U.S. patent application number 15/227441 was filed with the patent office on 2016-11-24 for organometallic iridium complex, light-emitting element, light-emitting device, electronic device, and lighting device.
This patent application is currently assigned to Semiconductor Energy Laboratory Co., Ltd.. The applicant listed for this patent is Semiconductor Energy Laboratory Co., Ltd.. Invention is credited to Hideko INOUE, Miki KANAMOTO, Nobuharu OHSAWA, Satoshi SEO.
Application Number | 20160343959 15/227441 |
Document ID | / |
Family ID | 52626193 |
Filed Date | 2016-11-24 |
United States Patent
Application |
20160343959 |
Kind Code |
A1 |
OHSAWA; Nobuharu ; et
al. |
November 24, 2016 |
Organometallic Iridium Complex, Light-Emitting Element,
Light-Emitting Device, Electronic Device, and Lighting Device
Abstract
An organometallic iridium complex has high emission efficiency
and a long lifetime. The iridium complex includes the structure
represented by Formula (G1). In the formula, Ar represents a
substituted or unsubstituted arylene group having 6 to 13 carbon
atoms. R.sup.1 to R.sup.6 independently represent any one of
hydrogen and a substituted or unsubstituted alkyl group having 1 to
6 carbon atoms, and one of R.sup.2 and R.sup.6 represents the alkyl
group. X represents a carbon atom or a nitrogen atom, and when X
represents a carbon atom, hydrogen or an alkyl group having 1 to 6
carbon atoms is bonded to the carbon atom. A dihedral angle between
a ring bonded to R.sup.1 and a phenyl group bonded to R.sup.2 to
R.sup.6 is 30.degree. or more and 90.degree. or less. An interior
angle of the pyridine/pyrimidine ring facing R.sup.1 is within a
range of 118.degree. to 122.degree.. ##STR00001##
Inventors: |
OHSAWA; Nobuharu; (Zama,
JP) ; INOUE; Hideko; (Atsugi, JP) ; SEO;
Satoshi; (Sagamihara, JP) ; KANAMOTO; Miki;
(Atsugi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Semiconductor Energy Laboratory Co., Ltd. |
Kanagawa-ken |
|
JP |
|
|
Assignee: |
Semiconductor Energy Laboratory
Co., Ltd.
Kanagawa-ken
JP
|
Family ID: |
52626193 |
Appl. No.: |
15/227441 |
Filed: |
August 3, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
14482536 |
Sep 10, 2014 |
9412956 |
|
|
15227441 |
|
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01L 51/0074 20130101;
C07F 15/0033 20130101; H01L 51/5016 20130101; H01L 51/5056
20130101; H05B 33/14 20130101; H01L 51/5234 20130101; H01L 51/5092
20130101; H01L 51/5088 20130101; C09K 11/06 20130101; H01L 51/0059
20130101; H01L 51/5072 20130101; H01L 51/0072 20130101; C09K
2211/185 20130101; C09K 2211/1029 20130101; C09K 2211/1007
20130101; H01L 2251/5384 20130101; H01L 51/56 20130101; H01L
51/0085 20130101; C09K 2211/1044 20130101 |
International
Class: |
H01L 51/00 20060101
H01L051/00; C09K 11/06 20060101 C09K011/06; C07F 15/00 20060101
C07F015/00 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 12, 2013 |
JP |
2013-189385 |
Claims
1. A compound comprising a structure represented by Formula (G1):
##STR00050## wherein: Ar represents an unsubstituted arylene group
having 6 to 13 carbon atoms; R.sup.1 to R.sup.6 independently
represent any one of hydrogen and a substituted or unsubstituted
alkyl group having 1 to 6 carbon atoms; at least one of R.sup.2 and
R.sup.6 represents an alkyl group having 1 to 6 carbon atoms; X
represents any one of a carbon atom and a nitrogen atom, the carbon
atom having any one of hydrogen and an alkyl group having 1 to 6
carbon atoms; the other of R.sup.2 and R.sup.6 represents hydrogen,
or one of R.sup.1 and R.sup.3 to R.sup.5 represents a substituted
or unsubstituted alkyl group having 1 to 6 carbon atoms; a dihedral
angle between a ring bonded to R.sup.1 and a phenyl group bonded to
R.sup.2 to R.sup.6 is greater than or equal to 30.degree. and less
than or equal to 90.degree.; and a dihedral angle between the ring
bonded to R.sup.1 and a ring of Ar is greater than or equal to
0.degree. and less than 2.degree..
2. The compound according to claim 1, wherein R.sup.1 represents
hydrogen.
3. The compound according to claim 1, wherein one of R.sup.2 and
R.sup.6 represents hydrogen.
4. A light-emitting device comprising the compound according to
claim 1.
5. A lighting device comprising the compound according to claim
4.
6. An electronic device comprising the light-emitting device
according to claim 4.
7. A compound represented by Formula (G5): ##STR00051## wherein:
R.sup.1 to R.sup.6 independently represent any one of hydrogen and
a substituted or unsubstituted alkyl group having 1 to 6 carbon
atoms; R.sup.7 to R.sup.9 each represent hydrogen; at least one of
R.sup.2 and R.sup.6 represents an alkyl group having 1 to 6 carbon
atoms; X represents any one of a carbon atom and a nitrogen atom,
the carbon atom having any one of hydrogen and an alkyl group
having 1 to 6 carbon atoms; L represents a monoanionic ligand; the
other of R.sup.2 and R.sup.6 represents hydrogen, or one of R.sup.1
and R.sup.3 to R.sup.5 represents a substituted or unsubstituted
alkyl group having 1 to 6 carbon atoms; a dihedral angle between a
ring bonded to R.sup.1 and a phenyl group bonded to R.sup.2 to
R.sup.6 is greater than or equal to 30.degree. and less than or
equal to 90.degree.; a dihedral angle between the ring bonded to
R.sup.1 and a phenyl group bonded to R.sup.7 to R.sup.9 is greater
than or equal to 0.degree. and less than 2.degree.; and a bond
angle denoted by a is greater than or equal to 120.degree. and less
than 129.degree..
8. The compound according to claim 7, wherein: the monoanionic
ligand is represented by any one of Formulae (L1) to (L7):
##STR00052## ##STR00053## R.sup.71 to R.sup.109 independently
represent any one of hydrogen, a substituted or unsubstituted alkyl
group having 1 to 6 carbon atoms, a halogen, a vinyl group, a
substituted or unsubstituted haloalkyl group having 1 to 6 carbon
atoms, a substituted or unsubstituted alkoxy group having 1 to 6
carbon atoms, and a substituted or unsubstituted alkylthio group
having 1 to 6 carbon atoms; A.sup.1 to A.sup.3 independently
represent any one of nitrogen and carbon bonded to hydrogen or to a
substituent R; and the substituent R is any one of an alkyl group
having 1 to 6 carbon atoms, a halogen, a haloalkyl group having 1
to 6 carbon atoms, and a phenyl group.
9. The compound according to claim 7, wherein R.sup.3 to R.sup.5
represent hydrogen.
10. The compound according to claim 7, wherein R.sup.1 represents
hydrogen.
11. The compound according to claim 7, wherein one of R.sup.2 and
R.sup.6 represents hydrogen.
12. A compound represented by Formula (G6): ##STR00054## wherein:
R.sup.1, R.sup.2 and R.sup.6 independently represent any one of
hydrogen and a substituted or unsubstituted alkyl group having 1 to
6 carbon atoms; R.sup.7 to R.sup.9 each represent hydrogen; one of
R.sup.2 and R.sup.6 represents an alkyl group having 1 to 6 carbon
atoms; the other one of R.sup.2 and R.sup.6 represents hydrogen; X
represents any one of a carbon atom and a nitrogen atom, the carbon
atom having any one of hydrogen and an alkyl group having 1 to 6
carbon atoms; L represents a monoanionic ligand; a dihedral angle
between a ring bonded to R.sup.1 and a phenyl group bonded to
R.sup.2 and R.sup.6 is greater than or equal to 30.degree. and less
than or equal to 90.degree.; a dihedral angle between the ring
bonded to R.sup.1 and a phenyl group bonded to R.sup.7 to R.sup.9
is greater than or equal to 0.degree. and less than 2.degree.; and
a bond angle denoted by a is greater than or equal to 120.degree.
and less than 129.degree..
13. The compound according to claim 12, wherein: the monoanionic
ligand is represented by any one of Formulae (L1) to (L7):
##STR00055## ##STR00056## R.sup.71 to R.sup.109 independently
represent any one of hydrogen, a substituted or unsubstituted alkyl
group having 1 to 6 carbon atoms, a halogen, a vinyl group, a
substituted or unsubstituted haloalkyl group having 1 to 6 carbon
atoms, a substituted or unsubstituted alkoxy group having 1 to 6
carbon atoms, and a substituted or unsubstituted alkylthio group
having 1 to 6 carbon atoms; A.sup.1 to A.sup.3 independently
represent any one of nitrogen and carbon bonded to hydrogen or to a
substituent R; and the substituent R is any one of an alkyl group
having 1 to 6 carbon atoms, a halogen, a haloalkyl group having 1
to 6 carbon atoms, and a phenyl group.
14. A light-emitting device comprising the compound according to
claim 12.
15. A lighting device comprising the compound according to claim
12.
16. An electronic device comprising the light-emitting device
according to claim 14.
Description
[0001] This application is a continuation of copending U.S.
application Ser. No. 14/482,536, filed on Sep. 10, 2014 which is
incorporated herein by reference.
TECHNICAL FIELD
[0002] The present invention relates to an object, a method, and a
manufacturing method. In addition, the present invention relates to
a process, a machine, manufacture, and a composition of matter. One
embodiment of the present invention relates to a semiconductor
device, a display device, a light-emitting device, a lighting
device, a driving method thereof, and a manufacturing method
thereof. One embodiment of the present invention relates to an
organometallic iridium complex. In particular, one embodiment of
the present invention relates to an organometallic iridium complex
that is capable of converting a triplet excited state into light.
In addition, one embodiment of the present invention relates to a
light-emitting element, a light-emitting device, an electronic
device, and a lighting device each including the organometallic
iridium complex.
BACKGROUND ART
[0003] In recent years, a light-emitting element using a
light-emitting organic compound or inorganic compound as a
light-emitting material has been actively developed. In particular,
a light-emitting element called an electroluminescence (EL) element
has attracted attention as a next-generation flat panel display
element because it has a simple structure in which a light-emitting
layer containing a light-emitting material is provided between
electrodes, and characteristics such as feasibility of being
thinner and more lightweight and responsive to input signals and
capability of driving with direct current at a low voltage. In
addition, a display using such a light-emitting element has a
feature that it is excellent in contrast and image quality, and has
a wide viewing angle. Further, since such a light-emitting element
is a plane light source, the light-emitting element is considered
applicable to a light source such as a backlight of a liquid
crystal display and an illumination device.
[0004] In the case where the light-emitting substance is an organic
compound having a light-emitting property, the emission mechanism
of the light-emitting element is a carrier-injection type.
Specifically, by applying a voltage with a light-emitting layer
provided between electrodes, electrons and holes injected from the
electrodes recombine to raise the light-emitting substance to an
excited state, and light is emitted when the substance in the
excited state returns to the ground state. There are two types of
the excited states which are possible: a singlet excited state (S*)
and a triplet excited state (T*). In addition, the statistical
generation ratio thereof in a light-emitting element is considered
to be S*:T*=1:3.
[0005] In general, the ground state of a light-emitting organic
compound is a singlet state. Light emission from a singlet excited
state (S*) is referred to as fluorescence where electron transition
occurs between the same multiplicities. In contrast, light emission
from a triplet excited state (T*) is referred to as phosphorescence
where electron transition occurs between different multiplicities.
Here, in a compound emitting fluorescence (hereinafter referred to
as a fluorescent compound), in general, phosphorescence cannot
observed at room temperature, and only fluorescence can be
observed. Accordingly, the internal quantum efficiency (the ratio
of generated photons to injected carriers) in a light-emitting
element using a fluorescent compound is assumed to have a
theoretical limit of 25% based on S*:T*=1:3.
[0006] In contrast, the use of a phosphorescent compound can
increase the internal quantum efficiency to 100% in theory. In
other words, emission efficiency can be 4 times as much as that of
the fluorescent compound. For these reasons, in order to obtain a
highly efficient light-emitting element, a light-emitting element
using a phosphorescent compound has been developed actively
recently. As the phosphorescent compound, an organometallic complex
that has iridium or the like as a central metal have particularly
attracted attention because of their high phosphorescence quantum
yield (for example, see Patent Documents 1 to 4).
[0007] Specifically, Patent Document 4 discloses an organometallic
complex that has a 4-arylpyrimidine derivative as a ligand and
iridium as a central metal.
REFERENCE
Patent Document
[Patent Document 1] Japanese Published Patent Application No.
2007-137872
[Patent Document 2] Japanese Published Patent Application No.
2008-069221
[Patent Document 3] PCT International Publication No.
2008-035664
[Patent Document 4] Japanese Published Patent Application No.
2012-149030
DISCLOSURE OF INVENTION
[0008] Although phosphorescent materials exhibiting various
emission colors have been actively developed as disclosed in Patent
Documents 1 to 4, development of novel materials with higher
efficiency or a longer lifetime has been demanded.
[0009] The organometallic complex disclosed in Patent Document 4
has particularly excellent characteristics. For example, when the
4-arylpyrimidine derivative has a phenyl group at the 6-position,
the transition dipole moment becomes stronger and the oscillator
strength becomes larger. Such large oscillator strength leads to,
for example, higher efficiency of energy transfer from a host
material to the organometallic complex, so that highly efficient
light emission can be achieved. However, depending on the
substituent and its position, .pi.-conjugation in the
organometallic complex extends, which means that even if highly
efficient light emission is achieved, the emission wavelength
becomes long in some cases. When the emission wavelength becomes
long, the organometallic complex emits light having a low
luminosity factor.
