U.S. patent application number 12/132143 was filed with the patent office on 2008-12-18 for organometallic complex, and light-emitting element, light-emitting device, and electronic device using the organometallic complex.
This patent application is currently assigned to Semiconductor Energy Labratory Co., Ltd.. Invention is credited to Hideko Inoue, Nobuharu Ohsawa, Satoshi Seo.
Application Number | 20080312437 12/132143 |
Document ID | / |
Family ID | 40132958 |
Filed Date | 2008-12-18 |
United States Patent
Application |
20080312437 |
Kind Code |
A1 |
Inoue; Hideko ; et
al. |
December 18, 2008 |
Organometallic Complex, and Light-Emitting Element, Light-Emitting
Device, and Electronic Device Using the Organometallic Complex
Abstract
According to the present invention, a wider variation of
organometallic complexes that can emit phosphorescence can be
provided by applying, as a ligand, an organic compound from which a
variety of derivatives can be easily synthesized. In particular, an
organometallic complex having a sharp emission spectrum is
provided. Further, an organometallic complex having high emission
efficiency is provided. An organometallic complex represented by
the general formula (G1) is provided. In the formula, Ar represents
an aryl group, R represents an alkoxy group having 1 to 4 carbon
atoms, and R.sup.1 and R.sup.2 individually represent either
hydrogen or an alkyl group having 1 to 4 carbon atoms.
##STR00001##
Inventors: |
Inoue; Hideko; (Atsugi,
JP) ; Seo; Satoshi; (Kawasaki, JP) ; Ohsawa;
Nobuharu; (Zama, JP) |
Correspondence
Address: |
COOK ALEX LTD
SUITE 2850, 200 WEST ADAMS STREET
CHICAGO
IL
60606
US
|
Assignee: |
Semiconductor Energy Labratory Co.,
Ltd.
|
Family ID: |
40132958 |
Appl. No.: |
12/132143 |
Filed: |
June 3, 2008 |
Current U.S.
Class: |
544/225 |
Current CPC
Class: |
C07F 15/0033 20130101;
C09K 11/06 20130101 |
Class at
Publication: |
544/225 |
International
Class: |
C07F 15/00 20060101
C07F015/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 4, 2007 |
JP |
2007-148458 |
Claims
1. An organometallic complex represented by a general formula (G5),
##STR00050## wherein R.sup.3 to R.sup.6 individually represent
hydrogen, an alkyl group, an alkoxy group, a halogen group, a
haloalkyl group, an aryl group, a dialkylamino group, or a
diarylamino group; M is a central metal and represents an element
belonging to Group 9 or Group 10 in the periodic table.
2. The organometallic complex according to claim 1, wherein the M
is iridium or platinum.
3. A light-emitting device including the organometallic complex
according to claim 1.
4. An organometallic complex represented by a general formula (G6),
##STR00051## wherein R.sup.7 and R.sup.8 represent an alkyl group
having 1 to 4 carbon atoms; and M is a central metal and represents
an element belonging to Group 9 or Group 10 in the periodic
table.
5. The organometallic complex according to claim 4, wherein the M
is iridium or platinum.
6. A light-emitting device including the organometallic complex
according to claim 4.
7. An organometallic complex represented by a general formula
(G11), ##STR00052## wherein R.sup.3 to R.sup.6 individually
represent hydrogen, an alkyl group, an alkoxy group, a halogen
group, a haloalkyl group, an aryl group, a dialkylamino group, or a
diarylamino group; M is a central metal and represents an element
belonging to Group 9 or Group 10 in the periodic table; L
represents a monoanionic ligand; and n is 2 when the M is an
element belonging to Group 9, and n is 1 when the M is an element
belonging to Group 10.
8. The organometallic complex according to claim 7, wherein the
monoanionic ligand is any of structural formulae (L1) to (L8).
##STR00053##
9. The organometallic complex according to claim 7, wherein the M
is iridium or platinum.
10. A light-emitting device including the organometallic complex
according to claim 7.
11. An organometallic complex represented by a general formula
(G12), ##STR00054## wherein R.sup.7 and R.sup.8 represent an alkyl
group having 1 to 4 carbon atoms; M is a central metal and
represents an element belonging to Group 9 or Group 10 in the
periodic table; L represents a monoanionic ligand; and n is 2 when
the M is an element belonging to Group 9, and n is 1 when the M is
an element belonging to Group 10.
12. The organometallic complex according to claim 11, wherein the
monoanionic ligand is any of structural formulae (L1) to (L8).
##STR00055##
13. The organometallic complex according to claim 11, wherein the M
is iridium or platinum.
14. A light-emitting device including the organometallic complex
according to claim 11.
Description
TECHNICAL FIELD
[0001] The present invention relates to an organometallic complex.
In particular, the present invention relates to an organometallic
complex that is capable of converting a triplet excited state into
luminescence. In addition, the present invention relates to a
light-emitting element, a light-emitting device and an electronic
device which use the organometallic complex.
BACKGROUND ART
[0002] Organic compounds absorb light, and thereby the compounds
are converted to be in an excited state. By going through this
excited state, such organic compounds generate various reactions
(such as photochemical reactions) in some cases, or luminescence is
produced in some cases. Therefore, various applications of the
organic compounds have been being made.
[0003] As one example of the photochemical reactions, a reaction
(oxygen addition) of singlet oxygen with an unsaturated organic
molecule is known (refer to Reference 1: Haruo INOUE, et al., Basic
Chemistry Course PHOTOCHEMISTRY I (Maruzen Co., Ltd.), pp. 106-110,
for example). Since the ground state of an oxygen molecule is a
triplet state, oxygen in a singlet state (singlet oxygen) is not
generated by direct photoexcitation. However, singlet oxygen is
generated in the presence of any other triplet excited molecule,
which leads to an oxygen addition reaction. In this case, a
compound capable of forming the triplet excited molecule is
referred to as a photosensitizer.
[0004] As described above, in order to generate singlet oxygen, a
photosensitizer that is capable of forming a triplet excited
molecule by photoexcitation is necessary. However, since the ground
state of an ordinary organic compound is a singlet state,
photoexcitation to a triplet excited state is a forbidden
transition, and a triplet excited molecule is hardly generated.
Therefore, as such a photosensitizer, a compound which easily
generates intersystem crossing from the singlet excited state to
the triplet excited state (or a compound which allows the forbidden
transition of photoexcitation directly to the triplet excited
state) is required. In other words, such a compound can be used as
a photosensitizer and is useful.
[0005] Also, such a compound often emits phosphorescence. The
phosphorescence is luminescence generated by transition between
different energies in multiplicity and in the case of an ordinary
organic compound, indicates luminescence generated in returning
from the triplet excited state to the singlet ground state (in
contrast, luminescence in returning from a singlet excited state to
a singlet ground state is referred to as fluorescence). Application
fields of a compound capable of emitting phosphorescence, that is,
a compound capable of converting a triplet excited state into
luminescence (hereinafter, referred to as a phosphorescent
compound), include a light-emitting element using an organic
compound as a light-emitting substance.
[0006] This light-emitting element has a simple structure in which
a light-emitting layer containing an organic compound that is a
light-emitting substance is provided between electrodes, and has
attracted attention as a next-generation flat panel display element
because of its characteristics such as a thin shape, lightweight,
high response speed, and low direct current voltage driving. In
addition, a display device using this light-emitting element is
superior in contrast, image quality, and wide viewing angle.
[0007] The emission mechanism of a light-emitting element in which
an organic compound is used as a light-emitting substance is a
carrier injection type. That is, by applying voltage with a
light-emitting layer interposed between electrodes, electrons and
holes injected from the electrodes are recombined to make the
light-emitting substance excited, and light is emitted when the
excited state returns to the ground state. As in the case of
photoexcitation described above, types of the excited state include
a singlet excited state (S*) and a triplet excited state (T*).
Further, the statistical generation ratio thereof in a
light-emitting element is considered to be S*:T*=1:3.
[0008] At room temperature, as for a compound capable of converting
a singlet excited state to luminescence (hereinafter, referred to
as a fluorescent compound), only luminescence from the singlet
excited state (fluorescence) is observed, but luminescence from the
triplet excited state (phosphorescence) is not observed. Therefore,
in a light-emitting element using a fluorescent compound, the
theoretical limit of internal quantum efficiency (the ratio of
generated photons to injected carriers) is considered to be 25%
based on S*:T*=1.3.
[0009] On the other hand, when the phosphorescent compound
described above is used, the internal quantum efficiency can be
improved to 75 to 100% in theory. Namely, a light emission
efficiency that is 3 to 4 times as much as that of the fluorescence
compound can be achieved. For these reasons, in order to achieve a
highly-efficient light-emitting element, a light-emitting element
using a phosphorescent compound has been developed actively (for
example, refer to Reference 2: Zhang, Guo-Lin, et al., Gaodeng
Xuexiao Huaxue Xuebao (2004), vol. 25, No. 3, pp. 397-400). In
particular, as the phosphorescent compound, an organometallic
complex using iridium or the like as a central metal has been
attracting attention, owing to its high phosphorescence quantum
yield.
DISCLOSURE OF THE INVENTION
[0010] The organometallic complex disclosed in Reference 2 can be
expected to be used as a photosensitizer, since it easily causes
intersystem crossing. In addition, since the organometallic complex
easily generates luminescence (phosphorescence) from a triplet
excited state, a highly efficient light-emitting element is
expected by using the organometallic complex for the light-emitting
element. However, in the present state, the number of types of such
organometallic complexes is small.
[0011] For example, a pyrazine derivative which is used as a ligand
of the organometallic complex disclosed in Reference 2 is
synthesized by a dehydration condensation reaction of
ethylenediamine and .beta.-diketone (benzyl) and a dehydrogenation
reaction following the dehydration condensation reaction; however,
there are limitations on the types of ethylenediamine derivatives
and .beta.-diketone which can be used as raw materials, and thus,
the types of pyrazine derivatives are also limited. Therefore,
naturally, there are also limitations on the types of
organometallic complexes using the pyrazine derivative as a
ligand.
[0012] Further, the organometallic complex disclosed in Reference 2
has a problem in that the emission spectrum is broad. This lowers
the color purity and thus is disadvantageous for application to
full color display devices in terms of color reproductively. This
organometallic complex emits red-orange color light; however, if
the emission spectrum is broad, the spectrum extends to a region of
deep red to infrared, which leads to lower emission efficiency
(visibility efficiency (cd/A)).
[0013] As described above, it is an object of the present invention
to provide a wider variation of organometallic complexes that can
emit phosphorescence by applying, as a ligand, an organic compound
from which a variety of derivatives can be easily synthesized. In
particular, it is another object of the present invention to
provide an organometallic complex by which a light-emitting element
having a sharp emission spectrum can be formed. Further, it is
another object of the present invention to provide an
organometallic complex having high emission efficiency.
[0014] Moreover, it is another object of the present invention to
provide a light-emitting element with wide variations of light
emission of green to red colors by manufacturing a light-emitting
element using such an organometallic complex. It is still another
object of the present invention to provide a light-emitting element
with high color purity. It is still another object of the present
invention to provide a light-emitting element having high
light-emitting efficiency. It is still another object to provide a
light-emitting device and an electronic device with reduced power
consumption.
[0015] The present inventors have made researches keenly. As a
result, the present inventors have invented that a pyrazine
derivative represented by the following general formula (G0) is
ortho-metallated with a metal ion of Group 9 or Group 10 in the
periodic table, and thereby an organometallic complex can be
obtained, the organometallic complex can easily cause intersystem
crossing, and emit phosphorescence. Further, the present inventors
have found that emission spectrum of a light-emitting element
formed using an organometallic complex having the structure of the
general formula (G0) which is ortho-metallated is especially
sharp.
##STR00002##
[0016] In the formula, Ar represents an aryl group, R represents an
alkoxy group having 1 to 4 carbon atoms, R.sup.1 and R.sup.2
individually represent either hydrogen or an alkyl group having 1
to 4 carbon atoms.
[0017] Therefore, a structure of the present invention is an
organometallic complex including a structure represented by a
general formula (G1).
##STR00003##
[0018] In the formula, Ar represents an arylene group; R represents
an alkoxy group having 1 to 4 carbon atoms; R.sup.1 and R.sup.2
individually represent hydrogen or an alkyl group having 1 to 4
carbon atoms; and M is a central metal and represents an element
belonging to Group 9 or Group 10 in the periodic table.
[0019] In addition, when R.sup.2 in the above general formula (G0)
is hydrogen, the pyrazine derivative represented by the general
formula (G0) is easy to be ortho-metallated with a metal ion, since
steric hindrance is small, which is preferable in terms of yield in
synthesis. Accordingly, a preferred structure of the present
invention is an organometallic complex including a structure
represented by the following general formula (G2).
##STR00004##
[0020] In the formula, Ar represents an arylene group; R represents
an alkoxy group having 1 to 4 carbon atoms; R.sup.1 represents
hydrogen or an alkyl group having 1 to 4 carbon atoms; and M is a
central metal and represents an element belonging to Group 9 or
Group 10 in the periodic table.
[0021] Preferably, R.sup.2 and R.sup.1 in the above general formula
(G0) are hydrogen and an alkyl group, respectively, in terms of
yield in synthesis of the organometallic complex. Accordingly, a
preferred structure of the present invention is an organometallic
complex including a structure represented by the following general
formula (G2).
##STR00005##
[0022] In the formula, Ar represents an arylene group; R represents
an alkoxy group having 1 to 4 carbon atoms; R.sup.1 represents an
alkyl group having 1 to 4 carbon atoms; and M is a central metal
and represents an element belonging to Group 9 or Group 10 in the
periodic table.
