
concentrated and purified by silica gel column chromatography. A
mixed solvent of toluene and hexane (toluene:hexane=1:4) was used
as a developing solvent for the chromatography. The obtained
fraction was concentrated, and acetone and hexane were added
thereto. The mixture was irradiated with ultrasonic waves and then
recrystallized, so that 2.6 g of a white powder was obtained in a
yield 87%. A reaction scheme of the above synthesis method is
illustrated in the following (K-1).
##STR00042##
[0461] The Rf values of the white powder obtained by the above
reaction and 3-(3-bromophenyl)-9-phenyl-9H-carbazole were
respectively 0.38 and 0.54, which were found by silica gel thin
layer chromatography (TLC) (with a developing solvent of ethyl
acetate and hexane in a 1:10 ratio).
[0462] The white powder obtained by the above reaction was
subjected to nuclear magnetic resonance (NMR) spectroscopy. The
measurement data are shown below. From the measurement data, the
white powder obtained by the above reaction was identified as
mDBTPPC-II which was the object of the synthesis.
[0463] .sup.1H NMR (CDCl.sub.3, 300 MHz): .delta. (ppm)=7.27-7.33
(m, 1H), 7.41-7.51 (m, 6H), 7.58-7.65 (m, 7H), 7.70-7.86 (m, 411),
8.12 (t, J 1.5 Hz, 1H), 8.17-8.22 (m, 3H), 8.44 (d, J=1.8 Hz,
1H).
REFERENCE EXAMPLE 12
[0464] A method of synthesizing
4-[4-(9-phenanthryl)phenyl]dibenzothiophene (abbreviation:
DBTPPn-II) will be specifically described. A structure of DBTPPn-II
is illustrated below.
##STR00043##
[0465] In a 50 mL three-neck flask were put 1.2 g (3.6 mmol) of
9-(4-bromophenyl)phenanthrene, 0.8 g (3.5 mmol) of
dibenzothiophene-4-boronic acid, and 53 mg (0.2 mmol) of
tri(ortho-tolyl)phosphine. The air in the flask was replaced with
nitrogen. To this mixture were added 3.5 mL of a 2.0 M aqueous
potassium carbonate solution, 13 mL of toluene, and 4.0 mL of
ethanol. The mixture was degassed by being stirred under reduced
pressure. Then, 8.0 mg (36 .mu.mol) of palladium(II) acetate was
added to this mixture, and the mixture was stirred under a nitrogen
stream at 80.degree. C. for 7 hours. After a predetermined time
elapsed, an organic substance was extracted from the aqueous layer
of the obtained mixture with toluene.
[0466] The solution of the extract and the organic layer were
combined and washed with a saturated aqueous sodium chloride
solution, and dried with magnesium sulfate. This mixture was
separated by gravity filtration, and the filtrate was concentrated
to give an oily substance. This oily substance was purified by
silica gel column chromatography. The column chromatography was
conducted using a developing solvent of hexane and toluene in a
20:1 ratio. The obtained fraction was concentrated to give an oily
substance. This oily substance was recrystallized with a mixed
solvent of toluene and hexane, so that the substance which was the
object of the synthesis was obtained as 0.8 g of a white powder in
a yield of 53%.
[0467] By a train sublimation method, 0.8 g of the obtained white
powder was purified. In the sublimation purification, the white
powder was heated at 240.degree. C. under a pressure of 2.4 Pa with
a flow rate of argon at 5 mL/min. After the sublimation
purification, 0.7 g of a white powder was obtained in a yield of
88%. The above-described synthesis scheme is illustrated in the
following (L-1).
##STR00044##
[0468] This compound was identified as
4-[4-(9-phenanthryl)phenyl]dibenzothiophene (abbreviation:
DBTPPn-II), which was the object of the synthesis, by nuclear
magnetic resonance (NMR) spectroscopy.