[0010] In view of the above, an object of one embodiment of the
present invention is to provide an organometallic iridium complex
with high emission efficiency and a long lifetime. An object of one
embodiment of the present invention is to provide an organometallic
iridium complex in which .pi.-conjugation does not easily extend
and which has high emission efficiency. An object of one embodiment
of the present invention is to provide an organometallic iridium
complex that emits light having a high luminosity factor at high
efficiency. An object of one embodiment of the present invention is
to provide a novel organometallic iridium complex. An object of one
embodiment of the present invention is to provide a light-emitting
element, a light-emitting device, an electronic device, or a
lighting device having high emission efficiency. An object of one
embodiment of the present invention is to provide a novel
light-emitting element and a novel light-emitting device.
[0011] Note that the descriptions of these objects do not disturb
the existence of other objects. In one embodiment of the present
invention, there is no need to achieve all the objects. Other
objects will be apparent from and can be derived from the
description of the specification, the drawings, the claims, and the
like.
[0012] One embodiment of the present invention is an organometallic
iridium complex including a structure represented by General
Formula (G1).
##STR00002##
[0013] In General Formula (G1), Ar represents a substituted or
unsubstituted arylene group having 6 to 13 carbon atoms. R.sup.1 to
R.sup.6 independently represent any one of hydrogen and a
substituted or unsubstituted alkyl group having 1 to 6 carbon
atoms. Note that at least one of R.sup.2 and R.sup.6 represents an
alkyl group having 1 to 6 carbon atoms. X represents any one of a
carbon atom and a nitrogen atom, and the carbon atom has any one of
hydrogen and an alkyl group having 1 to 6 carbon atoms. A dihedral
angle between a pyridine ring and a phenyl group having R.sup.2 to
R.sup.6, or a dihedral angle between a pyrimidine ring and the
phenyl group having R.sup.2 to R.sup.6 is greater than or equal to
30.degree. and less than or equal to 90.degree.. An interior angle
of the pyridine ring facing R.sup.1 or an interior angle of the
pyrimidine ring facing R.sup.1 is within a range of .+-.2.degree.
of 120.degree..
[0014] Another embodiment of the present invention is an
organometallic iridium complex represented by General Formula
(G2).
##STR00003##
[0015] In General Formula (G2), R.sup.1 to R.sup.9 independently
represent any one of hydrogen and a substituted or unsubstituted
alkyl group having 1 to 6 carbon atoms. Note that at least one of
R.sup.2 and R.sup.6 represents an alkyl group having 1 to 6 carbon
atoms. X represents any one of a carbon atom and a nitrogen atom,
and the carbon atom has any one of hydrogen and an alkyl group
having 1 to 6 carbon atoms. Further, L represents a monoanionic
ligand. A dihedral angle between a pyridine ring and a phenyl group
having R.sup.7 to R.sup.9, or a dihedral angle between a pyrimidine
ring and the phenyl group having R.sup.7 to R.sup.9 is greater than
or equal to 0.degree. and less than 2.degree.. A dihedral angle
between the pyridine ring and a phenyl group having R.sup.2 to
R.sup.6, or a dihedral angle between the pyrimidine ring and the
phenyl group having R.sup.2 to R.sup.6 is greater than or equal to
30.degree. and less than or equal to 90.degree..
[0016] Another embodiment of the present invention is an
organometallic iridium complex represented by General Formula
(G3).
##STR00004##
[0017] In General Formula (G3), R.sup.1, R.sup.2, and R.sup.6 to
R.sup.9 independently represent any one of hydrogen and a
substituted or unsubstituted alkyl group having 1 to 6 carbon
atoms. Note that at least one of R.sup.2 and R.sup.6 represents an
alkyl group having 1 to 6 carbon atoms. X represents any one of a
carbon atom and a nitrogen atom, and the carbon atom has any one of
hydrogen and an alkyl group having 1 to 6 carbon atoms. Further, L
represents a monoanionic ligand. A dihedral angle between a
pyridine ring and a phenyl group having R.sup.7 to R.sup.9, or a
dihedral angle between a pyrimidine ring and the phenyl group
having R.sup.7 to R.sup.9 is greater than or equal to 0.degree. and
less than 2.degree.. A dihedral angle between the pyridine ring and
a phenyl group having R.sup.2 and R.sup.6, or a dihedral angle
between the pyrimidine ring and the phenyl group having R.sup.2 and
R.sup.6 is greater than or equal to 30.degree. and less than or
equal to 90.degree..
[0018] Another embodiment of the present invention is an
organometallic iridium complex represented by General Formula
(G4).
##STR00005##
[0019] In General Formula (G4), R.sup.1, R.sup.2, and R.sup.6 to
R.sup.9 independently represent any one of hydrogen and a
substituted or unsubstituted alkyl group having 1 to 6 carbon
atoms. Note that at least one of R.sup.2 and R.sup.6 represents an
alkyl group having 1 to 6 carbon atoms. X represents any one of a
carbon atom and a nitrogen atom, and the carbon atom has any one of
hydrogen and an alkyl group having 1 to 6 carbon atoms. A dihedral
angle between a pyridine ring and a phenyl group having R.sup.7 to
R.sup.9, or a dihedral angle between a pyrimidine ring and the
phenyl group having R.sup.7 to R.sup.9 is greater than or equal to
0.degree. and less than 2.degree.. A dihedral angle between the
pyridine ring and a phenyl group having R.sup.2 and R.sup.6, or a
dihedral angle between the pyrimidine ring and the phenyl group
having R.sup.2 and R.sup.6 is greater than or equal to 30.degree.
and less than or equal to 90.degree..
[0020] Another embodiment of the present invention is an
organometallic iridium complex represented by General Formula
(G5).
##STR00006##
[0021] In General Formula (G5), R.sup.1 to R.sup.9 independently
represent any one of hydrogen and a substituted or unsubstituted
alkyl group having 1 to 6 carbon atoms. Note that at least one of
R.sup.2 and R.sup.6 represents an alkyl group having 1 to 6 carbon
atoms. X represents any one of a carbon atom and a nitrogen atom,
and the carbon atom has any one of hydrogen and an alkyl group
having 1 to 6 carbon atoms. Further, L represents a monoanionic
ligand. A bond angle denoted by .alpha. in the formula is greater
than or equal to 120.degree. and less than 129.degree.. A dihedral
angle between a pyridine ring and a phenyl group having R.sup.2 to
R.sup.6, or a dihedral angle between a pyrimidine ring and the
phenyl group having R.sup.2 to R.sup.6 is greater than or equal to
30.degree. and less than or equal to 90.degree..
[0022] Another embodiment of the present invention is an
organometallic iridium complex represented by General Formula
(G6).
##STR00007##
[0023] In General Formula (G6), R.sup.1, R.sup.2 and R.sup.6 to
R.sup.9 independently represent any one of hydrogen and a
substituted or unsubstituted alkyl group having 1 to 6 carbon
atoms. Note that at least one of R.sup.2 and R.sup.6 represents an
alkyl group having 1 to 6 carbon atoms. X represents any one of a
carbon atom and a nitrogen atom, and the carbon atom has any one of
hydrogen and an alkyl group having 1 to 6 carbon atoms. Further, L
represents a monoanionic ligand. A bond angle denoted by .alpha. in
the formula is greater than or equal to 120.degree. and less than
129.degree.. A dihedral angle between a pyridine ring and a phenyl
group having R.sup.2 and R.sup.6, or a dihedral angle between a
pyrimidine ring and the phenyl group having R.sup.2 and R.sup.6 is
greater than or equal to 30.degree. and less than or equal to
90.degree..
[0024] Another embodiment of the present invention is an
organometallic iridium complex represented by General Formula
(G7).
##STR00008##
[0025] In General Formula (G7), R.sup.1, R.sup.2 and R.sup.6 to
R.sup.9 independently represent any one of hydrogen and a
substituted or unsubstituted alkyl group having 1 to 6 carbon
atoms. Note that at least one of R.sup.2 and R.sup.6 represents an
alkyl group having 1 to 6 carbon atoms. X represents any one of a
carbon atom and a nitrogen atom, and the carbon atom has any one of
hydrogen and an alkyl group having 1 to 6 carbon atoms. A bond
angle denoted by .alpha. in the formula is greater than or equal to
120.degree. and less than 129.degree.. A dihedral angle between a
pyridine ring and a phenyl group having R.sup.2 and R.sup.6, or a
dihedral angle between a pyrimidine ring and the phenyl group
having R.sup.2 and R.sup.6 is greater than or equal to 30.degree.
and less than or equal to 90.degree..
[0026] In addition, in the above-described structures, the
monoanionic ligand is preferably a ligand represented by any one of
General Formulae (L1) to (L7).
##STR00009## ##STR00010##
[0027] In General Formulae (L1) to (L7), R.sup.71 to R.sup.109
independently represent any one of hydrogen, a substituted or
unsubstituted alkyl group having 1 to 6 carbon atoms, a halogen, a
vinyl group, a substituted or unsubstituted haloalkyl group having
1 to 6 carbon atoms, a substituted or unsubstituted alkoxy group
having 1 to 6 carbon atoms, and a substituted or unsubstituted
alkylthio group having 1 to 6 carbon atoms. In addition, A.sup.1 to
A.sup.3 independently represent any one of nitrogen and carbon
bonded to hydrogen or to a substituent R. The substituent R is any
one of an alkyl group having 1 to 6 carbon atoms, a halogen, a
haloalkyl group having 1 to 6 carbon atoms, and a phenyl group.
[0028] One embodiment of the present invention is a light-emitting
element including, between a pair of electrodes, any of the
organometallic iridium complexes described above. In particular,
any of the organometallic iridium complexes described above is
preferably contained in a light-emitting layer.
[0029] Other embodiments of the present invention are a
light-emitting device, an electronic device, and a lighting device
each of which includes the above light-emitting element.
[0030] In one embodiment of the present invention, an
organometallic iridium complex with high emission efficiency and a
long lifetime can be provided. An organometallic iridium complex in
which .pi.-conjugation does not easily extend and which has high
emission efficiency can be provided. An organometallic iridium
complex that emits light having a high luminosity factor at high
efficiency can be provided. A light-emitting element, a
light-emitting device, an electronic device, or a lighting device
having high emission efficiency can be provided.
[0031] Note that one embodiment of the present invention is not
limited to the above effects. For example, depending on
circumstances or conditions, one embodiment of the present
invention might produce another effect. Furthermore, depending on
circumstances or conditions, one embodiment of the present
invention might not produce any of the above effects.
BRIEF DESCRIPTION OF DRAWINGS
[0032] FIG. 1 illustrates models of atomic arrangement used for
calculation.
[0033] FIG. 2 shows calculation results of a dihedral angle between
a pyrimidine ring and a phenyl group.
[0034] FIG. 3 illustrates a structure of a light-emitting
element.
[0035] FIG. 4 illustrates a structure of a light-emitting
element.
[0036] FIGS. 5A and 5B each illustrate a structure of a
light-emitting element.
[0037] FIGS. 6A and 6B illustrate a light-emitting device.
[0038] FIGS. 7A to 7D each illustrate an electronic device.
[0039] FIGS. 8A to 8C illustrate lighting devices and an electronic
device.
[0040] FIG. 9 is a .sup.1H-NMR chart of an organometallic iridium
complex represented by Structural Formula (100).
[0041] FIG. 10 shows an ultraviolet-visible absorption spectrum and
an emission spectrum of an organometallic iridium complex
represented by Structural Formula (100).
[0042] FIG. 11 illustrates a light-emitting element.
[0043] FIG. 12 shows voltage-luminance characteristics of a
light-emitting element 1, a comparative light-emitting element 2,
and a comparative light-emitting element 3.
[0044] FIG. 13 shows luminance-current efficiency characteristics
of a light-emitting element 1, a comparative light-emitting element
2, and a comparative light-emitting element 3.
[0045] FIG. 14 shows voltage-current characteristics of a
light-emitting element 1, a comparative light-emitting element 2,
and a comparative light-emitting element 3.
[0046] FIG. 15 shows luminance-external quantum efficiency
characteristics of a light-emitting element 1, a comparative
light-emitting element 2, and a comparative light-emitting element
3.
[0047] FIG. 16 shows emission spectra of a light-emitting element
1, a comparative light-emitting element 2, and a comparative
light-emitting element 3.
[0048] FIG. 17 shows a .sup.1H-NMR chart of an organometallic
iridium complex represented by Structural Formula (134).
[0049] FIG. 18 shows an ultraviolet-visible absorption spectrum and
an emission spectrum of an organometallic iridium complex
represented by Structural Formula (134).
BEST MODE FOR CARRYING OUT THE INVENTION
[0050] Embodiments will be described in detail with reference to
drawings. Note that the present invention is not limited to the
description below, and it is easily understood by those skilled in
the art that various changes and modifications can be made without
departing from the spirit and scope of the present invention. Thus,
the present invention should not be interpreted as being limited to
the content of the embodiments below. Note that in the structures
of the invention described below, the same portions or portions
having similar functions are denoted by the same reference numerals
in different drawings, and description of such portions is not
repeated.
[0051] A top-emission structure, a bottom-emission structure, and a
dual-emission structure can be applied to the light-emitting
elements described in the present specification.
[0052] In the present specification and the like, a dihedral angle
and a bond angle in a molecular structure of an organometallic
iridium complex are values calculated using a quantum chemistry
calculation program produced by Gaussian, Inc. When another quantum
chemistry calculation program is used to calculate the molecular
structure of the organometallic iridium complex of one embodiment
of the present invention, the calculated value is sometimes
different from that obtained by using the above quantum chemistry
calculation program produced by Gaussian, Inc. A calculated value
might also be influenced by the calculation conditions of the
quantum chemistry calculation program.
[0053] The light-emitting device in this specification and the like
includes, in its category, an image display device and a light
source. The light-emitting device includes the following modules in
its category: a module in which a connector, such as a flexible
printed circuit (FPC) or a tape carrier package (TCP), is attached
to a panel, a module in which a printed wiring board is provided at
the end of a TCP, and a module in which an integrated circuit (IC)
is directly mounted on a light-emitting element by a chip-on-glass
(COG) method.
Embodiment 1
[0054] In this embodiment, organometallic iridium complexes which
are embodiments of the present invention are described.
[0055] One embodiment of the present invention is an organometallic
iridium complex including a structure represented by General
Formula (G1).