[0023] In addition, in the organometallic complex having the
structure represented by the above general formula (G2), a
phenylene group is preferable for the arylene group (Ar). By
introducing a substituent to the phenylene group, emission color
with wide region of green color to red color can be realized.
Accordingly, a preferred structure of the present invention is an
organometallic complex including a structure represented by the
following general formula (G3).
##STR00006##
[0024] In the formula, R represents an alkoxy group having 1 to 4
carbon atoms; R.sup.1 represents an alkyl group having 1 to 4
carbon atoms; R.sup.3 to R.sup.6 individually represent hydrogen,
an alkyl group, an alkoxy group, a halogen group, a haloalkyl
group, an aryl group, a dialkylamino group, or a diarylamino group;
M is a central metal and represents an element belonging to Group 9
or Group 10 in the periodic table. In addition, in the
organometallic complex having the structure represented by the
above general formula (G2), conjugation of the arylene group (Ar)
is expanded to obtain red emission color, which is useful.
Accordingly, another preferred structure of the present invention
is an organometallic complex including a structure represented by
the following general formula (G4).
##STR00007##
[0025] In the formula, R represents an alkoxy group having 1 to 4
carbon atoms; R.sup.1 represents an alkyl group having 1 to 4
carbon atoms; R.sup.7 and R.sup.8 represent an alkyl group having 1
to 4 carbon atoms; and M is a central metal and represents an
element belonging to Group 9 or Group 10 in the periodic table.
[0026] In addition, in the organometallic complex having the
structure represented by the above general formula (G3),
specifically, an organometallic complex having a structure
represented by the following general formula (G5) is preferable in
terms of yield in synthesis.
##STR00008##
[0027] In the formula, R.sup.3 to R.sup.6 individually represent
hydrogen, an alkyl group, an alkoxy group, a halogen group, a
haloalkyl group, an aryl group, a dialkylamino group, or a
diarylamino group; M is a central metal and represents an element
belonging to Group 9 or Group 10 in the periodic table.
[0028] In addition, in the organometallic complex having the
structure represented by the above general formula (G4),
specifically, an organometallic complex having a structure
represented by the following general formula (G6) is preferable in
terms of yield in synthesis.
##STR00009##
[0029] In the formula, R.sup.7 and R.sup.8 represent an alkyl group
having 1 to 4 carbon atoms; and M is a central metal and represents
an element belonging to Group 9 or Group 10 in the periodic
table.
[0030] Here, as the organometallic complex having the structure
represented by the general formula (G1), more specifically, an
organometallic complex represented by the following general formula
(G7) is preferable since it can be easily synthesized.
##STR00010##
[0031] In the formula, Ar represents an arylene group; R represents
an alkoxy group having 1 to 4 carbon atoms; R.sup.1 and R.sup.2
individually represent hydrogen or an alkyl group having 1 to 4
carbon atoms; M is a central metal and represents an element
belonging to Group 9 or Group 10 in the periodic table; L
represents a monoanionic ligand; and n is 2 when the M is an
element belonging to Group 9, and n is 1 when the M is an element
belonging to Group 10.
[0032] As the organometallic complex having the structure
represented by the above general formula (G2), an organometallic
complex represented by the following general formula (G8) is
specifically preferable because it can be easily synthesized.
##STR00011##
[0033] In the formula, Ar represents an arylene group; R represents
an alkoxy group having 1 to 4 carbon atoms; R.sup.1 represents
hydrogen or an alkyl group having 1 to 4 carbon atoms; M is a
central metal and represents an element belonging to Group 9 or
Group 10 in the periodic table; L represents a monoanionic ligand;
and n is 2 when the M is an element belonging to Group 9, and n is
1 when the M is an element belonging to Group 10.
[0034] In addition, in the above general formula (G7), preferably,
R.sup.2 and R.sup.1 are hydrogen and an alkyl group, respectively,
in terms of yield in synthesis of the organometallic complex.
Therefore, a preferred structure of the present invention is an
organometallic complex represented by the following general formula
(G8).
##STR00012##
[0035] In the formula, Ar represents an arylene group; R represents
an alkoxy group having 1 to 4 carbon atoms; R.sup.1 represents an
alkyl group having 1 to 4 carbon atoms; M is a central metal and
represents an element belonging to Group 9 or Group 10 in the
periodic table; L represents a monoanionic ligand; and n is 2 when
the M is an element belonging to Group 9, and n is 1 when the M is
an element belonging to Group 10.
[0036] In addition, in the organometallic complex represented by
the above general formula (G8), a phenylene group is preferable for
the arylene group (Ar). By introducing a substituent to the
phenylene group, emission color with wide region of green color to
red color can be realized. Accordingly, a preferred structure of
the present invention is an organometallic complex represented by
the following general formula (G9).
##STR00013##
[0037] In the formula, R represents an alkoxy group having 1 to 4
carbon atoms; R.sup.1 represents an alkyl group having 1 to 4
carbon atoms; R.sup.3 to R.sup.6 individually represent hydrogen,
an alkyl group, an alkoxy group, a halogen group, a haloalkyl
group, an aryl group, a dialkylamino group, or a diarylamino group;
M is a central metal and represents an element belonging to Group 9
or Group 10 in the periodic table; L represents a monoanionic
ligand; and n is 2 when the M is an element belonging to Group 9,
and n is 1 when the M is an element belonging to Group 10.
[0038] Note that, in the organometallic complex represented by the
above general formula (G8), conjugation of the arylene group (Ar)
is expanded to obtain red emission color, which is useful.
Accordingly, a preferred structure of the present invention is an
organometallic complex including a structure represented by the
following general formula (G10).
##STR00014##
[0039] In the formula, R represents an alkoxy group having 1 to 4
carbon atoms; R.sup.1 represents an alkyl group having 1 to 4
carbon atoms; R.sup.7 and R.sup.8 represent an alkyl group; M is a
central metal and represents an element belonging to Group 9 or
Group 10 in the periodic table; L represents a monoanionic ligand;
and n is 2 when the M is an element belonging to Group 9, and n is
1 when the M is an element belonging to Group 10.
[0040] As the organometallic complex having the structure
represented by the above general formula (G9), an organometallic
complex represented by the following general formula (G11) is
specifically preferable in terms of yield in synthesis.
##STR00015##
[0041] In the formula, R.sup.3 to R.sup.6 individually represent
hydrogen, an alkyl group, an alkoxy group, a halogen group, a
haloalkyl group, an aryl group, a dialkylamino group, or a
diarylamino group; M is a central metal and represents an element
belonging to Group 9 or Group 10 in the periodic table; L
represents a monoanionic ligand; and n is 2 when the M is an
element belonging to Group 9, and n is 1 when the M is an element
belonging to Group 10.
[0042] Further, as the organometallic complex represented by the
above general formula (G10), more specifically, an organometallic
complex represented by the following general formula (G12) is
preferable in terms of yield in synthesis.
##STR00016##
[0043] In the formula, R.sup.7 and R.sup.8 represent an alkyl group
having 1 to 4 carbon atoms; M is a central metal and represents an
element belonging to Group 9 or Group 10 in the periodic table; L
represents a monoanionic ligand; and n is 2 when the M is an
element belonging to Group 9, and n is 1 when the M is an element
belonging to Group 10. The above-mentioned monoanionic ligand L is
preferably either a monoanionic bidentate chelate ligand having a
.beta.-diketone structure, a monoanionic bidentate chelate ligand
having a carboxyl group, a monoanionic bidentate chelate ligand
having a phenolic hydroxyl group, or a monoanionic bidentate
chelate ligand in which two ligand elements are both nitrogen. More
preferably, the monoanionic ligand L is a monoanionic ligand
represented by the following structural formulae (L1) to (L8).
Since these ligands have high coordinative ability and can be
obtained at low price, they are useful.
##STR00017##
[0044] For more efficient emission of phosphorescence, a heavy
metal is preferable as a central metal in terms of a heavy atom
effect. Therefore, one feature of the present invention is that
iridium or platinum is employed as the central metal M in the above
organometallic complexes of the present invention.
[0045] In the organometallic complexes having the structure
represented by the above general formulae (G1) to (G6) (in other
words, including the organometallic complexes represented by the
above general formulae (G7) to (G12)), the coordinate structure in
which the pyrazine derivative represented by the general formula
(G0) is ortho-metallated with a metal ion, contributes emission of
phosphorescence greatly. Thus, the above organometallic complexes
can be preferably used as a light-emitting material. In addition, a
light-emitting element formed using the organometallic complex has
a sharp emission spectrum, and thus its color purity is excellent.
Therefore, an organometallic complex of the present invention is
effective as a light-emitting material. Therefore, another
structure of the present invention is a light-emitting material
including such an organometallic complex as described above.
[0046] In addition, the organometallic complex of the present
invention can emit phosphorescence. In other words, a triplet
excited energy can be converted into light, and thus high
efficiency can be obtained by applying the organometallic complex
to a light-emitting element. Thus, the organometallic complex of
the present invention is very effective. In addition, by using an
organometallic complex of the present invention for a
light-emitting element, the light-emitting element can have a sharp
emission spectrum and can light emission with high color purity.
Therefore, the present invention also includes a light-emitting
element using an organometallic complex of the present
invention.
[0047] At this time, the organometallic complex of the present
invention is effective when it is used for a light-emitting
substance in terms of emission efficiency. Therefore, one feature
of the present invention is a light-emitting element using the
organometallic complex of the present invention as a light-emitting
substance.
[0048] The thus obtained light-emitting element of the present
invention can realize high light emission efficiency, and thus a
light-emitting device (such as an image display device or a
light-emitting device) using this light-emitting element can
realize low power consumption. Further, since the light-emitting
element has high color purity, a light-emitting device using the
light-emitting element (e.g., an image display device or a
light-emitting device) can provide high-quality image. Accordingly,
the present invention includes a light-emitting device, an
electronic device, and the like using the light-emitting element of
the present invention.
[0049] In this specification, the term "light-emitting device"
refers to an image display device or a light-emitting device
including a light-emitting element. Further, the category of the
light-emitting device includes a module including a light-emitting
element attached with a connector such as a module attached with an
anisotropic conductive film, TAB (Tape Automated Bonding) tape, or
a TCP (Tape Carrier Package); a module in which the top of the TAB
tape or the TCP is provided with a printed wiring board; or a
module in which an IC (Integrated Circuit) is directly mounted on a
light-emitting element by COG (Chip On Glass); and the like.
Further, the category includes a light-emitting device used for an
illumination apparatus and the like.
[0050] By carrying out the present invention, a wider variety of
organometallic complexes that can emit phosphorescence, in
particular, a wider variety of organometallic complexes, with which
a light-emitting element having a sharp emission spectrum can be
formed, can be provided. Moreover, an organometallic complex having
high emission efficiency can be provided.
[0051] Further, by forming a light-emitting element using an
organometallic complex of the present invention, a light-emitting
element having high color purity can be provided. Further, a
light-emitting element having a wider variation of emission color
from green to red can be provided. Moreover, a light-emitting
element having high emission efficiency can be provided.
[0052] By using organometallic complexes of the present invention,
light-emitting devices and electronic devices that can provide
high-quality images can be provided. Moreover, it is another object
of the present invention to provide light-emitting devices and
electronic devices with reduced power consumption.
BRIEF DESCRIPTION OF DRAWINGS
[0053] FIG. 1 illustrates a structure of a light-emitting element
using an organometallic complex according to an aspect of the
present invention;
[0054] FIG. 2 illustrates a structure of a light-emitting element
using an organometallic complex according to an aspect of the
present invention;
[0055] FIG. 3 illustrates a structure of a light-emitting element
using an organometallic complex according to an aspect of the
present invention;
[0056] FIGS. 4A to 4C each illustrate a light-emitting device using
a light-emitting element according to an aspect of the present
invention;
[0057] FIGS. 5A to 5C each illustrate an electronic device using a
light-emitting device of the present invention;
[0058] FIG. 6 is a .sup.1H-NMR chart of an organometallic complex,
[Ir(MOFppr-Me).sub.2(acac)], according to an aspect of the present
invention;
[0059] FIG. 7 is a graph showing an ultraviolet-visible absorption
spectrum and an emission spectrum of the organometallic complex
[Ir(MOFppr-Me).sub.2(acac)], according to an aspect of the present
invention;
[0060] FIG. 8 is a graph showing an emission efficiency of a
light-emitting element using the organometallic complex
[Ir(MOFppr-Me).sub.2(acac)], according to an aspect of the present
invention;
[0061] FIG. 9 is a graph showing an NTSC chromaticity coordinate of
the light-emitting element using the organometallic complex
[Ir(MOFppr-Me).sub.2(acac)], according to an aspect of the present
invention;
[0062] FIG. 10 is a graph showing an emission spectrum of the
light-emitting element using the organometallic complex
[Ir(MOFppr-Me).sub.2(acac)], according to an aspect of the present
invention;
[0063] FIG. 11 is a graph showing current density-luminance
characteristics of the light-emitting element using the
organometallic complex [Ir(MOFppr-Me).sub.2(acac)], according to an
aspect of the present invention;
[0064] FIG. 12 is a graph showing voltage-luminance characteristics
of the light-emitting element using the organometallic complex
[Ir(MOFppr-Me).sub.2(acac)], according to an aspect of the present
invention;
[0065] FIG. 13 is a graph showing voltage-current characteristics
of the light-emitting element using the organometallic complex
[Ir(MOFppr-Me).sub.2(acac)], according to an aspect of the present
invention;
[0066] FIG. 14 is a graph showing luminance-power efficiency
characteristics of the light-emitting element using the
organometallic complex [Ir(MOFppr-Me).sub.2(acac)], according to an
aspect of the present invention;
[0067] FIG. 15 is a graph showing luminance-external quantum
efficiency characteristics of the light-emitting element using the
organometallic complex [Ir(MOFppr-Me).sub.2(acac)], according to an
aspect of the present invention;
[0068] FIG. 16 is a .sup.1H-NMR chart of an organometallic complex,
[Ir(MOppr-Me).sub.2(acac)], according to an aspect of the present
invention;
[0069] FIG. 17 is a graph showing an ultraviolet-visible absorption
spectrum and an emission spectrum of the organometallic complex
[Ir(MOppr-Me).sub.2(acac)], according to an aspect of the present
invention;
[0070] FIG. 18 is a schematic view showing an electronic device
according to an aspect of the present invention;
[0071] FIG. 19 is a schematic view showing an electronic device
according to an aspect of the present invention; and
[0072] FIG. 20 is a schematic view showing an electronic device
according to an aspect of the present invention.