[0469] .sup.1H NMR data of the obtained compound are as follows:
.sup.1H NMR (CDCl.sub.3, 300 MHz): .delta. (ppm)=7.46-7.53 (m, 2H),
7.58-7.73 (m, 8H), 7.80 (s, 1H), 7.87-7.96 (m, 4H), 8.07 (d, J=8.1
Hz, 1H), 8.18-8.24 (m, 2H), 8.76 (d, J=8.1 Hz, 1H), 8.82 (d, J=7.8
Hz, 1H).
REFERENCE EXAMPLE 13
[0470] A method of synthesizing
4,4'-{(1,1':2',1'':2'',1'')-quaterphenyl-3,3'''-yl}bisdibenzothiophene
(abbreviation: mZ-DBT2-II) used in the above example will be
described.
##STR00045##
[0471] In a 200 mL three-neck flask, a mixture of 1.0 g (3.2 mmol)
of 2,2'-dibromobiphenyl, 2.1 g (6.7 mmol) of
3-(dibenzothiophen-4-yl)phenylboronic acid, 47 mg (40 .mu.mol) of
tetrakis(triphenylphosphine)palladium(0), 20 mL of toluene, 2 mL of
ethanol, 7 mL of a 2 mol/L aqueous potassium carbonate solution was
degassed while being stirred under reduced pressure, and was then
reacted by being stirred and heated at 85.degree. C. for 6 hours
and then by being stirred and heated at 100.degree. C. for 6 hours
under a nitrogen atmosphere. Further, 47 mg (40 .mu.mol) of
tetrakis(triphenylphosphine)palladium(0) was added to the mixture,
and the mixture was reacted by being stirred and heated at
100.degree. C. for 2 hours under a nitrogen atmosphere.
[0472] After the reaction, 300 mL of toluene was added to this
reaction mixture solution, and the organic layer of the mixture
solution was filtered through Florisil (produced by Wako Pure
Chemical Industries, Ltd., Catalog No. 540-00135), alumina
(produced by Merck & Co., Inc., neutral), and Celite (produced
by Wako Pure Chemical Industries, Ltd., Catalog No. 531-16855). The
obtained filtrate was washed with water, and magnesium sulfate was
added thereto so that moisture was adsorbed. This suspension was
filtered to obtain a filtrate. The obtained filtrate was
concentrated and purified by silica gel column chromatography. At
this time, a mixed solvent of toluene and hexane
(toluene:hexane=1:5) was used as a developing solvent for the
chromatography. The obtained fraction was concentrated, and hexane
was added thereto. The mixture was irradiated with ultrasonic waves
and then recrystallized, so that the substance which was the object
of the synthesis was obtained as 2.2 g of a white powder in a yield
of 51%. A reaction scheme of the above synthesis method is
illustrated in the following (M-1).
##STR00046##
[0473] The Rf value of the substance that was the object of the
synthesis was 0.25, which was found by silica gel thin layer
chromatography (TLC) (with a developing solvent of ethyl acetate
and hexane in a 1:10 ratio).
[0474] This compound was identified as mZ-DBT2-II, which was the
object of the synthesis, by nuclear magnetic resonance (NMR)
spectroscopy.
[0475] .sup.1H NMR data of the obtained compound are as follows:
NMR (CDCl.sub.3, 300 MHz): .delta. (ppm)=6.73 (td, J=0.98 Hz, 1.95
Hz, 7.4 Hz, 2H), 7.01-7.06 (m, 4H), 7.34-7.39 (m, 4H), 7.41-7.47
(m, 11H), 7.53-7.59 (m, 3H), 7.69-7.72 (m, 2H), 7.98 (dd, J=1.5 Hz,
6.8 Hz, 2H), 8.08-8.11 (m, 2H).
REFERENCE EXAMPLE 14
[0476] A method of synthesizing
4-{3-[3-(9-phenyl-9H-fluoren-9-yl)phenyl]phenyl}dibenzofuran
(abbreviation: mmDBFFLBi-II) used in the above example will be
described.