##STR00011##
[0056] In General Formula (G1), Ar represents a substituted or
unsubstituted arylene group having 6 to 13 carbon atoms. R.sup.1 to
R.sup.6 independently represent any one of hydrogen and a
substituted or unsubstituted alkyl group having 1 to 6 carbon
atoms. Note that at least one of R.sup.2 and R.sup.6 represents an
alkyl group having 1 to 6 carbon atoms. X represents any one of a
carbon atom and a nitrogen atom, and the carbon atom has any one of
hydrogen and an alkyl group having 1 to 6 carbon atoms. A dihedral
angle between a pyridine ring and a phenyl group having R.sup.2 to
R.sup.6, or a dihedral angle between a pyrimidine ring and the
phenyl group having R.sup.2 to R.sup.6 is greater than or equal to
30.degree. and less than or equal to 90.degree.. An interior angle
of the pyridine ring facing R.sup.1 or an interior angle of the
pyrimidine ring facing R.sup.1 is within a range of .+-.2.degree.
of 120.degree..
[0057] One embodiment of the present invention is an organometallic
iridium complex represented by General Formula (G2).
##STR00012##
[0058] In General Formula (G2), R.sup.1 to R.sup.9 independently
represent any one of hydrogen and a substituted or unsubstituted
alkyl group having 1 to 6 carbon atoms. Note that at least one of
R.sup.2 and R.sup.6 represents an alkyl group having 1 to 6 carbon
atoms. X represents any one of a carbon atom and a nitrogen atom,
and the carbon atom has any one of hydrogen and an alkyl group
having 1 to 6 carbon atoms. Further, L represents a monoanionic
ligand. A dihedral angle between a pyridine ring and a phenyl group
having R.sup.7 to R.sup.9, or a dihedral angle between a pyrimidine
ring and the phenyl group having R.sup.7 to R.sup.9 is greater than
or equal to 0.degree. and less than 2.degree.. A dihedral angle
between the pyridine ring and a phenyl group having R.sup.2 to
R.sup.6, or a dihedral angle between the pyrimidine ring and the
phenyl group having R.sup.2 to R.sup.6 is greater than or equal to
30.degree. and less than or equal to 90.degree..
[0059] As described with reference to General Formula (G1) or (G2),
one embodiment of the present invention is technically
characterized by a dihedral angle between the pyridine ring or the
pyrimidine ring and the phenyl group that is bonded to the pyridine
ring or the pyrimidine ring in the molecular structure of the
organometallic iridium complex. Since the dihedral angle between
the pyridine ring or the pyrimidine ring and the phenyl group that
is bonded to the pyridine ring or the pyrimidine ring is in the
predetermined range, it is possible to provide an organometallic
iridium complex with high emission efficiency and a long lifetime,
an organometallic iridium complex in which .pi.-conjugation does
not easily extend and which has high emission efficiency, or an
organometallic iridium complex that emits light having a high
luminosity factor at high efficiency.
[0060] Here, from a dihedral angle between a pyridine ring or a
pyrimidine ring and a phenyl group bonded to the pyridine or
pyrimidine ring in the molecular structure of an organometallic
iridium complex, the triplet excited level of the organometallic
iridium complex was calculated. Specifically, the triplet level of
(acetylacetonato)bis(4,6-diphenylpyrimidinato)iridium(III)
(abbreviation: Ir(dppm).sub.2(acac)) represented by Structural
Formula (500) was calculated from the dihedral angle between the
pyrimidine ring and the phenyl group at the 6-position of the
pyrimidine ring.
##STR00013##
[0061] FIG. 1 shows model diagrams of atomic arrangement used for
the calculation. The model diagrams in FIG. 1 schematically
illustrate atomic arrangement of a part of Ir(dppm).sub.2(acac),
and are ones for explaining the dihedral angle between the
pyrimidine ring (Pm) and the phenyl group (Ph) at the 6-position of
the pyrimidine ring.
[0062] In the model diagram in the upper part of FIG. 1, the
dihedral angle (.beta.) between the pyrimidine ring (Pm) and the
phenyl group (Ph) at the 6-position of the pyrimidine ring is
0.degree.. The dihedral angle (.beta.) was increased as shown in
the lower part of FIG. 1, and the triplet levels of the
organometallic iridium complex were calculated. Note that the
dihedral angle between the pyrimidine ring (Pm) and the phenyl
group at the 6-position of the pyrimidine ring in
Ir(dppm).sub.2(acac) was changed from 0.degree. to 90.degree. at a
step interval of 10.degree.. In FIG. 1, the kinds of the atoms (an
iridium atom (Ir), a carbon atom (C), a hydrogen atom (H), a
nitrogen atom (N), and an oxygen atom (O)) are shown in the box
bounded by the dashed line.
[0063] The calculating method is as follows. Note that Gaussian 09
was used as the quantum chemistry calculation program. A high
performance computer (Altix 4700, manufactured by SGI Japan, Ltd.)
was used for the calculations.
[0064] As basis functions, 6-311G(d,p) was used for H, C, N, and O,
and Lanl2dz was used for Ir. As a functional, B3PW91 was used. The
triplet level was worked out by TD-DFT calculation of singlet and
triplet excited states. The results of calculation are shown in
FIG. 2.
[0065] As shown by the results in FIG. 2, when the dihedral angle
between the pyrimidine ring and the phenyl group at the 6-position
of the pyrimidine ring in Ir(dppm).sub.2(acac) is 0.degree., the
triplet excitation energy equivalent to a wavelength of 547 nm, and
when the dihedral angle is 30.degree., the triplet excitation
energy equivalent to a wavelength of 542 nm. When the dihedral
angle between the pyrimidine ring and the phenyl group at the
6-position of the pyrimidine ring is 90.degree., the triplet
excitation energy equivalent to a wavelength of 517 nm. FIG. 2
shows the results of calculation using dihedral angles from
0.degree. to 90.degree. at a step interval of 10.degree.. In
Ir(dppm).sub.2(acac) represented by Structural Formula (500), the
dihedral angle between the pyrimidine ring and the phenyl group at
the 6-position of the pyrimidine ring was found to be 18.degree. by
calculation. In FIG. 2, triplet excitation energy is converted into
a wavelength (nm).
[0066] The calculation results in FIG. 2 suggest that in the case
where the dihedral angle between the pyrimidine ring and the phenyl
group at the 6-position of the pyrimidine ring in the
organometallic iridium complex is greater than or equal to
30.degree. and less than or equal to 90.degree., the emission
wavelength becomes shorter than that in the case where the dihedral
angle between the pyrimidine ring and the phenyl group at the
6-position of the pyrimidine ring in the organometallic iridium
complex is 0.degree., by greater than or equal to 5 nm and less
than or equal to 30 nm.
[0067] When the dihedral angle between the pyrimidine ring and the
phenyl group at the 6-position of the pyrimidine ring in the
organometallic iridium complex is increased in the above manner,
i.e., when the phenyl group at the 6-position of the pyrimidine
ring in the organometallic iridium complex is twisted,
.pi.-conjugation does not easily extend, and the emission
wavelength decreases by approximately 30 nm at the maximum. In this
manner, the emission wavelength of the organometallic iridium
complex depends on the dihedral angle formed by a substituent
bonded to the pyridine ring or the pyrimidine ring (here, the
dihedral angle formed by the phenyl group at the 6-position of the
pyrimidine ring) in the organometallic iridium complex.
[0068] Note that in the model diagrams in FIG. 1, in order that the
dihedral angle formed by the phenyl group at the 6-position of the
pyrimidine ring in the organometallic iridium complex can be
changed, no substituent is bonded to the pyrimidine ring or the
phenyl group bonded to the 6-position of the pyrimidine ring. In an
actual organometallic iridium complex, bonding of a substituent to
the pyridine or pyrimidine ring or the phenyl group bonded to the
pyridine or pyrimidine ring can change the dihedral angle between
the pyridine or pyrimidine ring and the phenyl group bonded to the
pyridine or pyrimidine ring in the molecular structure of the
organometallic iridium complex. However, depending on a
substituent, the pyridine ring or the pyrimidine ring might be
distorted.
[0069] Here, bond angles and a dihedral angle in each of
organometallic iridium complexes represented by Structural Formulae
(501), (500), (100), (502), (503), and (504) were calculated.
##STR00014## ##STR00015##
[0070] Note that the organometallic iridium complex represented by
Structural Formula (501) is
bis(2-phenylpyridinato-N,C.sup.2')irridium(III) acetylacetonate
(abbreviation: Ir(ppy).sub.2(acac)). The organometallic iridium
complex represented by Structural Formula (500) is
Ir(dppm).sub.2(acac). The organometallic iridium complex
represented by Structural Formula (100) is
bis{2-[6-(2,6-dimethylphenyl)-4-pyrimidinyl-.kappa.N3]phenyl-.kappa.C}(2,-
4-pentanedionato-.kappa.O,O') iridium(III) (abbreviation:
Ir(ppm-dmp).sub.2(acac)). The organometallic iridium complex
represented by Structural Formula (502) is
(acetylacetonato)bis[5-methyl-6-(2-methylphenyl)-4-phenylpyrimidinato]iri-
dium(III) (another name:
bis{2-[5-methyl-6-(2-methylphenyl)-4-pyrimidinyl-.kappa.N3]phenyl-.kappa.-
C}(2,4-pentanedionato-.kappa..sup.2O,O')iridium(III))
(abbreviation: Ir(mpmppm).sub.2(acac)). The organometallic iridium
complex represented by Structural Formula (503) is
(acetylacetonato)bis(4,5,6-triphenylpyrimidinato)iridium(III)
(another name:
bis[2-(5,6-diphenyl-4-pyrimidinyl-.kappa.N3)phenyl-.kappa.C](2,4-pe-
ntanedionato-.kappa..sup.2O,O')iridium(III)) (abbreviation:
Ir(tppm).sub.2(acac)). The organometallic iridium complex
represented by Structural Formula (504) is
bis[2-(5-phenyl-4-pyrimidinyl-.kappa.N3)phenyl-.kappa.C](2,4-pentanediona-
to-.kappa..sup.2O,O')iridium(III) (abbreviation: Ir(5
dppm).sub.2(acac)).
[0071] The calculating method is as follows. Note that Gaussian 09
was used as the quantum chemistry calculation program. A high
performance computer (Altix 4700, manufactured by SGI Japan, Ltd.)
was used for the calculations.
[0072] As basis functions, 6-311G(d,p) was used for H, C, N, and O,
and Lanl2dz was used for Ir. As a functional, B3PW91 was used.
[0073] As the bond angle and the dihedral angle in the
organometallic iridium complexes represented by Structural Formulae
(501), (500), (100), (502), (503), and (504), bond angles
.alpha..sub.1 and .alpha..sub.2, an interior angle .alpha..sub.3,
and a dihedral angle .beta..sub.2 of a molecular structure
represented by Structural Formula (600) were calculated. The
organometallic iridium complexes represented by Structural Formulae
(501), (500), (100), (502), (503), and (504) have the molecular
structure represented by Structural Formula (600) in common.
##STR00016##
[0074] Note that in Structural Formula (600), a bond angle denoted
by .alpha..sub.1 is the exterior angle of the phenyl group at the
2-position of the pyridine ring; a bond angle denoted by
.alpha..sub.2 is the exterior angle at the 2-position of the
pyridine ring; .alpha..sub.3 denotes the interior angle at the
3-position of the pyridine ring; and .beta..sub.2 denotes the
dihedral angle between the pyridine ring and the phenyl group at
the 2-position of the pyridine ring. Note that although a pyridine
ring is used for description of the bond angles .alpha..sub.1 and
.alpha..sub.2, the interior angle .alpha..sub.3, and the dihedral
angle .beta..sub.2 in Structural Formula (600) for easy
understanding, it is also possible to apply the bond angles
.alpha..sub.1 and .alpha..sub.2, the interior angle .alpha..sub.3,
and the dihedral angle .beta..sub.2 to a pyrimidine ring. Note that
in the case of a pyrimidine ring, the site of substitution of a
phenyl group is the 4-position of the pyrimidine ring.
[0075] The results of calculation are shown in Table 1.
TABLE-US-00001 TABLE 1 Structural formula (501) (500) (100) (502)
(503) (504) Angle .alpha..sub.1 (.degree.) 123.6 123.5 123.5 125.6
125.3 124.7 Angle .alpha..sub.2 (.degree.) 126.5 127.4 127.6 129.6
129.8 129.7 Angle .alpha..sub.3 (.degree.) 120.2 119.3 119.1 117.0
117.6 116.9 Dihedral 0.13 0.48 0.56 2.98 6.10 4.66 angle
.beta..sub.2 (.degree.)
[0076] As shown in Table 1, in Structural Formulae (501), (500),
and (100), the angle .alpha..sub.1 is greater than or equal to
120.degree. and less than 124.degree.. In Structural Formulae
(502), (503), and (504), the angle .alpha..sub.1 is greater than or
equal to 124.degree.. In Structural Formulae (501), (500), and
(100), the angle .alpha..sub.2 is greater than or equal to
120.degree. and less than 129.degree.. In Structural Formulae
(502), (503), and (504), the angle .alpha..sub.2 is greater than or
equal to 129.degree.. In Structural Formulae (501), (500), and
(100), the angle .alpha..sub.3 is within a range of .+-.2.degree.
of 120.degree., while the angle .alpha..sub.3 is outside the range
of .+-.2.degree. of 120.degree. in Structural Formulae (502),
(503), and (504). In Structural Formulae (501), (500), and (100),
the dihedral angle .beta..sub.2 is greater than or equal to
0.degree. and less than or equal to 2.degree., while the dihedral
angle .beta..sub.2 is greater than or equal to 2.degree. in
Structural Formulae (502), (503), and (504).
[0077] As described above, depending on the position or the kind of
a substituent bonded to the pyridine ring or the pyrimidine ring,
the shape of the pyridine ring or the pyrimidine ring is changed.