BEST MODE FOR CARRYING OUT THE INVENTION
Embodiment Mode
[0073] Hereinafter, embodiment modes of the present invention will
be described in detail with reference to the accompanying drawings.
Note that the present invention is not limited to the following
description, and it is easily understood by those skilled in the
art that modes and details thereof can be modified in various ways
without departing from the spirit and the scope of the invention.
Therefore, it should be noted that the present invention should not
be interpreted as being limited to the description of embodiment
modes.
Embodiment Mode 1
[0074] Embodiment Mode 1 will describe an organometallic complex of
the present invention.
<<Synthesis Method of an Alkoxypyrazine Derivative
Represented by a General Formula (G0)>>
[0075] An organometallic complex of the present invention is formed
by ortho metalation of a 2-alkoxy-3-arylpyrazine derivative
represented by the following general formula (G0) with respect to
an ion of a metal belonging to Group 9 or Group 10.
##STR00018##
[0076] In the formula, Ar represents an aryl group. R represents an
alkoxy group having 1 to 4 carbon atoms, and R.sup.1 and R.sup.2
individually represent hydrogen or an alkyl group having 1 to 4
carbon atoms.
[0077] The 2-alkoxy-3-arylpyrazine derivative represented by the
general formula (G0) can be synthesized by the following simple
synthetic scheme. For example, as represented by the following
scheme (a), the 2-alkoxy-3-arylpyrazine derivative can be obtained
by reacting a chloropyrazine derivative (A1) with alkoxide (A2).
Alternatively, as shown in the following scheme (a'), a halide of
arene (A1') is lithiated with alkyllithium or the like, and is
reacted with an alkoxypyrazine derivative (A2'), thereby obtaining
the 2-alkoxy-3-arylpyrazine derivative. Alternatively, as shown in
the following scheme (a''), 2-alkoxy-3-arylpyrazine (A1'') is
reacted with lithiations (A2''-1) and (A2''-2) in R.sup.1 and
R.sup.2, whereby the 2-alkoxy-3-arylpyrazine derivative can be
obtained. X in the formula denotes a halogen element.
##STR00019##
[0078] Since various kinds of the above-described compounds (A1),
(A2), (A1'), (A2'), (A1''), (A2''-1), and (A2''-2) are available
commercially or can be synthesized, many kinds of the
alkoxypyrazine derivative represented by the above-described
general formula (G0) can be synthesized. Accordingly, the
organometallic complexes of the present invention have wider
variations of ligands.
<<Synthesis Method of an Organometallic Compound of the
Present Invention Having a Structure Represented by a General
Formula (G1)>>
[0079] Next, an organometallic complex of the present invention
which is formed by ortho metalation of the 2-alkoxy-3-arylpyrazine
derivative represented by (G0), i.e., an organometallic complex
having the structure represented by the following general formula
(G1) will be described.
##STR00020##
[0080] In the formula, Ar represents an arylene group. R represent
an alkoxy group having 1 to 4 carbon atoms. R.sup.1 and R.sup.2
individually represent hydrogen or an alkyl group having 1 to 4
carbon atoms. M is a central metal and represents either an element
belonging to Group 9 or an element belonging to Group 10.
[0081] First, as represented by the following synthesis scheme (b),
2-alkoxy-3-arylpyrazine derivative represented by the general
formula (G0) and a compound of metal belonging to Group 9 or Group
10 and including halogen (a metal halide or a metal complex) is
heated with an alcohol solvent (such as glycerol, ethyleneglycol,
2-methoxyethanol, or 2-ethoxyethanol) alone or a mixed solvent of
one kind or more of such alcohol solvents and water, so that a
binuclear complex (B), which is a kind of organometallic complexes
of the present invention having the structure represented by the
general formula (G1), can be obtained. As a compound including a
metal belonging to Group 9 or Group 10 and including halogen, there
are given rhodium chloride hydrate, palladium chloride, iridium
chloride hydrate, iridium chloride hydrochloride hydrate, potassium
tetrachloroplatinate(II), and the like; however, the present
invention is not limited to these examples. In the scheme (b), M
denotes an element belonging to Group 9 or Group 10, and X denotes
a halogen element. In addition, n is 2 when M is an element
belonging to Group 9, and n is 1 when M is an element belonging to
Group 10.
##STR00021##
[0082] Further, as shown by the following synthesis scheme (c'),
the binuclear complex (B) and the 2-alkoxy-3-arylpyrazine
derivative represented by the general formula (G0) are heated at a
high temperature of about 200.degree. C. in a high boiling solvent
of glycerol or the like, and thus one type (C') of organometallic
complexs of the present invention including the structure
represented by the general formula (G1) can be obtained. As shown
in the synthesis scheme (c''), a binuclear complex (B) and a
compound which can be ortho-metallated, such as phenylpyridine
(more typically, a compound which can be cyclo-metallated) are
heated at a high temperature of around 200.degree. C. in a high
boilingsolvent of glycerol or the like, and thus, one type (C'') of
organometallic complexes of the present invention including the
structure represented by the general formula (G1) can be obtained.
In the schemes (c') and (c''), M denotes an element belonging to
Group 9 or Group 10, and X denotes a halogen element. In addition,
n is 2 when M is an element belonging to Group 9, and n is 1 when M
is an element belonging to Group 10.
##STR00022##
<<A Synthesis Method of an Organometallic Complex Represented
by a General Formula (G7)>
[0083] A preferable example, i.e., an organometallic complex
represented by the general formula (G7), among organometallic
complexes having the structure represented by the above general
formula (G1), will be described.
##STR00023##
[0084] In the formula, Ar represents an arylene group. R represents
an alkoxy group having 1 to 4 carbon atoms. R.sup.1 and R.sup.2
individually represent either hydrogen or an alkyl group having 1
to 4 carbon atoms. M is a central metal and represents either an
element belonging to Group 9 or an element belonging to Group 10. L
represents a monoanionic ligand. In addition, n is 2 when M is an
element belonging to Group 9, and n is 1 when M is an element
belonging to Group 10.
[0085] The organometallic complex of the present invention
represented by the above general formula (G7) can be synthesized by
the following scheme (c). In other words, the binuclear complex (B)
obtained by the above scheme (b) is reacted with a material HL of a
monoanionic ligand, and a proton of HL is eliminated and
coordinated to the central metal M. In this manner, the
organometallic complex of the present invention represented by the
general formula (G7) can be obtained. In the scheme (c), M denotes
an element belonging to Group 9 or Group 10, and X denotes a
halogen element. In addition, n is 2 when M is an element belonging
to Group 9, and n is 1 when M is an element belonging to Group
10.
##STR00024##
<<An Organometallic Complex of the Present Invention
Represented by the General Formula (G1), and a Specific Structural
Formula of an Organometallic Complex of the Present Invention which
is Represented by the General Formula (G7)>>
[0086] Then, specific structural formulae of the organometallic
complex of the present invention having the structure shown by the
general formula (G1), and the organometallic complex of the present
invention represented by the general formula (G7) will be
described.
[0087] The central metal M is selected from elements belonging to
Group 9 or Group 10; however, iridium(III) or platinum(II) is
preferable in terms of emission efficiency. In particular,
iridium(III) is preferably used, since it is thermally stable. In
addition, as specific examples of R in the formula (G1) or (G7), an
alkyl group such as a methyl group, an ethyl group, an isopropyl
group, or an n-butyl group can be given. By adopting such a
substituent to R, a synthesis yield of an organometallic complex
can be more enhanced than when R is hydrogen. As compared with when
a conjugated group (such as a phenyl group) is used for R, emission
spectrum of a light-emitting element formed using the
organometallic complex can be more sharpened, and thus color purity
can be increased.
[0088] As specific examples of R.sup.1 and R.sup.2, an alkyl group
typified by a methyl group, an ethyl group, an isopropyl group, an
n-butyl group or the like can be used as well as hydrogen.
[0089] As specific examples of Ar, a phenylene group, a phenylene
group in which at least one hydrogen is substituted by an alkyl
group such as a methyl group, a phenylene group in which at least
one hydrogen is substituted by an alkoxy group such as a methoxy
group, a phenylene group in which at least one hydrogen is
substituted by a hologen group such as a fluoro group, a phenylene
group in which at least one hydrogen is substituted by a
trifluoromethyl group, a phenylene group in which at least one
hydrogen is substituted by a phenyl group, a phenylene group in
which at least one hydrogen is substituted by a dialkylamino group
such as a dimethylamino group, a phenylene group in which at least
one hydrogen is substituted by a diarylamino group such as a
diphenylamino group are given. In particular, by using a phenylene
group in which at least one hydrogen is substituted by a halogen
group or a trifluoromethyl group for Ar, emission wavelength can be
shifted to a shorter wavelength than when an unsubstituted
phenylene group is used for Ar. By using a phenylene group
substituted by a dialkylamino group or a diarylamino group for Ar,
emission wavelength can be shifted to a longer wavelength than when
an unsubstituted phenylene group is used for Ar. Further, as Ar,
9,9-dimethylfluorene-diyl group such as 9,9-dialkylfluorene-diyl
can be applied. In that case, emission wavelength can be shifted to
a longer wavelength side than when Ar adopts an unsubstituted
phenylene group.
[0090] Next, the monoanionic ligand L in the above general formula
(G7) is described. The monoanionic ligand L is preferably any one
of a monoanionic bidentate chelate ligand having a .beta.-diketone
structure, a monoanionic bidentate chelate ligand having a carboxyl
group, a monoanionic bidentate chelate ligand having a phenolic
hydroxyl group, and a monoanionic bidentate chelate ligand in which
two ligand elements are both nitrogen, because these ligands have
high coordinating ability. More specifically, monoanionic ligands
represented by the following structural formulae (L1) to (L8) are
given. However, the monoanionic ligand L is not limited to these
examples.
##STR00025##
[0091] By using the central metal M, the substituents R, R.sup.1
and Ar, the monoanionic ligand L as described above in combination
as appropriate an organometallic complex of the present invention
is constituted. Hereinafter, specific structural formulae (1) to
(47) of organometallic complexes of the present invention are
given. Note that the present invention is not limited thereto.
##STR00026## ##STR00027## ##STR00028## ##STR00029## ##STR00030##
##STR00031## ##STR00032## ##STR00033## ##STR00034## ##STR00035##
##STR00036## ##STR00037##
[0092] In the organometallic complexes represented by the above
structural formulae (1) to (47), there can be a geometrical isomer
and a stereoisomer according to the type of ligand. The
organometallic complex of the present invention includes such
isomers. In addition, there are two geometrical isomers of a facial
isomer and a meridional isomer as the organometallic complex
represented by the structural formulae (10), (21) and (32). The
organometallic complex of the present invention includes both
isomers.
[0093] The foregoing organometallic complex of the present
invention can be used as a photosensitizer owing to capability of
intersystem crossing. Further, it can exhibit phosphorescence.
Thus, the organometallic complexes of the present invention can
each be used as a light-emitting material or a light-emitting
substance for a light-emitting element.
Embodiment Mode 2
[0094] Embodiment Mode 2 will describe a mode of a light-emitting
element which has the organometallic complex of the present
invention described in Embodiment Mode 1, as a light-emitting
substance with reference to FIG. 1.
[0095] FIG. 1 is a view showing a light-emitting element including
a light-emitting layer 113 between a first electrode 101 and a
second electrode 102. The light-emitting layer 113 includes such an
organometallic complex of the present invention as described in
Embodiment Mode 1.
[0096] By applying a voltage to such a light-emitting element,
holes injected from the first electrode 101 side and electrons
injected from the second electrode 102 side recombine with each
other in the light-emitting layer 113 to bring the organometallic
complex of the present invention to an excited state. When the
organometallic complex in the excited state returns to the ground
state, it emits light. As thus described, the organometallic
complex of the present invention functions as a light-emitting
substance of the light-emitting element, It is to be noted that, in
the light-emitting element of the present Embodiment Mode 2, the
first electrode 101 functions as an anode and the second electrode
102 functions as a cathode.
[0097] Here, the light-emitting layer 113 includes an
organometallic complex of the present invention. The light-emitting
layer 113 preferably includes, as a host, a substance which has a
larger triplet excitation energy than that of the organometallic
complex of the present invention and also includes, as a guest, the
organometallic complex of the present invention, which is
dispersedly contained. Thus, quenching of light emitted from the
organometallic complex of the present invention caused depending on
the concentration can be prevented. It is to be noted that the
triplet excitation energy indicates an energy gap between a ground
state and a triplet excited state.