##STR00047##
[0477] In a 200 mL three-neck flask, a mixture of 3.5 g (8.9 mmol)
of 9-(3-bromophenyl)-9-phenylfluorene, 2.8 g (9.8 mmol) of
3-(dibenzofuran-4-yl)phenylboronic acid, 22 mg (0.1 mmol) of
palladium(II) acetate, 89.5 mg (0.3 mmol) of
tri(ortho-tolyl)phosphine, 38 mL of toluene, 3.8 mL of ethanol,
12.7 mL of a 2 mol/L aqueous potassium carbonate solution was
degassed while being stirred under reduced pressure, and was then
reacted by being stirred and heated at 80.degree. C. for 15.5 hours
under a nitrogen atmosphere.
[0478] After the reaction, 300 mL of toluene was added to this
reaction mixture solution, and the organic layer of this mixture
solution was filtered through alumina (produced by Merck & Co.,
Inc., neutral) and Celite (produced by Wako Pure Chemical
Industries, Ltd., Catalog No. 531-16855). The obtained filtrate was
washed with water, and magnesium sulfate was added thereto so that
moisture was adsorbed. This suspension was filtered to obtain a
filtrate. The obtained filtrate was concentrated and purified by
silica gel column chromatography. At this time, a mixed solvent of
toluene and hexane (toluene:hexane=2:5) was used as a developing
solvent for the chromatography. The obtained fraction was
concentrated, and methanol was added thereto. The mixture was
irradiated with ultrasonic waves and then recrystallized to give
3.0 g of a white powder in a yield of 60%, which was the object of
the synthesis. A reaction scheme of the above synthesis method is
illustrated in the following (N-1).
##STR00048##
[0479] The Rf value of the substance that was the object of the
synthesis was 0.33, which was found by silica gel thin layer
chromatography (TLC) (with a developing solvent of ethyl acetate
and hexane in a 1:10 ratio).
[0480] This compound was identified as mmDBFFLBi-II, which was the
object of the synthesis, by nuclear magnetic resonance (NMR)
spectroscopy.
[0481] .sup.1H NMR data of the obtained compound are as follows:
.sup.1H NMR (CDCl.sub.3, 300 MHz): .delta. (ppm)=7.18-7.60 (m,
22H), 7.78 (d, J=6.4 Hz, 2H), 7.85 (td, J=1.5 Hz, 7.3 Hz, 1H), 7.96
(dd, J=1.47 Hz, 7.81 Hz, 1H), 7.99-8.00 (m, 2H).
REFERENCE EXAMPLE 15
[0482] A synthesis example of preparing
3-[4-(1-naphthyl)-phenyl]-9-phenyl-9H-carbazole (abbreviation:
PCPN) used in the above example will be described.
##STR00049##
[0483] A synthesis scheme of PCPN is illustrated in (o-1).
##STR00050##
[0484] In a 200 mL three-neck flask, a mixture of 5.0 g (15.5 mmol)
of 3-bromo-9-phenyl-9H-carbazole, 4.2 g (17.1 mmol) of
4-(1-naphthyl)phenylboronic acid, 38.4 mg (0.2 mmol) of
palladium(II) acetate, 104 mg (0.3 mmol) of
tri(ortho-tolyl)phosphine, 50 mL of toluene, 5 mL of ethanol, and
30 ml. of a 2 mol/L aqueous potassium carbonate solution was
degassed while being stirred under reduced pressure, and reacted by
being stirred and heated at 85.degree. C. for 9 hours under a
nitrogen atmosphere.
[0485] After the reaction, 500 mL of toluene was added to this
reaction mixture solution, and the organic layer of this mixture
solution was filtered through Florisil (produced by Wako Pure
Chemical Industries, Ltd., Catalog No. 540-00135), alumina, and
Celite (produced by Wako Pure Chemical Industries, Ltd., Catalog
No. 531-16855). The obtained filtrate was washed with water, and
magnesium sulfate was added thereto so that moisture was adsorbed.