In other words, the molecular structure of the pyridine ring or the
pyrimidine ring is distorted. As shown in Table 1, in the
organometallic iridium complexes represented by Structural Formulae
(501), (500), and (100), the molecular structure distortion of the
pyridine ring or the pyrimidine ring is extremely small. Meanwhile,
in each of the organometallic iridium complexes represented by
Structural Formulae (502), (503), and (504), the molecular
structure distortion of the pyridine ring or the pyrimidine ring is
large. Molecular structure distortion of the pyridine ring or the
pyrimidine ring can be found by calculating any one of the angles
.alpha..sub.1 to .alpha..sub.3 and the dihedral angle .beta..sub.2
as shown in Table 1. Note that when molecular structure distortion
of the pyridine ring or the pyrimidine ring is large, the quantum
efficiency cannot be high in some cases.
[0078] In view of the above, in one embodiment of the present
invention, the phenyl group is bonded at the predetermined position
of the pyridine ring or the pyrimidine ring in the organometallic
iridium complex as illustrated in General Formula (G1) or (G2).
Furthermore, in the organometallic iridium complex, the dihedral
angle formed by the phenyl group bonded to the pyridine ring or the
pyrimidine ring is within the predetermined range. Extension of
.pi.-conjugation is thus inhibited and the wavelength of light
emitted from the organometallic iridium complex becomes shorter.
Moreover, molecular structure distortion of the pyridine ring or
the pyrimidine ring is inhibited, whereby high quantum efficiency
can be achieved.
[0079] The structure of an organometallic iridium complex of one
embodiment of the present invention can be represented by not only
General Formulae (G1) and (G2) but also the formulae that are shown
below.
[0080] One embodiment of the present invention is an organometallic
iridium complex represented by General Formula (G3).
##STR00017##
[0081] In General Formula (G3), R.sup.1, R.sup.2, and R.sup.6 to
R.sup.9 independently represent any one of hydrogen and a
substituted or unsubstituted alkyl group having 1 to 6 carbon
atoms. Note that at least one of R.sup.2 and R.sup.6 represents an
alkyl group having 1 to 6 carbon atoms. X represents any one of a
carbon atom and a nitrogen atom, and the carbon atom has any one of
hydrogen and an alkyl group having 1 to 6 carbon atoms. Further, L
represents a monoanionic ligand. A dihedral angle between a
pyridine ring and a phenyl group having R.sup.7 to R.sup.9, or a
dihedral angle between a pyrimidine ring and the phenyl group
having R.sup.7 to R.sup.9 is greater than or equal to 0.degree. and
less than 2.degree.. A dihedral angle between the pyridine ring and
a phenyl group having R.sup.2 and R.sup.6, or a dihedral angle
between the pyrimidine ring and the phenyl group having R.sup.2 and
R.sup.6 is greater than or equal to 30.degree. and less than or
equal to 90.degree..
[0082] One embodiment of the present invention is an organometallic
iridium complex represented by General Formula (G4).
##STR00018##
[0083] In General Formula (G4), R.sup.2, and R.sup.6 to R.sup.9
independently represent any one of hydrogen and a substituted or
unsubstituted alkyl group having 1 to 6 carbon atoms. Note that at
least one of R.sup.2 and R.sup.6 represents an alkyl group having 1
to 6 carbon atoms. X represents any one of a carbon atom and a
nitrogen atom, and the carbon atom has any one of hydrogen and an
alkyl group having 1 to 6 carbon atoms. A dihedral angle between a
pyridine ring and a phenyl group having R.sup.7 to R.sup.9, or a
dihedral angle between a pyrimidine ring and the phenyl group
having R.sup.7 to R.sup.9 is greater than or equal to 0.degree. and
less than 2.degree.. A dihedral angle between the pyridine ring and
a phenyl group having R.sup.2 and R.sup.6, or a dihedral angle
between the pyrimidine ring and the phenyl group having R.sup.2 and
R.sup.6 is greater than or equal to 30.degree. and less than or
equal to 90.degree..
[0084] One embodiment of the present invention is an organometallic
iridium complex represented by General Formula (G5).
##STR00019##
[0085] In General Formula (G5), R.sup.1 to R.sup.9 independently
represent any one of hydrogen and a substituted or unsubstituted
alkyl group having 1 to 6 carbon atoms. Note that at least one of
R.sup.2 and R.sup.6 represents an alkyl group having 1 to 6 carbon
atoms. X represents any one of a carbon atom and a nitrogen atom,
and the carbon atom has any one of hydrogen and an alkyl group
having 1 to 6 carbon atoms. Further, L represents a monoanionic
ligand. A bond angle denoted by .alpha. is greater than or equal to
120.degree. and less than 129.degree.. A dihedral angle between a
pyridine ring and a phenyl group having R.sup.2 to R.sup.6, or a
dihedral angle between a pyrimidine ring and the phenyl group
having R.sup.2 to R.sup.6 is greater than or equal to 30.degree.
and less than or equal to 90.degree..
[0086] One embodiment of the present invention is an organometallic
iridium complex represented by General Formula (G6).
##STR00020##
[0087] In General Formula (G6), R.sup.1, R.sup.2 and R.sup.6 to
R.sup.9 independently represent any one of hydrogen and a
substituted or unsubstituted alkyl group having 1 to 6 carbon
atoms. Note that at least one of R.sup.2 and R.sup.6 represents an
alkyl group having 1 to 6 carbon atoms. X represents any one of a
carbon atom and a nitrogen atom, and the carbon atom has any one of
hydrogen and an alkyl group having 1 to 6 carbon atoms. Further, L
represents a monoanionic ligand. A bond angle denoted by .alpha. in
the formula is greater than or equal to 120.degree. and less than
129.degree.. A dihedral angle between a pyridine ring and a phenyl
group having R.sup.2 and R.sup.6, or a dihedral angle between a
pyrimidine ring and the phenyl group having R.sup.2 and R.sup.6 is
greater than or equal to 30.degree. and less than or equal to
90.degree..
[0088] One embodiment of the present invention is an organometallic
iridium complex represented by General Formula (G7).
##STR00021##
[0089] In General Formula (G7), R.sup.1, R.sup.2 and R.sup.6 to
R.sup.9 independently represent any one of hydrogen and a
substituted or unsubstituted alkyl group having 1 to 6 carbon
atoms. Note that at least one of R.sup.2 and R.sup.6 represents an
alkyl group having 1 to 6 carbon atoms. X represents any one of a
carbon atom and a nitrogen atom, and the carbon atom has any one of
hydrogen and an alkyl group having 1 to 6 carbon atoms. A bond
angle denoted by .alpha. in the formula is greater than or equal to
120.degree. and less than 129.degree.. A dihedral angle between a
pyridine ring and a phenyl group having R.sup.2 and R.sup.6, or a
dihedral angle between a pyrimidine ring and the phenyl group
having R.sup.2 and R.sup.6 is greater than or equal to 30.degree.
and less than or equal to 90.degree..
[0090] In each of General Formulae (G1) to (G7), it is preferable
that at least one of R.sup.2 and R.sup.6, further preferably both
of them, represent an alkyl group. With this structure, a broad
electron distribution caused by a conjugated bond between the
pyridine or pyrimidine ring and the phenyl group can be prevented.
In a structure in which both of R.sup.2 and R.sup.6 represent alkyl
groups, the dihedral angle between the pyridine or pyrimidine ring
and the phenyl group having R.sup.2 and R.sup.6 can be large.
[0091] When the interior angle of the pyridine ring facing R.sup.1,
or the interior angle of the pyrimidine ring facing R.sup.1 is
within a range of .+-.2.degree. of 120.degree. as described with
reference to General Formula (G1), molecular structure distortion
of the pyridine ring or the pyrimidine ring can be inhibited. When
the bond angle denoted by .alpha. is greater than or equal to
120.degree. and less than 129.degree. as described with reference
to General Formulae (G5) to (G7), molecular structure distortion of
the pyridine ring or the pyrimidine ring can be inhibited.
[0092] In this manner, in the organometallic iridium complexes of
embodiments of the present invention represented by General
Formulae (G1) to (G7), the dihedral angle or bond angle between the
pyridine or pyrimidine ring and the phenyl group bonded to the
pyridine or pyrimidine ring is in the predetermined range, so that
molecular structure distortion of the pyridine ring or the
pyrimidine ring can be inhibited, or extension of .pi.-conjugation
between the pyridine or pyrimidine ring and the phenyl group can be
inhibited by a twist formed because of steric hindrance. Thus, an
emission spectrum of each of the organometallic iridium complexes
can be shifted to a shorter wavelength side. In addition, higher
efficiency can be achieved.
[0093] In each of the organometallic iridium complexes of
embodiments of the present invention represented by General
Formulae (G1) to (G7), the metal iridium and the ligand form a
metal-carbon bond, so that electric charges are easily transferred
from the metal to the pyridine or pyrimidine ring of the ligand
(metal to ligand charge transfer (MLCT) transition easily occurs).
As a result, phosphorescence, which is a forbidden transition,
easily occurs, the triplet excitation lifetime is shortened, and
the emission efficiency of the organometallic iridium complex can
be increased.
[0094] Note that in General Formula (G2), (G3), (G5) or (G6), the
monoanionic ligand can be represented by any of General Formulae
(L1) to (L7). It is particularly preferable that the monoanionic
ligand have the structure represented by General Formula (L1),
i.e., a structure including a beta-diketone. It is further
preferable that the monoanionic ligand have a structure including
acetylacetone as illustrated in General Formulae (G4) and (G7).
When the monoanionic ligand has a structure including a
beta-diketone or a structure including acetylacetone, the emission
wavelength can be reduced.
##STR00022## ##STR00023##
[0095] In General Formulae (L1) to (L7), R.sup.71 to R.sup.109
independently represent any one of hydrogen, a substituted or
unsubstituted alkyl group having 1 to 6 carbon atoms, a halogen, a
vinyl group, a substituted or unsubstituted haloalkyl group having
1 to 6 carbon atoms, a substituted or unsubstituted alkoxy group
having 1 to 6 carbon atoms, and a substituted or unsubstituted
alkylthio group having 1 to 6 carbon atoms. In addition, A.sup.1 to
A.sup.3 independently represent any one of nitrogen and carbon
bonded to hydrogen or to a substituent R. The substituent R is any
one of an alkyl group having 1 to 6 carbon atoms, a halogen, a
haloalkyl group having 1 to 6 carbon atoms, and a phenyl group.
[0096] Next, specific structural formulae of the above-described
organometallic iridium complexes of embodiments of the present
invention are shown (Structural Formulae (100) to (134)). However,
one embodiment of the present invention is not limited thereto.
##STR00024## ##STR00025## ##STR00026## ##STR00027## ##STR00028##
##STR00029## ##STR00030## ##STR00031## ##STR00032##
##STR00033##
[0097] Note that organometallic iridium complexes represented by
Structural Formulae (100) to (134) are novel substances capable of
emitting phosphorescence. There can be geometrical isomers and
stereoisomers of these substances depending on the type of the
ligand. The organometallic iridium complex of one embodiment of the
present invention includes all of these isomers.
[0098] Next, an example of a method for synthesizing the
organometallic iridium complex represented by General Formula (G2)
is described.
<<Method for Synthesizing Pyridine Derivative or Pyrimidine
Derivative Represented by General Formula (G0)>>
[0099] First, an example of a method for synthesizing a pyridine
derivative or a pyrimidine derivative represented by General
Formula (G0) is described.
##STR00034##
[0100] In General Formula (G0), R.sup.1 to R.sup.9 independently
represent any one of hydrogen and a substituted or unsubstituted
alkyl group having 1 to 6 carbon atoms. Note that at least one of
R.sup.2 and R.sup.6 represents an alkyl group having 1 to 6 carbon
atoms. X represents any one of a carbon atom and a nitrogen atom,
and the carbon atom has any one of hydrogen and an alkyl group
having 1 to 6 carbon atoms. A dihedral angle between a pyridine
ring and a phenyl group having R.sup.7 to R.sup.9, or a dihedral
angle between a pyrimidine ring and the phenyl group having R.sup.7
to R.sup.9 is greater than or equal to 0.degree. and less than
2.degree.. A dihedral angle between the pyridine ring and a phenyl
group having R.sup.2 to R.sup.6, or a dihedral angle between the
pyrimidine ring and the phenyl group having R.sup.2 to R.sup.6 is
greater than or equal to 30.degree. and less than or equal to
90.degree..
[0101] Synthesis Scheme (A) of the pyridine derivative or
pyrimidine derivative represented by General Formula (G0) is shown
below.
##STR00035##
[0102] In Synthesis Scheme (A), R.sup.1 to R.sup.9 independently
represent any one of hydrogen and a substituted or unsubstituted
alkyl group having 1 to 6 carbon atoms. Note that at least one of
R.sup.2 and R.sup.6 represents an alkyl group having 1 to 6 carbon
atoms. X represents any one of a carbon atom and a nitrogen atom,
and the carbon atom has any one of hydrogen and an alkyl group
having 1 to 6 carbon atoms. A dihedral angle between a pyridine
ring and a phenyl group having R.sup.7 to R.sup.9, or a dihedral
angle between a pyrimidine ring and the phenyl group having R.sup.7
to R.sup.9 is greater than or equal to 0.degree. and less than
2.degree.. A dihedral angle between the pyridine ring and a phenyl
group having R.sup.2 to R.sup.6, or a dihedral angle between the
pyrimidine ring and the phenyl group having R.sup.2 to R.sup.6 is
greater than or equal to 30.degree. and less than or equal to
90.degree.. In addition, Y represents a halogen. As illustrated in
Synthesis Scheme (A), the pyridine derivative or pyrimidine
derivative represented by General Formula (G0) can be synthesized
by causing coupling reaction between 4-halogeno-2-phenylpyridine or
6-halogeno-4-phenylpyrimidine and arylboronic acid.
[0103] Since 4-halogeno-2-phenylpyridine,
6-halogeno-4-phenylpyrimidine, and arylboronic acid described above
are commercially available or can be synthesized, many kinds of
pyridine derivatives and pyrimidine derivatives represented by
General Formula (G0) can be synthesized. Thus, a feature of the
organometallic iridium complex of one embodiment of the present
invention is the abundance of ligand variations.