[0098] There are no particular limitations on substances used to
disperse an organometallic complex of the present invention (i.e.,
host). Specifically, an aromatic amine compound such as
4,4'-bis[N-(1-naphtyl)-N-phenylamino]biphenyl (abbreviation: NPB),
4,4'-bis[N-(9-phenanthryl)-N-phenylamino]biphenyl (abbreviation:
PPB), 4,4'-bis[N-(3-methylphenyl)-N-phenylamino]biphenyl
(abbreviation: TPD),
4,4'-bis[N-(9,9-dimethylfluoren-2-yl)-N-phenylamino]biphenyl
(abbreviation: DFLDPBi),
4,4',4''-tris(N,N-diphenylamino)triphenylamine (abbreviation:
TDATA),
4,4',4''-tris[N-(3-methylphenyl)-N-phenylamino]triphenylamine
(abbreviation: m-MTDATA), 4,4',4''-tri(N-carbazolyl)triphenylamine
(abbreviation: TCTA), 1,1-bis[4-(diphenylamino)phenyl]cyclohexane
(abbreviation: TPAC), 9,9-bis[4-(diphenylamino)phenyl]fluorene
(abbreviation: TPAF),
4-(9H-carbazolyl)-4'-(5-phenyl-1,3,4-oxadiazol-2-yl)triphenylamine
(abbreviation: YGAO11), or
N-[4-(9-carbazolyl)phenyl]-N-phenyl-9,9-dimethylfluoren-2-amine
(abbreviation: YGAF) can be used. Also, a carbazole derivative such
as 4,4'-di(N-carbazolyl)biphenyl (abbreviation: CBP),
1,3-bis(N-carbazolyl)benzene (abbreviation: mCP), or
1,3,5-tris(N-carbazolyl)benzene (abbreviation: TCzB) can be used.
Further, a high molecular compound such as
poly(4-vinyltriphenylamine) (abbreviation: PVTPA) can also be used
as such an aromatic amine compound. As a carbazole derivative, a
high molecular compound such as poly(N-vinylcarbazole)
(abbreviation: PVK) can also be used. The triplet excitation energy
of the substance serving as a host as described above is preferably
larger than that of the pyrazine-based organometallic complex of
the present invention.
[0099] A light-emitting element formed using the organometallic
complex of the present invention has a sharp emission spectrum, and
thus the light-emitting element has high color purity. Since the
organometallic complex of the present invention has enriched
variation of emission color of green light to red light, a
light-emitting element which can emit various light of green to
red, can be provided. Furthermore, since the organometallic complex
of the present invention has high emission efficiency of
phosphorescence, a light-emitting element with high emission
efficiency can be provided.
[0100] Although there is no particular limitation on the first
electrode 101, the first electrode 101 is preferably formed by
using a substance which has a high work function when the first
electrode 101 functions as an anode as in Embodiment Mode 2.
Specifically, gold (Au), platinum (Pt), nickel (Ni), tungsten (W),
chromium (Cr), molybdenum (Mo), iron (Fe), cobalt (Co), copper
(Cu), palladium (Pd), and the like can be used in addition to
indium tin oxide (ITO), indium tin oxide containing silicon oxide
(ITSO), indium oxide containing 2 to 20 wt % zinc oxide (IZO). The
first electrode 101 can be formed by, for example, a sputtering
method, an evaporation method, or the like.
[0101] There is no particular limitation on a material for the
second electrode 102. However, when the second electrode 102
functions as a cathode as in Embodiment Mode 2, a substance having
a low work function is preferably used. Specifically, in addition
to aluminum (Al) or indium (In), an alkali metal such as lithium
(Li) or cesium (Cs); an alkali-earth metal such as magnesium (Mg)
or calcium (Ca); a rare-earth metal such as erbium (Er) or
ytterbium (Yb) or the like can be used. In addition, an alloy such
as aluminum-lithium alloy (AlLi) or magnesium-silver alloy (MgAg)
can also be used. The second electrode 102 can be formed by, for
example, sputtering, evaporation, or the like.
[0102] Note that a conductive composition including a conductive
high molecular compound (also referred to as a conductive polymer)
can be used for the first electrode 101 and the second electrode
102. When a thin film of a conductive composition is formed as each
of the first electrode 101 and the second electrode 102, the thin
film preferably has sheet resistance of equal to or less than 10000
.OMEGA./square and light transmittance of equal to or higher than
70% at a wavelength of 550 nm. Note that resistance of a conductive
high molecule which is included in the thin film is preferably
equal to or lower than 0.1 .OMEGA.cm.
[0103] As a conductive high molecule, so-called .pi. electron
conjugated high molecule can be used. For example, polyaniline
and/or a derivative thereof, polypyrrole and/or a derivative
thereof, polythiophene and/or a derivative thereof, and a copolymer
of two or more kinds of those materials can be given.
[0104] Specific examples of a conjugated conductive high-molecule
are given below: polypyrrole, poly(3-methylpyrrole),
poly(3-butylpyrrole), poly(3-octylpyrrole), poly(3-decylpyrrole),
poly(3,4-dimethylpyrrole), poly(3,4-dibutylpyrrole),
poly(3-hydroxypyrrole), poly(3-methyl-4-hydroxypyrrole),
poly(3-methoxypyrrole), poly(3-ethoxypyrrole),
poly(3-octoxypyrrole), poly(3-carboxylpyrrole),
poly(3-methyl-4-carboxylpyrrole), polyN-methylpyrrole,
polythiophene, poly(3-methylthiophene), poly(3-butylthiophene),
poly(3-octylthiophene), poly(3-decylthiophene),
poly(3-dodecylthiophene), poly(3-methoxythiophene),
poly(3-ethoxythiophene), poly(3-octoxythiophene),
poly(3-carboxylthiophene), poly(3-methyl-4-carboxylthiophene),
poly(3,4-ethylenedioxythiophene), polyaniline,
poly(2-methylaniline), poly(2-octylaniline),
poly(2-isobutylaniline), poly(3-isobutylaniline),
poly(2-anilinesulfonic acid), or poly(3-anilinesulfonic acid).
[0105] One of the above-described conductive high molecular
compounds can be used alone for the first electrode 101 or the
second electrode 102, or an organic resin is added to such a
conductive high molecular compound in order to adjust film
characteristics such that it can be used as a conductive
composition.
[0106] As for an organic resin, a thermosetting resin, a
thermoplastic resin, or a photocurable resin may be used, as long
as such a resin is compatible to a conductive high molecule or a
resin can be mixed and dispersed into a conductive high molecule.
For example, a polyester-based resin such as polyethylene
terephthalate, polybutylene terephthalate, or polyethylene
naphthalate; a polyimide-based resin such as polyimide or polyimide
amide; a polyamide resin such as polyamide 6, polyamide 6,6,
polyamide 12, or polyamide 11; a fluorine resin such as
poly(vinylidene fluoride), polyvinyl fluoride,
polytetrafluoroethylene, ethylene tetrafluoroethylene copolymer, or
polychlorotrifluoroethylene; a vinyl resin such as polyvinyl
alcohol, polyvinyl ether, polyvinyl butyral, polyvinyl acetate, or
polyvinyl chloride; an epoxy resin; a xylene resin; an aramid
resin; a polyurethane-based resin; a polyurea-based resin, a
melamine resin; a phenol-based resin; polyether; an acrylic-based
resin, or a copolymer of any of those resins can be given.
[0107] Further, the conductive high molecule or conductive
composition may be doped with an acceptor dopant or a donor dopant
so that oxidation-reduction potential of a conjugated electron in
the conductive high-molecule or the conductive composition may be
changed in order to adjust conductivity of the conductive high
molecule or conductive composition.
[0108] As an acceptor dopant, a halogen compound, an organic cyano
compound, an organic metal compound, or the like can be used.
Examples of a halogen compound are chlorine, bromine, iodine,
iodine chloride, iodine bromide, iodine fluoride, and the like.
Lewis acid such as phosphorus pentafluoride, arsenic pentafluoride,
antimony pentafluoride, boron trifluoride, boron trichloride, and
boron tribromide; proton acid such as inorganic acid such as
hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid,
fluoroboric acid, hydrofluoric acid, and perchloric acid and
organic acid such as organic carboxylic acid and organic sulfonic
acid can be used. As the organic carboxylic acid and the organic
sulfonic acid, the above-described carboxylic acid compounds or
sulfonic acid compounds can be used. As the organic cyano compound,
a compound in which two or more cyano groups are included in a
conjugated bond can be used. For example, there are
tetracyanoethylene, tetracyano ethylene oxide, totracyanobenzene,
tetracyanoquinodimethane, tetracyano azanaphthalene, and the
like.
[0109] As the donor dopant, there are alkali metal, alkaline-earth
metal, a quaternary amine compound, and the like.
[0110] Further, a thin film used for the first electrode 101 or the
second electrode 102 can be formed by a wet process using a
solution in which the conductive high molecule or the conductive
composition is dissolved in water or an organic solvent (e.g., an
alcohol solvent, a ketone solvent, an ester solvent, a hydrocarbon
solvent, or an aromatic solvent).
[0111] There is no particular limitation on the solvent in which
the conductive high molecule or the conductive composition is
dissolved as long as the above-described conductive high molecule
and the high molecular resin compound such as an organic resin are
dissolved. For example, the conductive composition may be dissolved
in a single solvent or a mixed solvent of the following: water,
methanol, ethanol, propylene carbonate, N-methylpyrrolidone,
dimethylformamide, dimethylacetamide, cyclohexanone, acetone,
methyletylketone, methylisobutylketone, toluene, and/or the
like.
[0112] Formation of a film using a solution in which the conductive
high molecule or conductive composition is dissolved in a solvent
can be performed by a wet process, such as an application method, a
coating method, a droplet discharge method (also referred to as an
inkjet method), or a printing method. The solvent may dried with
thermal treatment or may be dried under reduced pressure. In the
case where the organic resin is a thermosetting resin, heat
treatment may be performed further. In the case where the organic
resin is a photocurable resin, light irradiation treatment may be
performed.
[0113] In order to extract emitted light to the outside, it is
preferable that one or both of the first electrode 101 and the
second electrode 102 be an electrode formed using a conductive film
through which visible light is transmitted, such as ITO, or an
electrode formed with a thickness of several to several tens of nm
such that visible light can be transmitted.
[0114] In addition, a hole-transporting layer 112 may be provided
between the first electrode 101 and the light-emitting layer 113 as
shown in FIG. 1. Here, the hole-transporting layer is a layer that
has a function of transporting holes injected from the first
electrode 101 to the light-emitting layer 113. The
hole-transporting layer 112 is provided to keep the first electrode
101 away from the light-emitting layer 113 in this way; thus,
quenching of light due to a metal can be prevented. However, the
hole-transporting layer 112 is not necessarily provided.
[0115] There is no particular limitation on the substance for
forming the hole-transporting layer 112. Specifically, an aromatic
amine compound such as
4,4'-bis[N-(1-napthyl)-N-phenylamino]biphenyl (abbreviation: NPB),
4,4'-bis[N-(9-phenanthryl)-N-phenylamino]biphenyl (abbreviation:
PPB), 4,4'-bis[N-(3-methylphenyl)-N-phenylamino]biphenyl
(abbreviation: TPD),
4,4'-bis[N-(9,9-dimethylfluoren-2-yl)-N-phenylamino]biphenyl
(abbreviation: DFLDPBi),
4,4',4''-tris(N,N-diphenylamino)triphenylamine (abbreviation:
TDATA),
4,4',4''-tris[N-(3-methylphenyl)-N-phenylamino]triphenylamine
(abbreviation: m-MTDATA), 4,4',4''-tri(N-carbazolyl)triphenylamine
(abbreviation: TCTA), 1,1-bis[4-(diphenylamino)phenyl]cyclohexane
(abbreviation: TPAC), 9,9-bis[4-(diphenylamino)phenyl]fluorene
(abbreviation: TPAF),
4-(9-carbazolyl)-4'-(5-phenyl-1,3,4-oxadiazol-2-yl)triphenylamine
(abbreviation: YGAO11), or
N-[4-(9-carbazolyl)phenyl]-N-phenyl-9,9-dimethylfluoren-2-amine
(abbreviation: YGAF) can be used. Also, a carbazole derivative such
as 4,4'-di(N-carbazolyl)biphenyl (abbreviation: CBP),
1,3-bis(N-carbazolyl)benzene (abbreviation: mCP), or
1,3,5-tris(N-carbazolyl)benzene (abbreviation: TCzB) can be used.
Further, a high molecular compound such as
poly(4-vinyltriphenylamine) (abbreviation: PVTPA) can also be used
as such an aromatic amine compound. As a carbazole derivative, a
high molecular compound such as poly(N-vinylcarbazole)
(abbreviation: PVK) can also be used. The triplet excitation energy
of the substance used for the hole-transporting layer 112 is
preferably larger than that of the pyrazine-based organometallic
complex.
[0116] It is to be noted that the hole-transporting layer 112 may
have a multilayer structure formed of two or more layers stacked
together. In addition, the hole-transporting layer 112 may also be
formed by mixing two or more types of substances.
[0117] Moreover, an electron-transporting layer 114 may be provided
between the second electrode 102 and the light-emitting layer 113
as shown in FIG. 1. Here, the electron-transporting layer is a
layer which has a function of transporting electrons injected from
the second electrode 102 to the light-emitting layer 113. In such a
manner, the electron-transporting layer 114 is provided to separate
the second electrode 102 from the light-emitting layer 113, whereby
quenching of light-emission due to a metal can be prevented. Note
that the electron-transporting layer 114 is not always
necessary.