This suspension was filtered to obtain a filtrate. The obtained
filtrate was concentrated and purified by silica gel column
chromatography. At this time, a mixed solvent of toluene and hexane
(toluene:hexane=1:4) was used as a developing solvent for the
chromatography. The obtained fraction was concentrated, and
methanol was added thereto. The mixture was irradiated with
ultrasonic waves and then recrystallized to give 6.24 g of a white
powder in a yield of 90%, which was the object of the
synthesis.
[0486] This compound was identified as
3-[4-(1-naphthyl)-phenyl]-9-phenyl-9H-carbazole (abbreviation:
PCPN), which was the object of the synthesis, by nuclear magnetic
resonance (.sup.1H-NMR) spectroscopy.
[0487] .sup.1H NMR data of the obtained substance are as follows:
.sup.1H NMR (CDCl.sub.3, 300 MHz): .delta. (ppm)=7.30-7.35 (m, 1H),
7.44-7.67 (m, 14H), 7.76 (dd, J=8.7 Hz, 1.8 Hz, 1H), 7.84-7.95 (m,
4H), 8.04 (d, J=7.8, 1H), 8.23 (d, J=7.8, 1H), 8.46 (d, J=1.5,
1H).
EXPLANATION OF REFERENCE
[0488] 100: substrate, 101: first electrode, 102: EL layer, 108:
second electrode, 401: source side driver circuit, 402: pixel
portion, 403: gate side driver circuit, 404: sealing substrate,
405: sealing material, 407: space, 408: wiring, 409: flexible
printed circuit (FPC), 410: element substrate, 411: switching TFT,
412: current control TFT, 413: first electrode, 414: insulator,
416: EL layer, 417: second electrode, 418: light-emitting element,
423: n-channel TFT, 424: p-channel TFT, 501: substrate, 502: first
electrode, 503: second electrode, 504: EL layer, 505: insulating
layer, 506: partition layer, 701: hole-injection layer, 702:
hole-transport layer, 703: light-emitting layer, 704:
electron-transport layer, 705: electron-injection layer, 706:
electron-injection buffer layer, 707: electron-relay layer, 708:
composite material layer, 800: EL layer, 801: EL layer, 802: EL
layer, 803: charge-generation layer, 811: lighting device, 812:
lighting device, 813: desk lamp, 1100: substrate, 1101: first
electrode, 1103: second electrode, 1111: hole-injection layer,
1111a: first hole-injection layer, 1111b: second hole-injection
layer, 1112: hole-transport layer, 1112a: first hole-transport
layer, 1112b: second hole-transport layer, 1113: light-emitting
layer, 1113a: first light-emitting layer, 1113b: second
light-emitting layer, 1114a: first electron-transport layer, 1114b:
second electron-transport layer, 1115: electron-injection layer,
1115a: first electron-injection layer, 1115b: second
electron-injection layer, 1116: electron-relay layer, 7100:
television device, 7101: housing, 7103: display portion, 7105:
stand, 7107: display portion, 7109: operation key, 7110: remote
controller, 7201: main body, 7202: housing, 7203: display portion,
7204: keyboard, 7205: external connection port, 7206: pointing
device, 7301: housing, 7302: housing, 7303: joint portion, 7304:
display portion, 7305: display portion, 7306: speaker portion,
7307: recording medium insertion portion, 7308: LED lamp, 7309:
operation key, 7310: connection terminal, 7311: sensor, 7312:
microphone, 7400: cellular phone, 7401: housing, 7402: display
portion, 7403: operation button, 7404: external connection port,
7405: speaker, 7406: microphone, 7501: lighting portion, 7502:
shade, 7503: adjustable arm, 7504: support, 7505: base, and 7506:
power switch.
[0489] This application is based on Japanese Patent Application
serial no. 2010-225037 filed with Japan Patent Office on Oct. 4,
2010 and Japanese Patent Application serial no. 2011-122827 filed
with Japan Patent Office on May 31, 2011, the entire contents of
which are hereby incorporated by reference.
* * * * *