<<Method for Synthesizing an Organometallic Iridium Complex
of One Embodiment of the Present Invention Represented by General
Formula (G2)>>
[0104] Next, a method for synthesizing the organometallic iridium
complex of one embodiment of the present invention represented by
General Formula (G2), which is formed using the pyridine derivative
or pyrimidine derivative represented by General Formula (G0), is
described.
##STR00036##
[0105] In General Formula (G2), R.sup.1 to R.sup.9 independently
represent any one of hydrogen and a substituted or unsubstituted
alkyl group having 1 to 6 carbon atoms. Note that at least one of
R.sup.2 and R.sup.6 represents an alkyl group having 1 to 6 carbon
atoms. X represents any one of a carbon atom and a nitrogen atom,
and the carbon atom has any one of hydrogen and an alkyl group
having 1 to 6 carbon atoms. Further, L represents a monoanionic
ligand. A dihedral angle between a pyridine ring and a phenyl group
having R.sup.7 to R.sup.9, or a dihedral angle between a pyrimidine
ring and the phenyl group having R.sup.7 to R.sup.9 is greater than
or equal to 0.degree. and less than 2.degree.. A dihedral angle
between the pyridine ring and a phenyl group having R.sup.2 to
R.sup.6, or a dihedral angle between the pyrimidine ring and the
phenyl group having R.sup.2 to R.sup.6 is greater than or equal to
30.degree. and less than or equal to 90.degree..
[0106] Synthesis Scheme (B) of the organometallic iridium complex
represented by General Formula (G2) is shown below.
##STR00037##
[0107] In Synthesis Scheme (B), R.sup.1 to R.sup.9 independently
represent any one of hydrogen and a substituted or unsubstituted
alkyl group having 1 to 6 carbon atoms. Note that at least one of
R.sup.2 and R.sup.6 represents an alkyl group having 1 to 6 carbon
atoms. X represents any one of a carbon atom and a nitrogen atom,
and the carbon atom has any one of hydrogen and an alkyl group
having 1 to 6 carbon atoms. A dihedral angle between a pyridine
ring and a phenyl group having R.sup.7 to R.sup.9, or a dihedral
angle between a pyrimidine ring and the phenyl group having R.sup.7
to R.sup.9 is greater than or equal to 0.degree. and less than
2.degree.. A dihedral angle between the pyridine ring and a phenyl
group having R.sup.2 to R.sup.6, or a dihedral angle between the
pyrimidine ring and the phenyl group having R.sup.2 to R.sup.6 is
greater than or equal to 30.degree. and less than or equal to
90.degree.. In addition, Y represents a halogen.
[0108] As shown in Synthesis Scheme (B), the pyridine derivative or
pyrimidine derivative represented by General Formula (G0) and an
iridium compound which contains a halogen (e.g., iridium chloride,
iridium bromide, or iridium iodide) are heated in an inert gas
atmosphere by using no solvent, an alcohol-based solvent (e.g.,
glycerol, ethylene glycol, 2-methoxyethanol, or 2-ethoxyethanol)
alone, or a mixed solvent of water and one or more of the
alcohol-based solvents, whereby a dinuclear complex (P), which is
one type of an organometallic iridium complex including a
halogen-bridged structure, can be obtained.
[0109] There is no particular limitation on a heating unit, and an
oil bath, a sand bath, or an aluminum block may be used.
Alternatively, microwaves can be used as a heating unit.
[0110] As shown in Synthesis Scheme (C), the dinuclear complex (P)
obtained under Synthesis Scheme (B) is reacted with a ligand H-L in
an inert gas atmosphere, whereby a proton of the ligand H-L is
released and a monoanionic ligand L coordinates to the central
metal iridium. Thus, the organometallic iridium complex of one
embodiment of the present invention represented by General Formula
(G2) can be obtained.
##STR00038##
[0111] In Synthesis Scheme (C), R.sup.1 to R.sup.9 independently
represent any one of hydrogen and a substituted or unsubstituted
alkyl group having 1 to 6 carbon atoms. Note that at least one of
R.sup.2 and R.sup.6 represents an alkyl group having 1 to 6 carbon
atoms. X represents any one of a carbon atom and a nitrogen atom,
and the carbon atom has any one of hydrogen and an alkyl group
having 1 to 6 carbon atoms. A dihedral angle between a pyridine
ring and a phenyl group having R.sup.7 to R.sup.9, or a dihedral
angle between a pyrimidine ring and the phenyl group having R.sup.7
to R.sup.9 is greater than or equal to 0.degree. and less than
2.degree.. A dihedral angle between the pyridine ring and a phenyl
group having R.sup.2 to R.sup.6, or a dihedral angle between the
pyrimidine ring and the phenyl group having R.sup.2 to R.sup.6 is
greater than or equal to 30.degree. and less than or equal to
90.degree.. In addition, Y represents a halogen.
[0112] There is no particular limitation on a heating unit, and an
oil bath, a sand bath, or an aluminum block may be used.
Alternatively, microwaves can be used as a heating unit.
[0113] The above is the description of the example of a method for
synthesizing an organometallic iridium complex of one embodiment of
the present invention; however, one embodiment of the present
invention is not limited thereto and any other synthesis method may
be employed.
[0114] The above-described organometallic iridium complex of one
embodiment of the present invention can emit phosphorescence and
thus can be used as a light-emitting material or a light-emitting
substance of a light-emitting element.
[0115] With the use of the organometallic iridium complex of one
embodiment of the present invention, a light-emitting element, a
light-emitting device, an electronic device, or a lighting device
with high emission efficiency can be provided. Alternatively, it is
possible to provide a light-emitting element, a light-emitting
device, an electronic device, or a lighting device with low power
consumption.
[0116] Note that the structure described in this embodiment can be
combined as appropriate with any of the structures described in
other embodiments.
Embodiment 2
[0117] In this embodiment, a light-emitting element in which the
organometallic iridium complex described in Embodiment 1 as one
embodiment of the present invention is used for a light-emitting
layer is described with reference to FIG. 3.
[0118] In a light-emitting element described in this embodiment, as
illustrated in FIG. 3, an EL layer 102 including a light-emitting
layer 113 is provided between a pair of electrodes (a first
electrode 101 and a second electrode 103), and the EL layer 102
includes a hole-injection layer 111, a hole-transport layer 112, an
electron-transport layer 114, an electron-injection layer 115, a
charge generation layer 116, and the like in addition to the
light-emitting layer 113. Note that in this embodiment, the first
electrode 101 is used as an anode and the second electrode 103 is
used as a cathode.
[0119] By application of a voltage to such a light-emitting
element, holes injected from the first electrode 101 side and
electrons injected from the second electrode 103 side recombine in
the light-emitting layer 113 to raise the organometallic iridium
complex to an excited state. Then, light is emitted when the
organometallic iridium complex in the excited state returns to the
ground state. Thus, the organometallic iridium complex of one
embodiment of the present invention functions as a light-emitting
substance in the light-emitting element.
[0120] The hole-injection layer 111 included in the EL layer 102 is
a layer containing a substance having a high hole-transport
property and an acceptor substance. When electrons are extracted
from the substance having a high hole-transport property with the
acceptor substance, holes are generated. Thus, holes are injected
from the hole-injection layer 111 into the light-emitting layer 113
through the hole-transport layer 112.
[0121] The charge generation layer 116 is a layer containing a
substance having a high hole-transport property and an acceptor
substance. With the acceptor substance, electrons are extracted
from the substance having a high hole-transport property and the
extracted electrons are injected from the electron-injection layer
115 having an electron-injection property into the light-emitting
layer 113 through the electron-transport layer 114. Note that the
charge generation layer 116 is not necessarily provided and a
structure without the charge generation layer 116 may be
employed.
[0122] A specific example in which the light-emitting element
described in this embodiment is manufactured is described.
[0123] For the first electrode 101 and the second electrode 103, a
metal, an alloy, an electrically conductive compound, a mixture
thereof, and the like can be used. Specifically, indium oxide-tin
oxide (ITO: indium tin oxide), indium oxide-tin oxide containing
silicon or silicon oxide, indium oxide-zinc oxide (indium zinc
oxide), indium oxide containing tungsten oxide and zinc oxide, gold
(Au), platinum (Pt), nickel (Ni), tungsten (W), chromium (Cr),
molybdenum (Mo), iron (Fe), cobalt (Co), copper (Cu), palladium
(Pd), and titanium (Ti) can be used. In addition, an element
belonging to Group 1 or Group 2 of the periodic table, for example,
an alkali metal such as lithium (Li) or cesium (Cs), an alkaline
earth metal such as calcium (Ca) or strontium (Sr), magnesium (Mg),
an alloy containing such an element (MgAg, AlLi), a rare earth
metal such as europium (Eu) or ytterbium (Yb), an alloy containing
such an element, graphene, and the like can be used. The first
electrode 101 and the second electrode 103 can be formed by, for
example, a sputtering method, an evaporation method (including a
vacuum evaporation method), or the like.
[0124] As the substance with a high hole-transport property which
is used for the hole-injection layer 111, the hole-transport layer
112, and the charge generation layer 116, the following can be
given, for example: aromatic amine compounds such as
4,4'-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (abbreviation: NPB
or .alpha.-NPD),
N,N'-bis(3-methylphenyl)-N,N'-diphenyl-[1,1'-biphenyl]-4,4'-diamine
(abbreviation: TPD), 4,4',4''-tris(carbazol-9-yl)triphenylamine
(abbreviation: TCTA),
4,4',4''-tris(N,N-diphenylamino)triphenylamine (abbreviation:
TDATA),
4,4',4''-tris[N-(3-methylphenyl)-N-phenylamino]triphenylamine
(abbreviation: MTDATA), and
4,4'-bis[N-(spiro-9,9'-bifluoren-2-yl)-N-phenylamino]biphenyl
(abbreviation: BSPB);
3-[N-(9-phenylcarbazol-3-yl)-N-phenylamino]-9-phenylcarbazole
(abbreviation: PCzPCA1);
3,6-bis[N-(9-phenylcarbazol-3-yl)-N-phenylamino]-9-phenylcarbazole
(abbreviation: PCzPCA2); and
3-[N-(1-naphthyl)-N-(9-phenylcarbazol-3-yl)amino]-9-phenylcarbazole
(abbreviation: PCzPCN1). In addition, carbazole derivatives such as
4,4'-di(N-carbazolyl)biphenyl (abbreviation: CBP),
1,3,5-tris[4-(N-carbazolyl)phenyl]benzene (abbreviation: TCPB), and
9-[4-(10-phenyl-9-anthracenyfiphenyl]-9H-carbazole (abbreviation:
CzPA) can be used. The substances mentioned here are mainly ones
that have a hole mobility of 10.sup.-6 cm.sup.2/Vs or higher. Note
that any substance other than the above substances may be used as
long as the hole-transport property is higher than the
electron-transport property.
[0125] Further, a high molecular compound such as
poly(N-vinylcarbazole) (abbreviation: PVK),
poly(4-vinyltriphenylamine) (abbreviation: PVTPA),
poly[N-(4-{N'-[4-(4-diphenylamino)phenyl]phenyl-N'-phenylamino}phenyl)met-
hacrylamide] (abbreviation: PTPDMA), and
poly[N,N'-bis(4-butylphenyl)-N,N'-bis(phenyl)benzidine]
(abbreviation: Poly-TPD) can be used.
[0126] As examples of the acceptor substance that is used for the
hole-injection layer 111 and the charge generation layer 116, a
transition metal oxide or an oxide of a metal belonging to any of
Group 4 to Group 8 of the periodic table can be given.
Specifically, molybdenum oxide is particularly preferable.
[0127] The light-emitting layer 113 contains, as a guest material,
the organometallic iridium complex of one embodiment of the present
invention serving as a light-emitting substance. The light-emitting
layer 113 also contains, as a host material, a substance having
higher triplet excitation energy than the organometallic iridium
complex.
[0128] Preferable examples of the substance (i.e., host material)
used for dispersing any of the above-described organometallic
iridium complexes include any of compounds having an arylamine
skeleton, such as 2,3-bis(4-diphenylaminophenyl)quinoxaline
(abbreviation: TPAQn) and NPB, carbazole derivatives such as CBP
and 4,4',4''-tris(carbazol-9-yl)triphenylamine (abbreviation:
TCTA), and metal complexes such as
bis[2-(2-hydroxyphenyl)pyridinato]zinc (abbreviation: Znpp.sub.2),
bis[2-(2-hydroxyphenyl)benzoxazolato]zinc (abbreviation:
Zn(BOX).sub.2),
bis(2-methyl-8-quinolinolato)(4-phenylphenolato)aluminum
(abbreviation: BAlq), and tris(8-quinolinolato)aluminum
(abbreviation: Alq.sub.3). Alternatively, a high molecular compound
such as PVK can be used.
[0129] Note that in the case where the light-emitting layer 113
contains the above-described organometallic iridium complex (guest
material) and the host material, phosphorescence with high emission
efficiency can be obtained from the light-emitting layer 113.
[0130] The electron-transport layer 114 is a layer containing a
substance having a high electron-transport property. For the
electron-transport layer 114, a metal complex such as Alq.sub.3,
tris(4-methyl-8-quinolinolato)aluminum (abbreviation: Almq.sub.3),
bis(10-hydroxybenzo[h]quinolinato)beryllium (abbreviation:
BeBq.sub.2), BAlq, Zn(BOX).sub.2, and
bis[2-(2-hydroxyphenyl)benzothiazolato]zinc (abbreviation:
Zn(BTZ).sub.2) can be used. Alternatively, a heteroaromatic
compound such as
2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole
(abbreviation: PBD),
1,3-bis[5-(p-tert-butylphenyl)-1,3,4-oxadiazol-2-yl]benzene
(abbreviation: OXD-7),
3-(4-biphenylyl)-4-phenyl-5-(4-tert-butylphenyl)-1,2,4-triazole
(abbreviation: TAZ),
3-(4-tert-butylphenyl)-4-(4-ethylphenyl)-5-(4-biphenylyl)-1,2,4-triazole
(abbreviation: p-EtTAZ), bathophenanthroline (abbreviation: Bphen),
bathocuproine (abbreviation: BCP), or
4,4'-bis(5-methylbenzoxazol-2-yl)stilbene (abbreviation: BzOs) can
be used. Further alternatively, a high molecular compound such as
poly(2,5-pyridinediyl) (abbreviation: PPy),
poly[(9,9-dihexylfluorene-2,7-diyl)-co-(pyridine-3,5-diyl)]
(abbreviation: PF-Py), and
poly[(9,9-dioctylfluorene-2,7-diyl)-co-(2,2'-bipyridine-6,6'-diyl)]
(abbreviation: PF-BPy) can be used. The substances mentioned here
are mainly ones that have an electron mobility of 10.sup.-6
cm.sup.2/Vs or higher. Note that any substance other than the above
substances may be used for the electron-transport layer 114 as long
as the electron-transport property is higher than the
hole-transport property.