[0118] There is no particular limitation on a substance for forming
the electron-transporting layer 114. Specifically, a heteroaromatic
compound such as
9-[4-(5-phenyl-1,3,4-oxadiazol-2-yl)phenyl]carbazole (abbreviation:
CO11), 1,3-bis[5-(p-tert-buthylphenyl)-1,3,4-oxadiazol-2-yl]benzene
(abbreviation: OXD-7),
2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole
(abbreviation: PBD),
2,2',2''-(1,3,5-benzenetriyl)tris(1-phenyl-1H-benzimidazole)
(abbreviation: TPBI),
3-(4-tert-butylphenyl)-4-phenyl-5-(4-biphenylyl)-1,2,4-triazole
(abbreviation: TAZ),
3-(4-tert-butylphenyl)-4-(4-ethylphenyl)-5-(4-biphenylyl)-1,2,4-triazole
(abbreviation: p-EtTAZ),
9,9',9''-[1,3,5-triazine-2,4,6-triyl]tricarbazole (abbreviation:
TCzTRZ),
2,2',2''-(1,3,5-benzenetriyl)tris(6,7-dimethyl-3-phenylquinoxaline)
(abbreviation: TriMeQn),
9,9'-(quinoxaline-2,3-diydi-4,1-phenylene)di(9H-carbazole)
(abbreviation: CzQn),
3,3',6,6'-tetraphenyl-9,9'-(quinoxaline-2,3-diyldi-4,1phenylene)di-
(9H-carbazole) (abbreviation: DCzPQ), bathophenanthroline
(abbreviation: BPhen), or bathocuproine (abbreviation: BCP) can be
used. A metal complex such as is
bis(2-methyl-8-quinolinolato)(4-phenylphenolato)aluminum(III)
(abbreviation: BAlq),
tris[2-(2-hydroxyphenyl)-5-phenyl-1,3,4-oxadiazolato]aluminum(III)
(abbreviation: Al(OXD).sub.3),
tris(2-hydroxyphenyl-1-phenyl-1H-benzimidazolato)aluminum(III)
(abbreviation: Al(BIZ).sub.3),
bis[2-(2-hydroxyphenyl)benzothiazolato]zinc(II) (abbreviation:
Zn(BTZ).sub.2), or bis[2-(2-hydroxyphenyl)benzoxazolato]zinc(II)
(abbreviation: Zn(PBO).sub.2) can be used. Further, a high
molecular compound such as poly(2,5-pyridine-diyl) (abbreviation:
PPy) can also be used as such a heteroaromatic compound. As a metal
complex, metal complex high molecular compounds as disclosed as in
the following reference can also be used (TAO et al., C--H BOND
ACTIVATION BY A FERRIC METHOXIDE COMPLEX: MODELING THE
RATE-DETERMINING STEP IN THE MECHANISM OF LIPOXYGENASE, APPL. PHYS.
LETT. (APPLIED PHYSICS LETTERS, vol. 70, No. 12, 24 Mar. 1997,
pages 1503-1505.). Note that the triplet excitation energy of the
substance used for the electron-transporting layer 114 described
above is preferably larger than that of the pyrazine-based
organometallic complex.
[0119] Note that the electron-transporting layer 114 may have a
multilayer structure in which two or more layers are stacked. In
addition, the electron-transporting layer 114 may also be formed by
mixing two or more types of substances.
[0120] Further, a hole-injecting layer 111 may be provided between
the first electrode 101 and the hole-transporting layer 112 as
shown in FIG. 1. Here, the hole-injecting layer is a layer that has
a function of assisting injection of holes from an electrode
functioning as an anode to the hole-transporting layer 112. Note
that the hole-injecting layer 111 is not always necessary.
[0121] There is no particular limitation on the substance used for
the hole-injection layer 111; a metal oxide such as vanadium oxide,
niobium oxide, tantalum oxide, chromium oxide, molybdenum oxide,
tungsten oxide, manganese oxide, rhenium oxide, ruthenium oxide, or
the like can be used. In addition, a phthalocyanine compound such
as phthalocyanine (abbreviation: H.sub.2Pc), copper phthalocyanine
(abbreviation: CuPc), or the like can also be used. In addition,
the substances for forming the hole-transporting layer 112 as
described above can also be used. Further, a high molecular
compound such as a mixture of poly(ethylenedioxythiophene) and
poly(styrenesulfonic acid) (abbreviation: PEDOT/PSS) can also be
used.
[0122] A composite material of an organic compound and an electron
acceptor may be used for the hole-injecting layer 111. Such a
composite material is superior in a hole-injecting property and a
hole-transporting property since holes are generated in the organic
compound by the electron acceptor. In this case, the organic
compound is preferably a material excellent in transporting the
generated holes. Specifically, the above-described substances used
for the hole-transporting layer 112 (such as aromatic amine
compounds) can be used. As the electron acceptor, a substance
having an electron accepting property to the organic compound may
be used. Specifically, transition metal oxide is preferable and
examples thereof include vanadium oxide, niobium oxide, tantalum
oxide, chromium oxide, molybdenum oxide, tungsten oxide, manganese
oxide, rhenium oxide, ruthenium oxide, and the like. Lewis acid
such as iron(III) chloride or aluminum(III) chloride can also be
used. In addition, an organic compound such as
7,7,8,8-tetracyano-2,3,5,6-tetrafluoroquinodimethane (abbrev.:
F4-TCNQ) can also be used.
[0123] Note that the hole-injecting layer 111 may have a multilayer
structure in which two or more layers are stacked. In addition, the
hole-transporting layer 112 may also be formed by mixing two or
more types of substances.
[0124] In addition, as shown in FIG. 1, an electron-injecting layer
115 may be provided between the second electrode 102 and the
electron-transporting layer 114. Here, the electron-injecting layer
is a layer which has a function of assisting injection of electrons
from the electrode functioning as a cathode to the
electron-transporting layer 114. Note that the electron-injecting
layer 115 is not always necessary.
[0125] There is no particular limitation on the substance used for
the electron-injecting layer 115. An alkali metal compound or an
alkaline earth metal compound such as lithium fluoride, cesium
fluoride, calcium fluoride, or lithium oxide can be used. In
addition, a rare earth metal compound such as erbium fluoride can
also be used. In addition, the substance for the
electron-transporting layer 114 as described above can also be
used.
[0126] Alternatively, a composite material which is formed by
combining an organic compound and an electron donor may be used for
the electron-injecting layer 115. Such a composite material is
superior in an electron-injecting property and an
electron-transporting property since electrons are generated in the
organic compound by the electron donor. In this case, for the
organic compound, it is preferable that it be a material that
excels in the transportation of generated electrons; specifically,
any of the substances (the metal complexes, the heteroaromatic
compounds, and the like) given above that are used to form the
electron-transporting layer 114 can be used, for example. As the
electron donor, a substance showing an electron donating property
to the organic compound may be used. Specifically an alkali metal,
an alkali-earth metal or a rare earth metal is preferable, and for
example, lithium, cesium, magnesium, calcium, erbium, or ytterbium,
can be given. Further, alkali metal oxide or alkaline-earth metal
oxide is preferable, and for example, lithium oxide, calcium oxide,
barium oxide, or the like can be given. In addition, an alkali
metal compound or an alkaline earth metal compound such as lithium
oxide, calcium oxide, barium oxide, or cesium carbonate can be
used. Further, Lewis base such as magnesium oxide or an organic
compound such as tetrathiafulvalene (abbreviation: TTF) can also be
used.
[0127] In the foregoing light-emitting element of the present
invention, each of the hole-injecting layer 111, the
hole-transporting layer 112, the light-emitting layer 113, the
electron-transporting layer 114, and the electron-injecting layer
115 may be formed by any method, for example, an evaporation
method, an inkjet method, an application method, or the like. In
addition, the first electrode 101 or the second electrode 102 may
be formed by any method, for example, a sputtering method, an
evaporation method, an inkjet method, an application method, or the
like.
Embodiment Mode 3
[0128] A light-emitting element of the present invention may have a
plurality of light-emitting layers. For example, white light can be
obtained by providing a plurality of light-emitting layers and
mixing light emitted from each of the light-emitting layers.
Accordingly, white color light emission can be obtained for
example. In Embodiment Mode 3, a light-emitting element having a
plurality of light-emitting layers is described with reference to
FIG. 2.
[0129] In FIG. 2, a first light-emitting layer 213 and a second
light-emitting layer 215 are provided between a first electrode 201
and a second electrode 202. Mixed light of light emitted from the
first light-emitting layer 213 and light emitted from the second
light-emitting layer 215 can be obtained. A separation layer 214 is
preferably formed between the first light-emitting layer 213 and
the second light-emitting layer 215. When voltage is applied such
that the potential of the first electrode 201 is higher than the
potential of the second electrode 202, current flows between the
first electrode 201 and the second electrode 202, and holes and
electrons are recombined in the first light-emitting layer 213, the
second light-emitting layer 215, or the separation layer 214. The
generated excitation energy is distributed to the first
light-emitting layer 213 and the second light-emitting layer 215 to
bring each of a first light-emitting substance contained in the
first light-emitting layer 213 and a second light-emitting
substance contained in the second light-emitting layer 215 to an
excited state. The excited first and second light-emitting
substances emit light while returning to ground states.
[0130] The first light-emitting layer 213 contains the first
light-emitting substance typified by a fluorescent substance such
as perylene, 2,5,8,11-tetra(tert-butyl)perylene (abbreviation:
TBP), 4,4'-bis(2,2-diphenylvinyl)biphenyl (abbreviation: DPVBi),
4,4'-bis[2-(N-ethylcarbazol-3-yl)vinyl]biphenyl (abbreviation:
BCzVBi), bis(2-methyl-8-quinolinolato)(4-phenylphenolato)aluminum
(abbreviation: BAlq), or
bis(2-methyl-8-quinolinolato)galliumchloride (abbreviation:
Gamq.sub.2Cl), or a phosphorescent substance such as
bis{2-[3,5-bis(trifluoromethyl)phenyl]pyridinato-N,C.sup.2'}iridium(III)p-
icolinate (abbreviation: Ir(CF.sub.3ppy).sub.2(pic)),
bis[2-(4,6-difluorophenyl)pyridinato-N,C.sup.2']iridium(III)acetylacetona-
te (abbreviation: FIr(acac)),
bis[2-(4,6-difluorophenyl)pyridinato-N,C.sup.2']iridium(III)picolinate
(abbreviation: FIrpic), or
bis[2-(4,6-difuluorophenyl)pyridinato-N,C.sup.2 iridium(III)
tetra(1-pyrazolyl)borate (abbreviation: FIr6), from which light
emission with a peak between 450 nm and 510 nm in an emission
spectrum (i.e., blue light to blue green light) can be obtained. In
addition, when the first light-emitting substance is a fluorescent
compound, the first light-emitting layer 213 preferably has a
structure in which a substance having a larger singlet excited
energy than the first light-emitting substance is used as a first
host and the first light-emitting substance is dispersedly
contained as a guest. Further, when the first light-emitting
substance is a phosphorescent compound, the light-emitting layer
213 preferably has a structure in which a substance having a larger
triplet excited energy than the first light-emitting substance is
used as a first host and the first light-emitting substance is
dispersedly contained as a guest. As the first host,
9,10-di(2-naphthyl)anthracene (abbreviation: DNA),
2-tert-butyl-9,10-di(2-naphthyl)anthracene (abbreviation: t-BuDNA)
or the like can be used as well as NPB, CBP, TCTA or the like. It
is noted that the singlet exited energy is energy difference
between a ground state and a singlet excited state, and the triplet
exited energy is energy difference between a ground state and a
triplet excited state.
[0131] On the other hand, the second light-emitting layer 215
includes an organometallic complex of the present invention and can
exhibit light emission of green to red. The second light-emitting
layer 215 may have the same structure as the light-emitting layer
113 described in Embodiment Mode 2. In addition, the separation
layer 214 can be specifically formed of TPAQn, NPB, CBP, TCTA,
Znpp.sub.2, ZnBOX or the like described above. The separation layer
214 is provided in this manner, and therefore a defect that
emission intensity of only one of the first light-emitting layer
213 and the second light-emitting layer 215 is stronger than that
of the other thereof can be prevented. However, the separation
layer 214 is not necessarily provided, and it may be provided as
appropriate such that the ratio between emission intensities of the
first light-emitting layer 213 and the second light-emitting layer
215 can be adjusted.
[0132] In Embodiment Mode 3, an organometallic complex of the
present invention is used for the second light-emitting layer 215,
and another light-emitting substance is used for the first
light-emitting layer 213; however, the organometallic complex of
the present invention may be used for the first light-emitting
layer 213, and another light-emitting substance is used for the
second light-emitting layer 215.
[0133] In Embodiment Mode 3, a light-emitting element including two
light-emitting layers is described as shown in FIG. 2; however, the
number of the light-emitting layers is not limited to two, and may
be three, for example. Light emission from each light-emitting
layer may be mixed. As a result, white color emission can, for
example, be obtained.
[0134] It is to be noted that, the first electrode 201 may have the
same structure as the first electrode 101 described in the
preceding Embodiment Mode 2. In addition, the second electrode 202
may have a structure similar to the second electrode 102 described
in Embodiment Mode 2.
[0135] In Embodiment Mode 3, as shown in FIG. 2, the hole-injecting
layer 211, the hole-transporting layer 212, the
electron-transporting layer 216, and the electron-injecting layer
217 are provided; however, also to structures of these layers, the
structures of the respective layers described in Embodiment Mode 2
may be applied. However, these layers are not necessarily provided
and may be provided according to element characteristics.
Embodiment Mode 4
[0136] Embodiment Mode 4 exemplifies a light-emitting element which
includes a plurality of light-emitting layers, which has a
different element structure from that in Embodiment Mode 3, and in
which light is emitted from each light-emitting layer, Therefore,
also in Embodiment Mode 4, light which is the combination of a
plurality of light can be obtained. In other words, white color
light emission can be obtained, for example. Hereinafter,
description is made with reference to FIG. 3.
[0137] In the light-emitting element of FIG. 3, a first
light-emitting layer 313 and a second light-emitting layer 323 are
provided between a first electrode 301 and a second electrode 302.
An N layer 315 and a P layer 321 as charge generating layers are
provided between the first light-emitting layer 313 and the second
light-emitting layer 323.
[0138] The N layer 315 is a layer for generating electrons, and the
P layer 321 is a layer for generating holes. When a voltage is
applied such that the potential of the first electrode 301 is
higher than that of the second electrode 302, holes injected from
the first electrode 301 and electrons injected from the N layer 315
are recombined in the first light-emitting layer 313, and thus a
first light-emitting substance included in the first light-emitting
layer 313 emits light. Further, electrons injected from the second
electrode 302 and holes injected from the P layer 321 are
recombined in the second light-emitting layer 323, and thus a
second light-emitting substance included in the second
light-emitting layer 323 emits light.
[0139] The first light-emitting layer 313 may have the same
structure as the first light-emitting layer 213 in Embodiment Mode
3, and light with a peak of emission spectrum (i.e., blue light to
blue green light) between 450 nm and 510 nm can be emitted. The
second light-emitting layer 323 may have the same structure as the
second light-emitting layer 215 in Embodiment Mode 3, and includes
an organometallic complex of the present invention and green light
to red light can be obtained.
[0140] The N layer 315 is a layer for generating electrons and thus
may be formed using a composite material in which the organic
compound and the electron donor described in Embodiment Mode 2 are
combined. By adopting such a structure, electrons can be injected
to the first light-emitting 313 side.
[0141] Since the P layer 321 is a layer for generating holes, it
may be formed using a composite material in which the organic
compound and the electron donor described in Embodiment Mode 2 are
combined. By adopting such a structure, holes can be injected to
the second light-emitting 323 side. For the P layer 321, metal
oxide having an excellent hole-injecting property, such as
molybdenum oxide, vanadium oxide, ITO, or ITSO, can be used.
[0142] Here, Embodiment Mode 4 describes a light-emitting element
in which the two light-emitting layers are provided as shown in
FIG. 3; however, the number of light-emitting layers is not limited
to two. For example, three light-emitting layers may be provided.
Light emission from each light-emitting layer may be mixed. As a
result, white color emission can, for example, be obtained.
[0143] The first electrode 301 may have a similar structure to the
first electrode 101 of Embodiment Mode 2. In addition, the second
electrode 302 may have the same structure as the second electrode
102 described in Embodiment Mode 2.
[0144] In Embodiment Mode 4, as shown in FIG. 3, a hole-injecting
layer 311, hole-transporting layers 312 and 322,
electron-transporting layers 314 and 324, and an electron-injecting
layer 325 are provided. As to these layers, the structures of the
respective layers described in Embodiment Mode 2 may also be
applied. However, these layers are not necessarily provided and may
be provided according to element characteristics.
Embodiment Mode 5
[0145] Embodiment Mode 5 will describe a mode of a light-emitting
element using the organometallic complex of the present invention
as a sensitizer, with reference to FIG. 1.
[0146] FIG. 1 shows a light-emitting element including a
light-emitting layer 113 between a first electrode 101 and a second
electrode 102. The light-emitting layer 113 contains such an
organometallic complex of the present invention as described in
Embodiment Mode 1, and a fluorescent compound which can emit light
with a longer wavelength than the organometallic complex of the
present invention.
[0147] In the light-emitting element like this, holes injected from
the first electrode 101 and electrons injected from the second
electrode 102 are recombined in the light-emitting layer 113 to
bring the fluorescent compound to be in an excited state. The
fluorescent compound in an excited state emits light while
returning to the ground state. In this case, the organometallic
complex of the present invention acts as a sensitizer for the
fluorescent compound to make more molecules of the fluorescent
compound be in the singlet excited state. As noted above, a
light-emitting element with good light emission efficiency can be
obtained by using the organometallic complex according to the
present invention as a sensitizer. It is to be noted that the first
electrode 101 functions as an anode and the second electrode 102
functions as a cathode in the light-emitting element in Embodiment
Mode 5. Here, the light-emitting layer 113 includes an
organometallic complex of the present invention, and a fluorescent
compound which can emit light with a longer wavelength than the
organometallic complex of the present invention. The light-emitting
layer 113 may preferably have a structure in which a substance that
has a larger singlet excitation energy than the fluorescent
compound and has a larger triplet excitation energy than the
organometallic complex of the present invention is used as a host,
and the organometallic complex of the present invention and the
fluorescent compound are dispersedly contained as a guest.
[0148] There is no particular limitation on a substance (i.e.,
host) used for dispersing the organometallic complex of the present
invention and the fluorescent compound, and a substance which is
used as a host in Embodiment Mode 2, or the like can be used.
[0149] In addition, there is also no particular limitation on the
fluorescent complex; however, a compound which can exhibit emission
of red light to infrared light is preferable, for example,
4-dicyanomethylene-2-isopropyl-6-[2-(1,1,7,7-tetramethyljulolidin-9-yl)et-
henyl]-4H-pyran (abbreviation: DCJTI), magnesium phthalocyanine,
magnesium porphyrin, phthalocyanine and the like are
preferable.
[0150] Note that the first electrode 101 and the second electrode
102 may both have the same structure as the first electrode and the
second electrode in Embodiment Mode 2, respectively.
[0151] In Embodiment Mode 5, as shown in FIG. 1, the hole-injecting
layer 111, the hole-transporting layer 112, the
electron-transporting layer 114, and the electron-injecting layer
115 are provided; also to these layers, the structures of the
respective layers described in Embodiment Mode 2 may be applied.
However, these layers are not necessarily provided and may be
provided according to element characteristics.
[0152] The foregoing light-emitting element can emit light highly
efficiently by using the organometallic complex of the present
invention as a sensitizer.
Embodiment Mode 6
[0153] In Embodiment Mode 6, modes of light-emitting devices
including the light-emitting element of the present invention are
explained with reference to FIGS. 4A to 4C. FIGS. 4A to 4C show
cross-sectional views of the light-emitting devices. In FIGS. 4A to
4C, a portion surrounded by dotted lines of a rectangular shape is
a transistor 11 which is provided to drive a light-emitting element
12 of the present invention. The light-emitting element 12 is a
light-emitting element of the present invention in which a layer 15
including a light-emitting layer is formed between a first
electrode 13 and a second electrode 14, and the light-emitting
layer includes an organometallic complex of the present invention.
Specifically, the light-emitting element 12 has the structure as
shown in Embodiment Mode 2. A drain region of the transistor 11 and
the first electrode 13 are electrically connected to each other by
a wiring 17 that runs through a first interlayer insulating film 16
(16a, 16b, and 16c). The light-emitting element 12 is isolated from
other light-emitting elements provided adjacent to the
light-emitting element 12 by a partition layer 18. The
light-emitting device having such a structure of the present
invention is provided over a substrate 10 in Embodiment Mode 6.
[0154] Note that each of the transistors 11 shown in FIGS. 4A to 4C
is a top gate type in which a gate electrode is provided on a side
opposite to a substrate, regarding the semiconductor layer as a
center. However, a structure of the transistor 11 is not
particularly limited, and a bottom gate type may also be employed,
for example. Further, in the case of a bottom-gate structure, a TFT
in which a protective film is formed over the channel-forming
semiconductor layer (a channel protection type TFT) can be used, or
a TFT in which a part of the channel-forming semiconductor layer is
concave (a channel etch type TFT) can also be used.
[0155] The semiconductor layer included in the transistor 11 may be
either of a crystalline semiconductor or an amorphous
semiconductor. Further, it may be semi-amorphous or the like.
[0156] Note that the semiamorphous semiconductor is as follows. A
semi-amorphous semiconductor is a semiconductor having an
intermediate state between an amorphous structure and a crystalline
structure (including single crystal and polycrystal) and a third
state which is stable in free energy. It further includes a
crystalline region having a short range order and lattice
distortion. A Raman spectrum derived from L-O phonon is shifted to
a lower wavenumber side than 520 cm.sup.-1. In X-ray diffraction,
diffraction peaks of (111) and (220) due to a Si crystal lattice
are observed. Hydrogen or halogen of at least 1 atomic % is
contained to terminate a dangling bond. It is also referred to as a
microcrystalline semiconductor. The semiamorphous semiconductor is
as follows. A semi-amorphous semiconductor is a semiconductor
having an intermediate state between an amorphous structure and a
crystalline structure (i is formed by decomposing a gas including
silicon with glow discharge decomposition (plasma CVD). SiH.sub.4
is a typical gas containing silicon, and additionally,
Si.sub.2H.sub.6, SiH.sub.2Cl.sub.2, SiHCl.sub.3, SiCl.sub.4,
SiF.sub.4, or the like can be used. The gas containing silicon may
be diluted with H.sub.2 or H.sub.2 or and one or more kinds of rare
gas elements selected from He, Ar, Kr, and Ne. The dilution ratio
is 1:2 to 1:1000, the pressure is approximately 0.1 to 133 Pa, and
the power source frequency is 1 to 120 MHz, and preferably 13 to 60
MHz. A substrate heating temperature may be less than or equal to
300.degree. C., preferably, 100 to 250.degree. C. A concentration
of an atmospheric constituent impurity such as oxygen, nitrogen, or
carbon, as an impurity element in the film, is preferably
1.times.10.sup.20 atoms/cm.sup.3 or less; in particular, a
concentration of oxygen is 5.times.10.sup.19 atoms/cm.sup.3 or
less, preferably 1.times.10.sup.19 atoms/cm.sup.3 or less. Note
that the mobility of a TFT (thin film transistor) using the
semiamorphous semiconductor is approximately 1 cm.sup.2/Vsec to 10
cm.sup.2/Vsec.
[0157] As a specific example of a crystalline semiconductor layer,
ones made with single crystalline silicon, polycrystalline silicon,
silicon germanium, or the like can be cited. They can be formed by
laser crystallization, or crystallization by a solid phase epitaxy
method using nickel or the like, for example. Single crystal
silicon can be used as the semiconductor layer of the transistor
11, by a SmartCut method (registered trademark), for example.
[0158] In a case where a semiconductor layer is formed using an
amorphous substance, e.g., amorphous silicon, it is preferable that
a light-emitting device have circuits including only n-channel
transistors as the transistor 11 and the other transistors
(transistors included in a circuit for driving a light-emitting
element). In the other cases, a light-emitting device may have a
circuit including either an n-channel transistor or a p-channel
transistor, or may have a circuit including both an n-channel
transistor and a p-channel transistor.
[0159] Further, the first interlayer insulating films 16a to 16c
may be a multilayer as shown in FIGS. 4A, 4C, or a single layer
Note that the first interlayer insulating film 16a is formed using
an inorganic material such as silicon oxide or silicon nitride; and
the first interlayer insulating film 16b is formed using a
self-planarizing substance such as acrylic, siloxane (an organic
group in which a skeleton structure is formed of a bond of silicon
(Si) and oxygen (O) and at least hydrogen is contained as a
substituent), or silicon oxide which can be formed by an
application method. In addition, the first interlayer insulating
film 16c is formed using a silicon nitride film containing argon
(Ar). The substances constituting each of the layers are not
particularly limited; therefore, substances other than the
substances mentioned here may also be used. Alternatively, a layer
made with a substance other than those may be used in combination.
As described above, the first interlayer insulating films 16a to
16c may be formed with either an inorganic material or an organic
material, or both of them.
[0160] The partition layer 18 preferably has a shape in which a
curvature radius changes continuously in an edge portion. In
addition, the partition layer 18 is formed with acrylic, siloxane,
resist, silicon oxide, or the like. Note that the partition layer
18 may be formed with either a film of an inorganic material or a
film of an organic material, or both of them.
[0161] In FIGS. 4A and 4C, only the first interlayer insulating
films 16a to 16c are provided between the transistor 11 and the
light-emitting element 12. However, as shown in FIG. 4B, a second
interlayer insulating film 19 (19a and 19b) may also be provided in
addition to the first interlayer insulating film 16 (16a and 16b).
In the light-emitting device shown in FIG. 4B, the first electrode
13 penetrates the second interlayer insulating film 19 and connects
to the wiring 17.
[0162] The second interlayer insulating film 19 may have a
multilayer structure or a single-layer structure like the first
interlayer insulating film 16. The second interlayer insulating
film 19a is made from acrylic, siloxane (an organic group including
a skeleton of a silicon-oxygen bond (Si--O bond) and including at
least hydrogen as a substituent), or a self-planarizing substance
which can be formed as a film by an application method, such as
silicon oxide. The second interlayer insulating film 19b is formed
from a silicon nitride film containing argon (Ar). Note that there
are no particular limitations on substances forming each layer, and
a substance other than the foregoing substances can also be used. A
layer made from a substance other than the foregoing materials may
be further combined. As described above, the second interlayer
insulating film 19 may be formed with either a film of an inorganic
material or a film of an organic material, or both of them.