[0131] Further, the electron-transport layer 114 is not limited to
a single layer, and a stacked layer in which two or more layers
containing any of the above-described substances are stacked may be
used.
[0132] The electron-injection layer 115 is a layer containing a
substance having a high electron-injection property. For the
electron-injection layer 115, an alkali metal compound or an
alkaline earth metal compound, such as lithium fluoride (LiF),
cesium fluoride (CsF), calcium fluoride (CaF.sub.2), and lithium
oxide (LiO.sub.x) can be used. Alternatively, a rare earth metal
compound such as erbium fluoride (ErF.sub.3) can be used. Electride
may also be used for the electron-injection layer 115. Examples of
the electride include a mixed oxide of calcium and aluminum that
contains electrons at a high concentration. The substances for
forming the electron-transport layer 114, which are described
above, may be used.
[0133] Alternatively, a composite material in which an organic
compound and an electron donor (donor) are mixed may be used for
the electron-injection layer 115. Such a composite material is
excellent in an electron-injection property and an
electron-transport property because electrons are generated in the
organic compound by the electron donor. In this case, the organic
compound is preferably a material excellent in transporting the
generated electrons. Specifically, the substances for forming the
electron-transport layer 114 (e.g., a metal complex and a
heteroaromatic compound), which are described above, or the like
can be used. As the electron donor, a substance showing an
electron-donating property with respect to the organic compound may
be used. Preferable examples are an alkali metal, an alkaline earth
metal, and a rare earth metal. Specifically, lithium, cesium,
magnesium, calcium, erbium, ytterbium and the like can be used. In
addition, alkali metal oxide and alkaline earth metal oxide such as
lithium oxide, calcium oxide, and barium oxide can be given. A
Lewis base such as magnesium oxide can alternatively be used. An
organic compound such as tetrathiafulvalene (abbreviation: TTF) can
alternatively be used.
[0134] Note that each of the above-described hole-injection layer
111, hole-transport layer 112, light-emitting layer 113,
electron-transport layer 114, electron-injection layer 115, and
charge generation layer 116 can be formed by an evaporation method
(e.g., a vacuum evaporation method), an ink-jet method, a coating
method, or the like.
[0135] In the above-described light-emitting element, current flows
owing to a potential difference generated between the first
electrode 101 and the second electrode 103 and holes and electrons
recombine in the EL layer 102, whereby light is emitted. Then, the
emitted light is extracted outside through one or both of the first
electrode 101 and the second electrode 103. Therefore, one or both
of the first electrode 101 and the second electrode 103 are
electrodes having a light-transmitting property.
[0136] The above-described light-emitting element can emit
phosphorescence originating from the organometallic iridium complex
and thus can have higher efficiency than a light-emitting element
using a fluorescent compound.
[0137] Note that the structure described in this embodiment can be
combined as appropriate with any of the structures described in
other embodiments.
Embodiment 3
[0138] In this embodiment, a light-emitting element in which two or
more kinds of organic compounds as well as the organometallic
iridium complex of one embodiment of the present invention are used
for a light-emitting layer is described.
[0139] A light-emitting element described in this embodiment
includes an EL layer 203 between a pair of electrodes (a first
electrode 201 and a second electrode 202) as illustrated in FIG. 4.
Note that the EL layer 203 includes at least a light-emitting layer
204 and may include a hole-injection layer, a hole-transport layer,
an electron-transport layer, an electron-injection layer, a charge
generation layer, and the like. Note that for the hole-injection
layer, the hole-transport layer, the electron-transport layer, the
electron-injection layer, and the charge generation layer, the
substances described in Embodiment 2 can be used. FIG. 4
illustrates an example in which a first layer 210 is provided
between the first electrode 201 and the light-emitting layer 204
and a second layer 212 is provided between the second electrode 202
and the light-emitting layer 204. As the first layer 210 and the
second layer 212, optimal layers can be selected by the
practitioner from the above-described hole-injection layer,
hole-transport layer, electron-transport layer, electron-injection
layer, charge generation layer, and the like. Note that in this
embodiment, the first electrode 201 is used as an anode and the
second electrode 202 is used as a cathode.
[0140] The light-emitting layer 204 described in this embodiment
contains a phosphorescent compound 205 using the organometallic
iridium complex of one embodiment of the present invention, a first
organic compound 206, and a second organic compound 207. Note that
the phosphorescent compound 205 is a guest material in the
light-emitting layer 204. Moreover, one of the first organic
compound 206 and the second organic compound 207, the content of
which is higher than that of the other in the light-emitting layer
204, is a host material in the light-emitting layer 204.
[0141] When the light-emitting layer 204 has the structure in which
the guest material is dispersed in the host material,
crystallization of the light-emitting layer can be suppressed.
Further, it is possible to suppress concentration quenching due to
high concentration of the guest material, and thus the
light-emitting element can have higher emission efficiency.
[0142] Note that it is preferable that a triplet excitation energy
level (T.sub.1 level) of each of the first organic compound 206 and
the second organic compound 207 be higher than that of the
phosphorescent compound 205. The reason for this is that, when the
T.sub.1 level of the first organic compound 206 or the second
organic compound 207 is lower than that of the phosphorescent
compound 205, the triplet excitation energy of the phosphorescent
compound 205, which is to contribute to light emission, is quenched
by the first organic compound 206 or the second organic compound
207 and accordingly the emission efficiency decreases.
[0143] Here, for improvement in efficiency of energy transfer from
a host material to a guest material, Forster mechanism
(dipole-dipole interaction) and Dexter mechanism (electron exchange
interaction), which are known as mechanisms of energy transfer
between molecules, are considered. According to the mechanisms, it
is preferable that an emission spectrum of a host material (a
fluorescence spectrum in energy transfer from a singlet excited
state, and a phosphorescence spectrum in energy transfer from a
triplet excited state) have a large overlap with an absorption
spectrum of a guest material (specifically, a spectrum in an
absorption band on the longest wavelength (lowest energy) side).
However, in general, it is difficult to obtain an overlap between a
fluorescence spectrum of a host material and an absorption spectrum
in an absorption band in the longest wavelength (lowest energy)
range of a guest material. The reason for this is as follows: if
the fluorescence spectrum of the host material overlaps with the
absorption spectrum in the absorption band on the longest
wavelength (lowest energy) side of the guest material, since the
phosphorescence spectrum of the host material is located on a
longer wavelength (lower energy) side than the fluorescence
spectrum, the T.sub.1 level of the host material becomes lower than
the T.sub.1 level of the phosphorescent compound and the
above-described problem of quenching occurs; yet, when the host
material is designed in such a manner that the T.sub.1 level of the
host material is higher than the T.sub.1 level of the
phosphorescent compound in order to avoid the problem of quenching,
the fluorescence spectrum of the host material is shifted to the
shorter wavelength (higher energy) side, and thus the fluorescence
spectrum does not have any overlap with the absorption spectrum in
the absorption band on the longest wavelength (lowest energy) side
of the guest material. For that reason, in general, it is difficult
to obtain an overlap between a fluorescence spectrum of a host
material and an absorption spectrum in an absorption band in the
longest wavelength (lowest energy) range of a guest material so as
to maximize energy transfer from a singlet excited state of the
host material.
[0144] Thus, in this embodiment, the first organic compound 206
preferably forms an excited complex (also referred to as exciplex)
in combination with the second organic compound 207. In that case,
the first organic compound 206 and the second organic compound 207
form an exciplex at the time of recombination of carriers
(electrons and holes) in the light-emitting layer 204. Thus, in the
light-emitting layer 204, a fluorescence spectrum of the first
organic compound 206 and that of the second organic compound 207
are converted into an emission spectrum of the exciplex which is
located on a longer wavelength side. Moreover, when the first
organic compound 206 and the second organic compound 207 are
selected in such a manner that the emission spectrum of the
exciplex has a large overlap with the absorption spectrum of the
guest material, energy transfer from a singlet excited state can be
maximized. Note that also in the case of a triplet excited state,
energy transfer from the exciplex, not the host material, is
presumed to occur.
[0145] For the phosphorescent compound 205, the organometallic
iridium complex of one embodiment of the present invention is used.
Although the combination of the first organic compound 206 and the
second organic compound 207 can be determined such that an exciplex
is formed, a combination of a compound that easily accepts
electrons (a compound having an electron-trapping property) and a
compound that easily accepts holes (a compound having a
hole-trapping property) is preferably employed.
[0146] Examples of the compound that easily accepts electrons
include 2-[3-(dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxaline
(abbreviation: 2mDBTPDBq-II),
2-[4-(3,6-diphenyl-9H-carbazol-9-yl)phenyl]dibenzo[f,h]quinoxaline
(abbreviation: 2CzPDBq-III),
7-[3-(dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxaline
(abbreviation: 7mDBTPDBq-II), and
6-[3-(dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxaline
(abbreviation: 6mDBTPDBq-II).
[0147] Examples of the compound that easily accepts holes include
4-phenyl-4'-(9-phenyl-9H-carbazol-3-yl)triphenylamine
(abbreviation: PCBA1BP),
3-[N-(1-naphthyl)-N-(9-phenylcarbazol-3-yl)amino]-9-phenylcarba-
zole (abbreviation: PCzPCN1),
4,4',4''-tris[N-(1-naphthyl)-N-phenylamino]triphenylamine
(abbreviation: 1'-TNATA),
2,7-bis[N-(4-diphenylaminophenyl)-N-phenylamino]spiro-9,9'-bifluorene
(abbreviation: DPA2SF),
N,N'-bis(9-phenylcarbazol-3-yl)-N,N'-diphenylbenzene-1,3-diamine
(abbreviation: PCA2B),
N-(9,9-dimethyl-2-N,N',N'-diphenylamino-9H-fluoren-7-yl)diphenylamine
(abbreviation: DPNF),
N,N',N''-triphenyl-N,N',N''-tris(9-phenylcarbazol-3-yl)benzene-1,3,5-tria-
mine (abbreviation: PCA3B),
2-[N-(9-phenylcarbazol-3-yl)-N-phenylamino]spiro-9,9'-bifluorene
(abbreviation: PCASF),
2-[N-(4-diphenylaminophenyl)-N-phenylamino]spiro-9,9'-bifluorene
(abbreviation: DPASF),
N,N'-bis[4-(carbazol-9-yl)phenyl]-N,N'-diphenyl-9,9-dimethylfluorene-2,7--
diamine (abbreviation: YGA2F),
4,4'-bis[N-(3-methylphenyl)-N-phenylamino]biphenyl (abbreviation:
TPD), 4,4'-bis[N-(4-diphenylaminophenyl)-N-phenylamino]biphenyl
(abbreviation: DPAB),
N-(9,9-dimethyl-9H-fluoren-2-yl)-N-{9,9-dimethyl-2-[N'-phenyl-N'-(-
9,9-dimethyl-9H-fluoren-2-yl)amino]-9H-fluoren-7-yl}phenylamine
(abbreviation: DFLADFL),
3-[N-(9-phenylcarbazol-3-yl)-N-phenylamino]-9-phenylcarbazole
(abbreviation: PCzPCA1),
3-[N-(4-diphenylaminophenyl)-N-phenylamino]-9-phenylcarbazole
(abbreviation: PCzDPA1),
3,6-bis[N-(4-diphenylaminophenyl)-N-phenylamino]-9-phenylcarbazole
(abbreviation: PCzDPA2),
4,4'-bis(N-{4-[N'-(3-methylphenyl)-N'-phenylamino]phenyl}-N-phenylamino)b-
iphenyl (abbreviation: DNTPD),
3,6-bis[N-(4-diphenylaminophenyl)-N-(1-naphthyl)amino]-9-phenylcarbazole
(abbreviation: PCzTPN2), and
3,6-bis[N-(9-phenylcarbazol-3-yl)-N-phenylamino]-9-phenylcarbazole
(abbreviation: PCzPCA2).
[0148] As for the above-described first and second organic
compounds 206 and 207, the present invention is not limited to the
above examples. The combination is determined so that an exciplex
can be formed, the emission spectrum of the exciplex overlaps with
the absorption spectrum of the phosphorescent compound 205, and the
peak of the emission spectrum of the exciplex has a longer
wavelength than the peak of the absorption spectrum of the
phosphorescent compound 205.
[0149] Note that in the case where a compound that easily accepts
electrons and a compound that easily accepts holes are used for the
first organic compound 206 and the second organic compound 207,
carrier balance can be controlled by the mixture ratio of the
compounds. Specifically, the weight ratio of the first organic
compound to the second organic compound is preferably 1:9 to
9:1.
[0150] In the light-emitting element described in this embodiment,
energy transfer efficiency can be improved owing to energy transfer
utilizing an overlap between an emission spectrum of an exciplex
and an absorption spectrum of a phosphorescent compound; thus, it
is possible to achieve high external quantum efficiency of the
light-emitting element.
[0151] Note that in another structure of one embodiment of the
present invention, the light-emitting layer 204 can be formed using
a host molecule having a hole-trapping property and a host molecule
having an electron-trapping property as the two kinds of organic
compounds (the first organic compound 206 and the second organic
compound 207) other than the phosphorescent compound 205 (guest
material) so that a phenomenon (guest coupled with complementary
hosts: GCCH) occurs in which holes and electrons are introduced to
guest molecules existing in the two kinds of host molecules and the
guest molecules are brought into an excited state.
[0152] At this time, the host molecule having a hole-trapping
property and the host molecule having an electron-trapping property
can be respectively selected from the above-described compounds
that easily accept holes and the above-described compounds that
easily accept electrons.