[0163] When both the first electrode 13 and the second electrode 14
are formed from light-transmitting substances in the light-emitting
element 12, light emission can be extracted through both the first
electrode 13 and the second electrode 14 as indicated by the
outlined arrows in FIG. 4A. When only the second electrode 14 is
formed from a light-transmitting material, light emission can be
extracted through only the second electrode 14 as indicated by the
outlined arrow in FIG. 4B. In this case, it is preferable to form
the first electrode 13 from a highly reflective material or provide
a film formed from a highly reflective material (reflective film)
below the first electrode 13. When only the first electrode 13 is
formed from a light-transmitting material, light emission can be
extracted through only the first electrode 13 as indicated by the
outlined arrow in FIG. 4C. In this case, it is preferable to form
the second electrode 14 from a highly reflective material or
provide a reflective film above the second electrode 14.
[0164] In the light-emitting element 12, the layer 15 may be
stacked so as to operate the light-emitting element 12 when a
voltage is applied so that a potential of the second electrode 14
becomes higher than that of the first electrode 13, or the layer 15
may be stacked so as to operate the light-emitting element 12 when
a voltage is applied so that a potential of the second electrode 14
becomes lower than that of the first electrode 13. In the former
case, the transistor 11 is an n-channel transistor, and in the
latter case, the transistor 11 is a p-channel transistor.
[0165] As described above, an active matrix light-emitting device
in which drive of the light-emitting element is controlled by
transistors is explained in Embodiment Mode 6. However, a passive
matrix light-emitting device, in which the light-emitting element
is driven without providing a particular drive element such as a
transistor over the same substrate as the light-emitting element,
may also be employed.
[0166] The light-emitting device shown in Embodiment Mode 6 has a
feature of realizing emission color with high color purity emission
colors, since the light-emitting device uses a light-emitting
element of the present invention. Further, the light-emitting
device also has a feature of various emission colors. Furthermore,
the light-emitting device also has a feature of high emission
efficiency and low power consumption.
Embodiment Mode 7
[0167] Because a light-emitting device in which the light-emitting
element of the present invention having a sharp emission spectrum
is used has excellent color purity and can display images of high
quality, by application of the light-emitting device of the present
invention to a display portion of an electronic device, an
electronic device that displays images of superior quality can be
obtained. In addition, the light-emitting device including the
light-emitting element of the present invention can be driven with
low power consumption because it has excellent emission efficiency.
Therefore, electronic devices with low power consumption can be
obtained by applying the light-emitting device of the present
invention to the display portions of the electronic devices, and
for example, a telephone or the like that has long battery standing
time, and the like can be obtained. Hereinafter, some examples of
electronic devices incorporating a light-emitting device to which a
light-emitting element of the present invention is applied are
shown.
[0168] FIG. 5A is a computer manufactured by applying the present
invention, which includes a main body 511, a casing 512, a display
portion 513, a keyboard 514, and the like. The computer can be
completed by incorporating the light-emitting device including the
light-emitting element of the present invention thereinto as a
display portion.
[0169] FIG. 5B is a telephone manufactured by applying the present
invention, in which a main body 522 includes a display portion 521,
an audio output portion 524, an audio input portion 525, operation
switches 526 and 527, an antenna 523, and the like. The telephone
can be completed by incorporating the light-emitting device
including the light-emitting element of the present invention in
the display portion.
[0170] FIG. 5C is a television set manufactured by applying the
present invention, which includes a display portion 531, a casing
532, a speaker 533, and the like. The television receiver can be
completed by incorporating a light-emitting device having a
light-emitting element according to the present invention therein
as the display portion.
[0171] As the above, the light-emitting device of the present
invention is very suitable for a display portion of each of
electronic devices.
[0172] Although the computer and the like are described in
Embodiment Mode 7, besides, the light-emitting device including the
light-emitting element of the present invention may also be
incorporated in a navigation system, an illumination apparatus, or
the like.
[0173] In addition, the light-emitting device of the present
invention can also be used as an illumination apparatus. One mode
using the light-emitting element of the present invention for a
lighting device will be described with reference to FIG. 18 to FIG.
20.
[0174] FIG. 18 illustrates an example of a liquid crystal display
device in which a light-emitting element including the
organometallic complex described in Embodiment Mode 1, i.e., the
light-emitting element described in Embodiment Mode 2, is used as a
backlight. The liquid crystal display device shown in FIG. 18
includes a chassis 901, a liquid crystal layer 902, a backlight
903, and a chassis 904. The liquid crystal layer 902 is connected
to a driver IC 905. The light-emitting element of the present
invention is used as the backlight 903, to which current is
supplied through a terminal 906.
[0175] The backlight 903 for the liquid crystal display device
should emit white light or three colors emission of red, green and
blue. In the light-emitting element of the present invention, as a
method for emitting white light, a plurality of light-emitting
layers may be provided as described in Embodiment Mode 3 or
Embodiment Mode 4.
[0176] In addition, light-emitting elements for red, green and blue
are arranged in matrix, and the light-emitting elements are made to
emit light at the same time, so that white emission color can be
obtained by the whole backlight 903. In this case, the
light-emitting element for each color of red, green and blue may be
provided to correspond to each pixel for red, green or blue.
[0177] Note that the backlight 903 may be formed from one
light-emitting element or a plurality of light-emitting elements of
the present invention. Alternatively, the backlight 903 may be
formed from plural types of light-emitting elements, which emit
different colors from the light-emitting element of the present
invention.
[0178] As described above, a light-emitting element of the present
invention can be applied to a backlight of a liquid crystal display
device. The area of the backlight can be enlarged, and thus the
liquid crystal display device also can be enlarged. Further, a
high-quality image can be provided by using a light-emitting
element of the present invention with high color purity. Moreover,
a backlight with high emission efficiency and reduced power
consumption can be provided by using the light-emitting element
having high emission efficiency. Moreover, since the backlight
using the light-emitting element of the present invention is thin
and consumes less electric power, reduction in thickness and power
consumption of the liquid crystal display device is possible.
[0179] FIG. 19 illustrates an example in which a light-emitting
element of the present invention is used for a desk lamp which is
an example of illumination apparatuses. The desk lamp shown in FIG.
19 includes a chassis 2001 and a light source 2002, and the
light-emitting element of the present invention is used for the
light source 2002. The light source 2002 may be formed from one
light-emitting element or a plurality of light-emitting elements of
the present invention. Alternatively, the light source 2002 may be
formed from plural types of light-emitting elements, which emit
different colors from the light-emitting element of the present
invention. As described above, the light source 2002 can be
manufactured by using a light-emitting element of the present
invention. In addition, the light source 2002 formed using the
light-emitting element having high emission efficiency have high
emission efficiency and low power consumption, and thus the desk
lamp using the light source also has high emission efficiency and
low power consumption.
[0180] FIG. 20 illustrates an example in which a light-emitting
element of the present invention is used for an indoor illumination
apparatus 3001. The illumination apparatus 3001 may be formed from
one light-emitting element or a plurality of light-emitting
elements of the present invention. Alternatively, the illumination
apparatus 3001 may be formed from plural types of light-emitting
elements, which emit different colors from the light-emitting
element of the present invention. As described above, the
illumination apparatus 3001 can be manufactured by using a
light-emitting element of the present invention. The area of the
illumination apparatus 3001 formed using the light-emitting element
can be enlarged, and thus it can be used as a large area
illumination apparatus. The illumination apparatus 3001 formed
using the light-emitting element having high emission efficiency
can be an illumination apparatus which is thin and consumes less
power.
Example 1
Synthesis Example 1
[0181] Synthesis Example 1 will specifically describe a synthesis
example of an organometallic complex of the present invention
represented by the structural formula (1) of Embodiment Mode 1,
(acetylacetonato)bis[2-(4-fluorophenyl)-3-methoxy-5-methylpyrazinato]irid-
ium(III) (abbreviation: [Ir(MOFppr-Me).sub.2(acac)]).
##STR00038##
<Step 1: Synthesis of
2-chloro-3-(4-fluorophenyl)pyrazine>
[0182] First, 5.06 g of 2,3-dichloropyrazine, 5.23 g of
4-fluorophenyl boronic acid, 22.16 g of cesium carbonate, and 200
mL of dioxane were put in a three-neck flask equipped with a reflux
pipe, and 0.467 g of tris(dibenzylideneacetone)dipalladium(0)
(abbreviation: Pd.sub.2(dba).sub.3) and 2.5 mL of
tricyclohexylphosphine (abbreviation: Cy.sub.3P) were added thereto
while the mixture was stirred under a nitrogen atmosphere, and they
were reacted at 85.degree. C. for 11 hours. After the reaction, the
reaction solution was cooled down to room temperature and
filtrated. A solvent of the obtained filtrate was distilled off,
and the obtained residue was refined with a column chromatography
using dichloromethane as a development solvent, so that
2-chloro-3-(4-fluorophenyl)pyrazine was obtained (light yellow
powder, yield: 55%). A synthesis scheme of Step 1 is shown by the
following (a1-1).
##STR00039##
<Step: 2 Synthesis of
2-(4-fluorophenyl)-3-methoxypyrazine>
[0183] Next, 3.87 g of 2-chloro-3-(4-fluorophenyl)pyrazine, 2.01 g
of sodium methoxide, and 30 mL of methanol were put in a three-neck
flask equipped with a reflux pipe, and reacted by being heated and
refluxed under a nitrogen atmosphere for three hours. After the
reaction, the reaction solution was cooled down to room
temperature, water was added thereto, and an organic layer was
extracted with dichloromethane. The obtained organic layer was
washed with a saturated saline and water, and dried with magnesium
sulfate. Then, magnesium sulfate was removed by filtration and the
solvent was distilled off, so that
2-(4-fluorophenyl)-3-methoxypyrazine was obtained (milky white
powder, yield: 96%). A synthetic scheme of Step 2 is shown in the
following (a1-2).
##STR00040##
<Step 3: 2-(4-fluorophenyl)-3-methoxy-5-methylpyrazine
(Abbreviation: HMOFppr-Me)>
[0184] Further, 3.24 g of 2-(4-fluorophenyl)-3-methoxypyrazine and
80 mL of diethyleter were put in a three-neck flask, and 20 mL of a
diethylether solution of methyllithium (1.20 mol/L) was dropped
while the mixture was stirred under a nitrogen atmosphere, and
stirred to be reacted for one week. After the reaction, water was
added to the reaction solution, and an organic layer was extracted
with dichloromethane. The obtained organic layer was washed with
water, and dried with magnesium sulfate. Magnesium sulfate was
removed by filtration and the solvent was distilled off. The
obtained residue was refined with a column chromatography using
dichloromethane as a development solvent, so that an objective
pyrazine derivative, HMOFppy-Me (milky white powder, yield: 15%). A
synthesis scheme of Step 3 is shown by the following (a1-3).
##STR00041##
<Step 4: Synthesis of
di-.mu.-chloro-bis{bis[2-(4-fluorophenyl)-3-methoxy-5-methylpyrazinato]ir-
idium(III)} (Abbreviation: [Ir(MOFppr-Me).sub.2Cl].sub.2)>
[0185] Next, 24 mL of 2-ethoxyethanol, 8 mL of water, 0.52 g of the
pyrazine derivative HMOFppy-Me obtained in Step 3, and 0.36 g of
iridium chloride hydrate (IrCl.sub.3.H.sub.2O) (manufactured by
Sigma-Aldrich Corp.) were put in an egg plant flask equipped with a
reflux pipe, and the inside thereof was substituted by argon. Then,
the reaction container was subjected to irradiation of a microwave
(2.45 GHz, 150 W) for one hour to be heated and reacted. Orange
powder precipitated from the reaction solution was filtrated and
washed with ethanol, so that a binuclear complex,
[Ir(MOFppr-Me).sub.2Cl].sub.2 was obtained (yield: 45%). A
synthesis scheme of Step 4 is shown by the following (b1).
##STR00042##
<Step 5: Synthesis of
(acetylacetonato)bis[2-(4-fluorophenyl)-3-methoxy-5-methylpyradinatoiridi-
um(III) (Abbreviation: [Ir(MOFppr-Me).sub.2(acac)]>
[0186] Further, 30 mL of 2-ethoxyethanol, 0.36 g of the binuclear
complex [Ir(MOFppr-Me).sub.2Cl].sub.2 obtained in Step 4, 0.083 mL
of acetylacetone, 0.29 g of sodium carbonate were put in an egg
plant flask equipped with a reflux pipe, and the inside thereof was
substituted by argon. Then, this reaction container was subjected
to irradiation of a microwave (2.45 GHz, 150 W) for 30 minutes to
be heated and reacted. The reaction solution was cooled down to
room temperature, filtrated, and the solvent wad distilled off. The
obtained residue was recrystallized with dichloromethane-methanol,
so that an organometallic complex of the present invention,
[Ir(MOFppr-Me).sub.2(acac)] was obtained (orange micro crystal,
yield: 33%). A synthesis scheme of Step 5 is shown by the following
(c1).
##STR00043##
[0187] An analysis result by nuclear magnetic resonance
spectrometry (.sup.1H-NMR) of the orange micro crystal obtained in
Step 5 is shown below. FIG. 6 is a .sup.1H-NMR chart thereof.
According to FIG. 6, it is found that the organometallic complex of
the present invention [Ir(MOFppr-Me).sub.2(acac)] represented by
the above structural formula (1) was obtained in Synthesis Example
1.