[0153] Note that the structure described in this embodiment can be
combined as appropriate with any of the structures described in
other embodiments.
Embodiment 4
[0154] In this embodiment, as one embodiment of the present
invention, a light-emitting element (hereinafter referred to as
tandem light-emitting element) in which a charge generation layer
is provided between a plurality of EL layers is described.
[0155] A light-emitting element described in this embodiment is a
tandem light-emitting element including a plurality of EL layers (a
first EL layer 302(1) and a second EL layer 302(2)) between a pair
of electrodes (a first electrode 301 and a second electrode 304) as
illustrated in FIG. 5A.
[0156] In this embodiment, the first electrode 301 functions as an
anode, and the second electrode 304 functions as a cathode. Note
that the first electrode 301 and the second electrode 304 can have
structures similar to those described in Embodiment 2. In addition,
although the plurality of EL layers (the first EL layer 302(1) and
the second EL layer 302(2)) may have a structure similar to that of
the EL layer described in Embodiment 2 or 3, any of the EL layers
may have a structure similar to that of the EL layer described in
Embodiment 2 or 3. In other words, the structures of the first EL
layer 302(1) and the second EL layer 302(2) may be the same or
different from each other and can be similar to that of the EL
layer described in Embodiment 2 or 3.
[0157] Further, a charge generation layer 305 is provided between
the plurality of EL layers (the first EL layer 302(1) and the
second EL layer 302(2)). The charge generation layer 305 has a
function of injecting electrons into one of the EL layers and
injecting holes into the other of the EL layers when a voltage is
applied between the first electrode 301 and the second electrode
304. In this embodiment, when a voltage is applied such that the
potential of the first electrode 301 is higher than that of the
second electrode 304, the charge generation layer 305 injects
electrons into the first EL layer 302(1) and injects holes into the
second EL layer 302(2).
[0158] Note that in terms of light extraction efficiency, the
charge generation layer 305 preferably has a light-transmitting
property with respect to visible light (specifically, the charge
generation layer 305 has a visible light transmittance of 40% or
more). Further, the charge generation layer 305 functions even if
it has lower conductivity than the first electrode 301 or the
second electrode 304.
[0159] The charge generation layer 305 may have either a structure
in which an electron acceptor (acceptor) is added to an organic
compound having a high hole-transport property or a structure in
which an electron donor (donor) is added to an organic compound
having a high electron-transport property. Alternatively, both of
these structures may be stacked.
[0160] In the case of the structure in which an electron acceptor
is added to an organic compound having a high hole-transport
property, as the organic compound having a high hole-transport
property, for example, an aromatic amine compound such as NPB, TPD,
TDATA, MTDATA, or
4,4'-bis[N-(spiro-9,9'-bifluoren-2-yl)-N-phenylamino]biphenyl
(abbreviation: BSPB), or the like can be used. The substances
mentioned here are mainly ones that have a hole mobility of
10.sup.-6 cm.sup.2/Vs or higher. Note that any substance other than
the above substances may be used as long as they are organic
compounds with a hole-transport property higher than an
electron-transport property.
[0161] Further, as the electron acceptor,
7,7,8,8-tetracyano-2,3,5,6-tetrafluoroquinodimethane (abbreviation:
F.sub.4-TCNQ), chloranil, or the like can be used. Alternatively, a
transition metal oxide can be used. Further alternatively, an oxide
of metals that belong to Group 4 to Group 8 of the periodic table
can be used. Specifically, it is preferable to use vanadium oxide,
niobium oxide, tantalum oxide, chromium oxide, molybdenum oxide,
tungsten oxide, manganese oxide, or rhenium oxide because the
electron-accepting property is high. Among these, molybdenum oxide
is especially preferable because it is stable in the air, has a low
hygroscopic property, and is easily handled.
[0162] In the case of the structure in which an electron donor is
added to an organic compound having a high electron-transport
property, as the organic compound having a high electron-transport
property for example, a metal complex having a quinoline skeleton
or a benzoquinoline skeleton, such as Alq, Almq.sub.3, BeBq.sub.2,
or BAlq, or the like can be used. Alternatively, it is possible to
use a metal complex having an oxazole-based ligand or a
thiazole-based ligand, such as Zn(BOX).sub.2 or Zn(BTZ).sub.2.
Further alternatively, instead of a metal complex, it is possible
to use PBD, OXD-7, TAZ, Bphen, BCP, or the like. The substances
mentioned here are mainly ones that have an electron mobility of
10.sup.-6 cm.sup.2/Vs or higher. Note that any substance other than
the above substances may be used as long as they are organic
compounds with an electron-transport property higher than a
hole-transport property.
[0163] As the electron donor, it is possible to use an alkali
metal, an alkaline earth metal, a rare earth metal, a metal
belonging to Group 2 or 13 of the periodic table, or an oxide or a
carbonate thereof. Specifically, it is preferable to use lithium
(Li), cesium (Cs), magnesium (Mg), calcium (Ca), ytterbium (Yb),
indium (In), lithium oxide, cesium carbonate, or the like.
Alternatively, an organic compound such as tetrathianaphthacene may
be used as the electron donor.
[0164] Note that forming the charge generation layer 305 by using
any of the above materials can suppress an increase in drive
voltage caused by the stack of the EL layers.
[0165] Although FIG. 5A shows the light-emitting element having two
EL layers, the present invention can be similarly applied to a
light-emitting element in which n EL layers (302(1) to 302(n)) (n
is three or more) are stacked as illustrated in FIG. 5B. In the
case where a plurality of EL layers are included between a pair of
electrodes as in the light-emitting element according to this
embodiment, by providing charge generation layers (305(1) to
305(n-1)) between the EL layers, light emission in a high luminance
region can be obtained with current density kept low. Since the
current density can be kept low, the element can have a long
lifetime. When the light-emitting element is applied to lighting,
voltage drop due to resistance of an electrode material can be
reduced, which results in homogeneous light emission in a large
area. Moreover, a light-emitting device having low power
consumption, which can be driven at low voltage, can be
obtained.
[0166] By making the EL layers emit light of different colors from
each other, the light-emitting element can provide light emission
of a desired color as a whole. For example, by forming a
light-emitting element having two EL layers such that the emission
color of the first EL layer and the emission color of the second EL
layer are complementary colors, the light-emitting element can
provide white light emission as a whole. Note that the word
"complementary" means color relationship in which an achromatic
color is obtained when colors are mixed. In other words, when light
obtained from a light-emitting substance and light of a
complementary color are mixed, white light emission can be
obtained.
[0167] Further, the same can be applied to a light-emitting element
having three EL layers. For example, the light-emitting element as
a whole can provide white light emission when the emission color of
the first EL layer is red, the emission color of the second EL
layer is green, and the emission color of the third EL layer is
blue.
[0168] Note that the structure described in this embodiment can be
combined as appropriate with any of the structures described in
other embodiments.
Embodiment 5
[0169] In this embodiment, a light-emitting device that includes a
light-emitting element using the organometallic iridium complex of
one embodiment of the present invention is described.
[0170] The light-emitting device can be either a passive matrix
light-emitting device or an active matrix light-emitting device.
Note that any of the light-emitting elements described in other
embodiments can be applied to the light-emitting device described
in this embodiment.
[0171] In this embodiment, an active matrix light-emitting device
is described with reference to FIGS. 6A and 6B.
[0172] Note that FIG. 6A is a top view illustrating a
light-emitting device and FIG. 6B is a cross-sectional view taken
along the dashed-dotted line A-B in FIG. 6A. The active matrix
light-emitting device according to this embodiment includes a pixel
portion 402 provided over an element substrate 401, a driver
circuit portion 403 having a function of a source line driver
circuit, and driver circuit portions 404a and 404b each having a
function of a gate line driver circuit. The pixel portion 402, the
driver circuit portion 403, and the driver circuit portions 404a
and 404b are sealed between the element substrate 401 and the
sealing substrate 406 with a sealant 405.
[0173] In addition, a lead wiring 407 (not shown in FIG. 6A) is
provided over the element substrate 401. The lead wiring 407 is
provided for connecting an external input terminal through which a
signal (e.g., a video signal, a clock signal, a start signal, and a
reset signal) or a potential from the outside is transmitted to the
driver circuit portion 403 and the driver circuit portions 404a and
404b. Here is shown an example in which an FPC 408 is provided as
the external input terminal. Note that the FPC 408 has a function
of what is called a flexible printed circuit. Although the FPC 408
is illustrated alone, this FPC 408 may be provided with a printed
wiring board (PWB).
[0174] Next, the light-emitting device illustrated in FIG. 6A will
be described with reference to FIG. 6B. Note that FIG. 6B does not
illustrate cross-sectional structures of the driver circuit
portions 404a and 404b. The structures of the driver circuit
portions 404a and 404b may be the same as or different from that of
the driver circuit portion 403.
[0175] FIG. 6B illustrates an example of the driver circuit portion
403 in which an FET 409 and an FET 410 are combined. The FET 409
and the FET 410 included in the driver circuit portion 403 may be
formed with a circuit including transistors having the same
conductivity type (either an n-channel transistor or a p-channel
transistor) or a CMOS circuit including an n-channel transistor and
a p-channel transistor. Furthermore, in the driver circuit portion
403, one transistor may be used or three or more transistors may be
combined. Although this embodiment shows a driver integrated type
in which the driver circuit is formed over the substrate, the
driver circuit is not necessarily formed over the substrate, and
may be formed outside the substrate.
[0176] The pixel portion 402 is formed of a plurality of pixels
each of which includes a switching FET 411, a current control FET
412, and a first electrode 413 which is electrically connected to a
wiring (a source electrode or a drain electrode) of the current
control FET 412. Although the pixel portion 402 includes two FETs,
the switching FET 411 and the current control FET 412, in this
embodiment, one embodiment of the present invention is not limited
thereto. The pixel portion 402 may include, for example, three or
more FETs and a capacitor in combination.
[0177] As the FETs 409, 410, 411, and 412, for example, a staggered
transistor, an inverted staggered transistor, or a fin-type
transistor can be used. Examples of a semiconductor material that
can be used for the FETs 409, 410, 411, and 412 include Group IV
semiconductors (e.g., silicon and gallium), compound
semiconductors, oxide semiconductors, and organic semiconductors.
In addition, there is no particular limitation on the crystallinity
of the semiconductor material, and an amorphous semiconductor or a
crystalline semiconductor can be used. It is particularly
preferable to use an oxide semiconductor for the FETs 409, 410,
411, and 412. Examples of the oxide semiconductor include an In--Ga
oxide and an In-M-Zn oxide (M is Al, Ga, Y, Zr, La, Ce, or Nd). For
example, an oxide semiconductor that has an energy gap of 2 eV or
more, preferably 2.5 eV or more, further preferably 3 eV or more is
used for the FETs 409, 410, 411, and 412, so that the off-state
current of the transistors can be reduced.
[0178] An insulator 414 is formed to cover end portions of the
first electrode 413. In this embodiment, the insulator 414 is
formed using a positive photosensitive acrylic resin. The first
electrode 413 is used as an anode in this embodiment.
[0179] The insulator 414 preferably has a curved surface with
curvature at an upper end portion or a lower end portion thereof.
This enables the coverage with a film to be formed over the
insulator 414 to be favorable. The insulator 414 can be formed
using, for example, either a negative photosensitive resin or a
positive photosensitive resin. The material of the insulator 414 is
not limited to an organic compound, and an inorganic compound such
as silicon oxide, silicon oxynitride, or silicon nitride can also
be used.
[0180] An EL layer 415 and a second electrode 416 are formed over
the first electrode 413. In the EL layer 415, at least a
light-emitting layer is provided. Further, in the EL layer 415, a
hole-injection layer, a hole-transport layer, an electron-transport
layer, an electron-injection layer, a charge generation layer, and
the like can be provided as appropriate in addition to the
light-emitting layer. Note that in this embodiment, the second
electrode 416 is used as a cathode.
[0181] A light-emitting element 417 includes the first electrode
413, the EL layer 415, and the second electrode 416. For the first
electrode 413, the EL layer 415, and the second electrode 416, the
materials described in Embodiment 2 can be used. Although not
illustrated, the second electrode 416 is electrically connected to
the FPC 408 which is an external input terminal.
[0182] Although the cross-sectional view of FIG. 6B illustrates
only one light-emitting element 417, a plurality of light-emitting
elements are arranged in matrix in the pixel portion 402.
Light-emitting elements which provide three kinds of light emission
(R, G, and B) are selectively formed in the pixel portion 402,
whereby a light-emitting device capable of full color display can
be fabricated. Other than a light-emitting element which provides
three kinds of light emission (R, G, and B), for example, a
light-emitting element which emits white (W), yellow (Y), magenta
(M), and cyan (C) light may be formed. When the above
light-emitting element that provides several kinds of light
emission is provided as well as a light-emitting element that
provides three kinds of light emission (R, G, and B), for example,
higher color purity, lower power consumption, or the like can be
achieved. Alternatively, a light-emitting device capable of
performing full color display may be provided by combining
light-emitting elements capable of emitting white light with color
filters.
[0183] Further, the sealing substrate 406 is attached to the
element substrate 401 with the sealant 405, whereby the
light-emitting element 417 is provided in a space 418 surrounded by
the element substrate 401, the sealing substrate 406, and the
sealant 405. The space 418 may be filled with an inert gas (such as
nitrogen or argon), or the sealant 405.
[0184] An epoxy-based resin is preferably used for the sealant 405.
It is preferable that such a material do not transmit moisture or
oxygen as much as possible. As the sealing substrate 406, a glass
substrate, a quartz substrate, or a plastic substrate formed of
fiber reinforced plastic (FRP), poly(vinyl fluoride) (PVF), a
polyester-based resin, an acrylic-based resin, or the like can be
used.
[0185] As described above, an active matrix light-emitting device
can be obtained.
[0186] Note that the structure described in this embodiment can be
combined as appropriate with any of the structures described in
other embodiments.
Embodiment 6
[0187] This embodiment describes examples in which a light-emitting
element including the organometallic iridium complex of one
embodiment of the present invention or a light-emitting device
using the light-emitting element is applied to a variety of
electronic devices with reference to FIGS. 7A to 7D.