[0188] .sup.1H-NMR. .delta. (CDCl.sub.3): 1.82 (s, 6H), 2.56 (s,
6H), 4.21 (s, 6H), 5.24 (s, 1H), 5.82 (d, 2H), 6.56 (t, 2H), 7.89
(s, 2H), 8.30 (m, 2H).
[0189] An absorption spectrum and an emission spectrum (excitation
wavelength .about.468 nm) of [Ir(MOFppr-Me).sub.2(acac)] were
measured. The absorption spectrum was measured by using a degassed
dichloromethane solution (0.14 mmol/L) at room temperature by using
an ultraviolet-visible spectrophotometer (V-550, by JASCO
Corporation). The emission spectrum was measured by using a
degassed dichloromethane solution (0.48 mmol/L) at room temperature
by using a spectrofluorometer (FS920, by Hamamatsu Photonics K. K.)
The measurement results are shown in FIG. 7. The horizontal axis
indicates a wavelength and the vertical axis indicates a molar
absorption coefficient and an emission intensity.
[0190] The peak of the emission spectrum lies at 570 nm, and orange
emission was observed.
[0191] It is observed that the organometallic complex
[Ir(MOFppr-Me).sub.2(acac)] of the present invention has several
absorption peaks in the visible light region. This absorption is
unique to some organometallic complexes such as an ortho-metallated
complex, and is considered to correspond to singlet MLCT
transition, triplet .pi.-.pi.* transition, triplet MLCT transition,
or the like. In particular, the longest wavelength absorption peak
extends over a broad range in the visible light region. Thus, this
absorption peak is considered to correspond to the triplet MLCT
transition. In other words, it is considered that the
organometallic complex [Ir(MOFppr-Me).sub.2(acac)] of the present
invention is a compound capable of direct photo-excitation or
intersystem crossing to a triplet excited state. Therefore, it can
be considered that obtained emission is light emission from the
triplet excited state, that is, phosphorescence.
Example 2
[0192] Example 2 will specifically describe a light-emitting
element using the organometallic complex of the present invention,
[Ir(MOFppr-Me).sub.2(acac)] synthesized in Synthesis Example 1 of
Example 1, as a light-emitting substance. FIG. 1 illustrates a
structure of the light-emitting element.
[0193] First, a glass substrate, over which indium tin oxide
containing silicon oxide (ITSO) was formed with a thickness of 110
nm, was prepared. The periphery of the ITSO surface was covered
with an insulating film so that a surface of ITSO of 2 mm.times.2
mm was exposed. ITSO was formed as a first electrode 101 serving as
an anode of the light-emitting element. As a pretreatment for
forming the light-emitting element over the substrate, the surface
of the substrate was washed with a porous resin brush, and baked at
200.degree. C. for one hour, then, a UV ozone treatment was
conducted for 370 seconds.
[0194] Subsequently, the substrate was fixed to a holder provided
in a vacuum evaporation apparatus so that the surface provided with
ITSO faced downward.
[0195] After pressure in the vacuum evaporation apparatus was
reduced to 10.sup.-4 Pa, NPB represented by the following
structural formula (i) and molybdenum(VI) oxide were co-deposited
so as to meet NPB: molybdenum(VI) oxide=4:1 (mass ratio), whereby a
hole-injecting layer 111 was formed. The hole-injecting layer 111
was 50 nm thick. Note that a co-evaporation method is an
evaporation method in which a plurality of different substances is
concurrently vaporized from respective different evaporation
sources. Next, NPB was deposited to be 10 nm thick, whereby a
hole-transporting layer 112 was formed. Further, over the
hole-transporting layer 112,
4-(9H-carbazol-9-yl)-4'-(5-phenyl-1,3,4-oxadiazol-2-yl)triphenylamine
(abbreviation: YGAO11) and [Ir(MOFppr-Me).sub.2(acac)] synthesized
in Synthesis Example 1 were co-evaporated such that the mass ratio
of YGAO11 to [Ir(MOFppr-Me).sub.2(acac)] was 1:0.05 (YGAO11:
[Ir(MOFppr-Me).sub.2(acac)]=1:0.05), and thereby a light-emitting
layer 113 was formed. The film thickness was 30 nm. Then, BAlq
represented by the following structural formula (iii) was deposited
to be 10 nm thick, whereby an electron-transporting layer 114 was
formed. Further, over the electron-transporting layer 114,
Alq.sub.3 represented by the following structural formula (Iv) and
lithium (Li) were co-deposited so as to meet Alq.sub.3:Li=1:0.01
(mass ratio), whereby an electron-injecting layer 115 was formed.
The film thickness was 40 nm. Finally, aluminum was formed to be
200 nm thick as a second electrode 102 which functions as a
cathode, whereby a light-emitting element of the present invention
was obtained. It is to be noted that, in all of the above
evaporation processes, evaporation was performed by a resistance
heating method.
##STR00044##
[0196] After sealing this light-emitting element in a glove box
with a nitrogen atmosphere so as not to expose the light-emitting
element to air, operation characteristics of the light-emitting
element were measured. Note that the measurements were performed at
room temperature (an atmosphere kept at 25.degree. C.).
[0197] FIG. 8 shows luminance-current efficiency characteristics of
the light-emitting element. This light-emitting element emits light
at a luminance of 1170 cd/m.sup.2 by allowing current flow with a
current density of 5.46 mA/cm.sup.2. At this time, the current
efficiency was 21.4 cd/A and thus the light-emitting element
exhibited a high emission efficiency. When the current efficiency
was converted to an external quantum efficiency, the external
quantum efficiency was 6.31%. In addition, FIG. 9 shows CIE
chromaticity coordinates at this time and the CIE chromaticity
coordinates were (x, y)=(0.47, 0.52). Thus, yellow orange light
emission was obtained. As shown in FIG. 9, the CIE chromaticity
coordinates of the light-emitting element of this example exist
outside the color reproduction region of NTSC standard (which is
the inside of the triangle in FIG. 10), and thus it is known that
the light-emitting element exhibits high color purity.
[0198] FIG. 10 shows an emission spectrum when a current at a
current density of 0.5 mA/cm.sup.2 was supplied to this
light-emitting element. As shown in FIG. 10, the emission spectrum
has a peak at 558 nm, and it indicates that the peak results from
light emission of [Ir(MOFppr-Me).sub.2(acac)] which is an
organometallic complex of the present invention. Full width at
half-maximum of the emission spectrum was 58 nm and the spectrum
was sharp.
[0199] FIG. 11, FIG. 12, FIG. 13, FIG. 14 and FIG. 15 show current
density-luminance characteristics, voltage-luminance
characteristics, voltage-current characteristics, luminance-power
efficiency characteristics, and luminance-external quantum
efficiency characteristics of the fabricated light-emitting
element, respectively.
Example 3
Synthesis Example 2
[0200] Synthesis example 2 will specifically describe a synthesis
example of an organometallic complex of the present invention
represented by the structural formula (12) of Embodiment Mode 1,
(acetylacetonato)bis(2-phenyl-3-methoxy-5-methylpyrazinato)iridium(III)
(abbreviation: [Ir(MOppr-Me).sub.2(acac)]).
##STR00045##
<Step 1: Synthesis of 2-phenyl-3-methoxypyrazine>
[0201] First, in a three-neck flask, 11.30 g of 2-methoxypyrazine
and 200 mL of diethylether were put, and a dibutyl ether solution
(2.1 mol/L) of phenyl lithium was dropped thereto while the mixture
was cooled down with ices and stirred under a nitrogen atmosphere,
and stirred to be reacted for 20 hours. After the reaction, water
was added to the reaction solution, and an organic layer was
extracted with ethyl acetate. The obtained organic layer was washed
with water, and dried with magnesium sulfate. Magnesium sulfate was
removed by filtration and the solvent was distilled off. The
obtained residue was refined with a column chromatography using
dichloromethane as a development solvent, so that
2-phenyl-3-methoxypyrazine was obtained (light yellow powder,
yield: 12%). A synthesis scheme of Step 1 is shown by the following
(a2-1).
##STR00046##
<Step 2: Synthesis of 2-phenyl-3-methoxy-5-methylpyrazine
(Abbreviation: HMOppr-Me)>
[0202] First, 2.16 g of 2-phenyl-3-methoxypyrazine obtained in the
above Step 1 and 30 mL of diethylether were put in a three-neck
flask, and 14.5 mL of a diethylether solution (1.20 mol/L) of
methyllithium was dropped thereto while the mixture was stirred
under a nitrogen atmosphere, and then stirred to be reacted for 20
hours. After the reaction, water was added to the reaction
solution, and an organic layer was extracted with dichloromethane.
The obtained organic layer was washed with water, and dried with
magnesium sulfate. Magnesium sulfate was removed by filtration and
the solvent was distilled off. The obtained residue was refined
with a column chromatography using dichloromethane as a development
solvent, so that an objective alkoxypyrazine derivative, HMOppe-Me,
was obtained (milky white powder, yield 20%). A synthesis scheme of
Step 2 is shown by the following (a2-2).
##STR00047##
<Step 3: Synthesis of
di-.mu.-chloro-bis[bis(2-phenyl-3-methoxy-5-methylpyrazinato]iridium(III)-
} (Abbreviation: [Ir(MOppr-ME).sub.2Cl].sub.2)>
[0203] Next, 15 mL of 2-ethoxyethanol, 5 mL of water, 0.47 g of the
pyrazine derivative HMOppr-Me obtained in Step 2 described above,
and 0.35 g of iridium chloride hydrate (IrCl.sub.3.H.sub.2O)
(manufactured by Sigma-Aldrich Corp.) were put in an egg plant
flask with a reflux pipe attached, and the inside thereof was
substituted by argon. Then, the reaction container was subjected to
irradiation of a microwave (2.45 GHz, 120 W) for 30 minutes to be
heated and reacted. Red powder precipitated from the reaction
solution was filtrated and washed with ethanol, so that a binuclear
complex, [Ir(MOppr-Me).sub.2Cl].sub.2 was obtained (yield: 33%). A
synthesis scheme of Step 3 is shown by the following (c2).
##STR00048##
<Step 4: Synthesis of
(acethylacetonato)bis(2-phenyl-3-methoxy-5-methylpyrazinato)iridium(III)]
(Abbreviation: [Ir(MOppr-Me).sub.2(acac)])>
[0204] Further, 10 mL of 2-ethoxyethanol, 0.25 g of the binuclear
complex [Ir(MOppr-Me).sub.2Cl].sub.2 obtained in Step 3 described
above, 0.06 mL of acethylacetone, and 0.21 g of sodium carbonate
were put in an egg plant flask with a reflux pipe attached, and the
inside thereof was substituted by argon. Then, the reaction
container was subjected to irradiation of a microwave (2.45 GHz,
100 W) for 30 minutes to be heated and reacted. The reaction
solution was cooled down to room temperature, filtrated, and the
solvent was distilled off. The obtained residue was refined with a
column chromatography using dichloromethane as a development
solvent, so that an organometallic complex of the present
invention, [Ir(MOppr-Me).sub.2(acac)] was obtained (orange powder,
yield: 10%). A synthesis scheme of Step 4 is shown by the following
(d2).
##STR00049##
[0205] An analysis result by nuclear magnetic resonance
spectrometry (.sup.1H-NMR) of the orange powder obtained in Step 4
is described below. FIG. 16 is a .sup.1H-NMR chart thereof. Thus,
it is found from FIG. 16 that the organometallic complex of the
present invention [Ir(MOppr-Me).sub.2(acac)] represented by the
above structural formula (12) was obtained in Synthetic Example
1.
[0206] .sup.1H-NMR. .delta. (CDCl.sub.3): 1.80 (s, 6H), 2.56 (s,
6H), 4.20 (s, 6H), 5.21 (s, 1H), 6.22 (dd, 2H), 6.68 (dt, 2H), 6.82
(dt, 2H), 7.98 (s, 2H), 8.29 (dd, 2H).
[0207] An absorption spectrum and an emission spectrum (excitation
wavelength: 468 nm) of [Ir(Moppr-Me).sub.2(acac)] were measured.
The absorption spectrum was measured by using a degassed
dichloromethane solution (0.12 mmol/L) at room temperature by using
an ultraviolet-visible spectrophotometer (V-550, by JASCO
Corporation). The emission spectrum was measured by using a
degassed dichloromethane solution (0.42 mmol/L) at room temperature
by using a spectrofluorometer (FS920, by Mamamatsu Photonics K. K.)
The measurement results are shown in FIG. 17. The horizontal axis
indicates a wavelength and the vertical axis indicates a molar
absorption coefficient and an emission intensity.
[0208] The peak of the emission spectrum lies at 592 nm, and orange
emission was observed.
[0209] It is observed that the organometallic complex
[Ir(MOppr-Me).sub.2(acac)] has several absorption peaks in the
visible light region. This absorption is unique to some
organometallic complexes such as an ortho-metallated complex, and
is considered to correspond to singlet MLCT transition, triplet
.pi.-.pi.* transition, triplet MLCT transition, or the like. In
particular, the longest wavelength absorption peak extends over a
broad range in the visible light region. Thus, this absorption is
considered to correspond to the triplet MLCT transition. In other
words, it is considered that the organometallic complex
[Ir(MOppr-Me).sub.2(acac)] is a compound capable of direct
photo-excitation or intersystem crossing to a triplet excited
state. Therefore, it can be considered that obtained emission is
light emission from the triplet excited state, that is,
phosphorescence.
[0210] This application is based on Japanese Patent Application
Serial No. 2007-148458 filed with Japan Patent Office on Jun. 4,
2007, the entire contents of which are hereby incorporated by
reference.
* * * * *