[0188] Examples of the electronic devices are a television device
(also referred to as television or television receiver), a monitor
of a computer or the like, a camera such as a digital camera or a
digital video camera, a digital photo frame, a mobile phone (also
referred to as cellular phone or cellular phone device), a portable
game machine, a portable information terminal, an audio reproducing
device, and a large-sized game machine such as a pachinko
machine.
[0189] An electronic device or a lighting device that has a
light-emitting portion with a curved surface can be obtained with
the use of the light-emitting element of one embodiment of the
present invention which is manufactured over a substrate having
flexibility.
[0190] In addition, an electronic device or a lighting device that
has a see-through light-emitting portion can be obtained with the
use of the light-emitting element of one embodiment of the present
invention in which a pair of electrodes are formed using a material
having a property of transmitting visible light.
[0191] Further, a light-emitting device to which one embodiment of
the present invention is applied can also be applied to lighting
for motor vehicles, examples of which are lighting for a dashboard,
a windshield, a ceiling, and the like.
[0192] FIG. 7A illustrates an example of a television set. In a
television set 7100, a display portion 7103 is incorporated in a
housing 7101. Images can be displayed on the display portion 7103,
and the light-emitting device can be used for the display portion
7103. In addition, here, the housing 7101 is supported by a stand
7105.
[0193] Operation of the television set 7100 can be performed with
an operation switch of the housing 7101 or a separate remote
controller 7110. With operation keys 7109 of the remote controller
7110, channels and volume can be controlled and images displayed on
the display portion 7103 can be controlled. Furthermore, the remote
controller 7110 may be provided with a display portion 7107 for
displaying data output from the remote controller 7110.
[0194] Note that the television set 7100 is provided with a
receiver, a modem, and the like. With the receiver, a general
television broadcast can be received. Furthermore, when the
television set 7100 is connected to a communication network by
wired or wireless connection via the modem, one-way (from a
transmitter to a receiver) or two-way (between a transmitter and a
receiver, between receivers, or the like) data communication can be
performed.
[0195] FIG. 7B illustrates a computer having a main body 7201, a
housing 7202, a display portion 7203, a keyboard 7204, an external
connection port 7205, a pointing device 7206, and the like. Note
that this computer is manufactured using the light-emitting device
for the display portion 7203.
[0196] FIG. 7C illustrates a smart watch. The smart watch includes
a housing 7302, a display panel 7304, operation buttons 7311 and
7312, a connection terminal 7313, a band 7321, a clasp 7322, and
the like.
[0197] The display panel 7304 mounted in the housing 7302 serving
as a bezel includes a non-rectangular display region. The display
panel 7304 may have a rectangular display region. The display panel
7304 can display an icon 7305 indicating time, another icon 7306,
and the like.
[0198] The smart watch in FIG. 7C can have a variety of functions,
for example, a function of displaying a variety of information
(e.g., a still image, a moving image, and a text image) on a
display portion, a touch panel function, a function of displaying a
calendar, date, time, and the like, a function of controlling
processing with a variety of software (programs), a wireless
communication function, a function of being connected to a variety
of computer networks with a wireless communication function, a
function of transmitting and receiving a variety of data with a
wireless communication function, and a function of reading program
or data stored in a recording medium and displaying the program or
data on a display portion.
[0199] The housing 7302 can include a speaker, a sensor (a sensor
having a function of measuring force, displacement, position,
speed, acceleration, angular velocity, rotational frequency,
distance, light, liquid, magnetism, temperature, chemical
substance, sound, time, hardness, electric field, current, voltage,
electric power, radiation, flow rate, humidity, gradient,
oscillation, odor, or infrared rays), a microphone, and the like.
Note that the smart watch can be manufactured using the
light-emitting device for the display panel 7304.
[0200] FIG. 7D illustrates an example of a mobile phone. A mobile
phone 7400 includes a housing 7401 provided with a display portion
7402, a microphone 7406, a speaker 7405, a camera 7407, an external
connection portion 7404, an operation button 7403, and the like. In
the case where the light-emitting element of one embodiment of the
present invention is formed over a flexible substrate, the
light-emitting element can be used for the display portion 7402
having a curved surface as illustrated in FIG. 7D.
[0201] When the display portion 7402 of the mobile phone 7400
illustrated in FIG. 7D is touched with a finger or the like, data
can be input to the mobile phone 7400. Further, operations such as
making a call and composing e-mail can be performed by touching the
display portion 7402 with a finger or the like.
[0202] There are mainly three screen modes of the display portion
7402. The first mode is a display mode mainly for displaying
images. The second mode is an input mode mainly for inputting data
such as text. The third mode is a display-and-input mode in which
two modes of the display mode and the input mode are combined.
[0203] For example, in the case of making a call or composing
e-mail, a text input mode mainly for inputting text is selected for
the display portion 7402 so that text displayed on the screen can
be input. In this case, it is preferable to display a keyboard or
number buttons on almost the entire screen of the display portion
7402.
[0204] When a detection device including a sensor for detecting
inclination, such as a gyroscope or an acceleration sensor, is
provided inside the mobile phone 7400, display on the screen of the
display portion 7402 can be automatically switched by determining
the orientation of the mobile phone 7400 (whether the mobile phone
is placed horizontally or vertically for a landscape mode or a
portrait mode).
[0205] The screen modes are switched by touching the display
portion 7402 or operating the operation button 7403 of the housing
7401. The screen modes can also be switched depending on the kind
of an image displayed on the display portion 7402. For example,
when a signal of an image displayed on the display portion is a
signal of moving image data, the screen mode is switched to the
display mode. When the signal is a signal of text data, the screen
mode is switched to the input mode.
[0206] Moreover, in the input mode, when input by touching the
display portion 7402 is not performed for a certain period while a
signal detected by an optical sensor in the display portion 7402 is
detected, the screen mode may be controlled so as to be switched
from the input mode to the display mode.
[0207] The display portion 7402 may function as an image sensor.
For example, an image of a palm print, a fingerprint, or the like
is taken when the display portion 7402 is touched with the palm or
the finger, whereby personal authentication can be performed.
Further, by providing a backlight or a sensing light source which
emits near-infrared light in the display portion, an image of a
finger vein, a palm vein, or the like can be taken.
[0208] As described above, the electronic devices can be obtained
using the light-emitting device that includes the light-emitting
element of one embodiment of the present invention. Note that the
light-emitting device can be used for electronic devices in a
variety of fields without being limited to the electronic devices
described in this embodiment.
[0209] Note that the structure described in this embodiment can be
combined as appropriate with any of the structures described in
other embodiments.
Embodiment 7
[0210] In this embodiment, examples of a lighting device and an
electronic device to each of which a light-emitting element
including the organometallic iridium complex of one embodiment of
the present invention or a light-emitting device including the
light-emitting element is applied are described with reference to
FIGS. 8A to 8C.
[0211] FIG. 8A illustrates an example in which the light-emitting
device is used as an indoor lighting device 8001. Since the
light-emitting device can have a large area, it can be used for a
lighting device having a large area. In addition, a lighting device
8002 in which a light-emitting region has a curved surface can also
be obtained with the use of a housing with a curved surface. A
light-emitting element included in the light-emitting device
described in this embodiment is in a thin film form, which allows
the housing to be designed more freely. Therefore, the lighting
device can be elaborately designed in a variety of ways. Further, a
wall of the room may be provided with a large-sized lighting device
8003.
[0212] Moreover, when the light-emitting device is used for a table
by being used as a surface of a table, a lighting device 8004 which
has a function as a table can be obtained. When the light-emitting
device is used as part of other furniture, a lighting device which
has a function as the furniture can be obtained.
[0213] FIG. 8B is a perspective view illustrating one surface of a
mobile phone, and FIG. 8C is a perspective view illustrating the
other surface of the mobile phone. A mobile phone 8100 has a
housing 8102 in which a display portion 8104, a camera 8106, an
illumination device 8108, and the like are incorporated. The
light-emitting device of one embodiment of the present invention
can be used for the display portion 8104 and the illumination
device 8108.
[0214] The illumination device 8108 that includes the
light-emitting element containing the organometallic iridium
complex of one embodiment of the present invention functions as a
planar light source. Thus, unlike a point light source typified by
an LED, the illumination device 8108 can provide light emission
with low directivity. When the illumination device 8108 and the
camera 8106 are used in combination, for example, imaging can be
performed by the camera 8106 with the illumination device 8108
lighting or flashing. Because the illumination device 8108
functions as a planar light source, a photograph as if taken under
natural light can be taken.
[0215] As described above, it is possible to provide various
lighting devices and electronic devices to which the light-emitting
element including the organometallic iridium complex of one
embodiment of the present invention or the light-emitting device
including the light-emitting element is applied. Note that such
lighting devices and electronic devices are also embodiments of the
present invention.
[0216] Note that the structure described in this embodiment can be
combined as appropriate with any of the structures described in
other embodiments.
Example 1
Synthesis Example 1
[0217] In this example, a method for synthesizing
bis{2-[6-(2,6-dimethylphenyl)-4-pyrimidinyl-.kappa.N3]phenyl-.kappa.C}(2,-
4-pentanedionato-.kappa.O,O') iridium(III) (abbreviation:
Ir(ppm-dmp).sub.2(acac)), which is an organometallic iridium
complex of one embodiment of the present invention represented by
Structural Formula (100) in Embodiment 1, is described. The
structure of Ir(ppm-dmp).sub.2(acac) is shown below.
##STR00039##
Step 1: Synthesis of 4-chloro-6-phenylpyrimidine
[0218] First, 5.0 g of 4,6-dichloropyrimidine, 4.9 g of
phenylboronic acid, 7.1 g of sodium carbonate, 0.34 g of
bis(triphenylphosphine)palladium(II) dichloride, namely
PdCl.sub.2(PPh.sub.3).sub.2, 20 mL of acetonitrile, and 20 mL of
water were put into a 100-mL round-bottom flask equipped with a
reflux pipe, and the air in the flask was replaced with argon.
Then, heating was performed by irradiation with microwaves (2.45
GHz, 100 W) for 1 hour. An organic layer was extracted from the
obtained mixture with the use of dichloromethane and was washed
with water and saturated brine. Magnesium sulfate was added and
gravity filtration was performed. The solvent in the obtained
filtrate was distilled off, and the given residue was purified by
flash column chromatography using dichloromethane as a developing
solvent, whereby 1.6 g of the objective substance was obtained
(yield: 23%, a pale yellow solid). Note that the irradiation with
microwaves was performed using a microwave synthesis system
(Discover, manufactured by CEM Corporation). A synthesis scheme of
Step 1 is shown in (a-1) below.
##STR00040##
Step 2: Synthesis of 4-phenyl-6-(2,6-dimethylphenyl)pyrimidine
(abbreviation: Hppm-dmp)
[0219] Next, 1.6 g of 4-chloro-6-phenylpyrimidine synthesized in
Step 1, 1.5 g of 2,6-dimethylphenylboronic acid, 1.8 g of sodium
carbonate, 59 mg of PdCl.sub.2(PPh.sub.3).sub.2, 20 mL of
N,N-dimethylformamide (abbreviation: DMF), and 20 mL of water were
put into a 100-mL round-bottom flask, and the air in the flask was
replaced with argon. Then, heating was performed by irradiation
with microwaves (2.45 GHz, 100 W) for 2 hours. An organic layer was
extracted from the obtained mixture with the use of
dichloromethane, and was washed with water and saturated brine.
Magnesium sulfate was added and gravity filtration was performed. A
solvent in the obtained filtrate was distilled off, and the given
residue was purified by flash column chromatography using a mixed
solvent of ethyl acetate and hexane (ethyl acetate: hexane=1:5) as
a developing solvent, whereby 0.50 g of the objective substance,
Hppm-dmp (abbreviation) was obtained (yield: 23%, a pale yellow
oily substance). A synthesis scheme of Step 2 is shown in (a-2)
below.
##STR00041##
Step 3: Synthesis of di-.mu.-chloro-tetrakis
{2-[6-(2,6-dimethylphenyl)-4-pyrimidinyl-.kappa.N3]phenyl-.kappa.C}diirid-
ium(III) (abbreviation: [Ir(ppm-dmp).sub.2Cl].sub.2)
[0220] Into a 100-mL round-bottom flask were put 1.0 g of Hppm-dmp
(abbreviation) synthesized in Step 2, 0.57 g of iridium(III)
chloride hydrate, 20 mL of 2-ethoxyethanol, and 20 mL of water, and
the air in the flask was replaced with argon. Then, heating was
performed by irradiation with microwaves (2.45 GHz, 100 W) for 3
hours. The obtained mixture was suction-filtered using methanol,
whereby 1.1 g of the objective substance,
[Ir(ppm-dmp).sub.2Cl].sub.2 (abbreviation) was obtained (yield:
74%, an orange solid). A synthesis scheme of Step 3 is shown in
(a-3) below.
##STR00042##
Step 4: Synthesis of
bis{2-[6-(2,6-dimethylphenyl)-4-pyrimidinyl-.kappa.N3]phenyl-.kappa.C}(2,-
4-pentanedionato-.kappa.O,O') iridium(III) (abbreviation:
Ir(ppm-dmp).sub.2(acac))
[0221] Into a 100-mL round-bottom flask equipped with a reflux pipe
were put 1.1 g of [Ir(ppm-dmp).sub.2Cl].sub.2 (abbreviation)
synthesized in Step 3, 0.77 g of sodium carbonate, 0.23 g of
acetylacetone (abbreviation: Hacac), and 30 mL of 2-ethoxyethanol,
and the air in the flask was replaced with argon. Then, heating was
performed by irradiation with microwaves (2.45 GHz, 120 W) for 2
hours. The obtained mixture was suction-filtrated using methanol,
and a solvent of the filtrate was distilled off. The obtained
residue was purified by flash column chromatography using a mixed
solvent of ethyl acetate and hexane (ethyl acetate: hexane=1:5) as
a developing solvent, and recrystallization was performed using
hexane, whereby an organometallic iridium complex of one embodiment
of the present invention, Ir(ppm-dmp).sub.2(acac), was obtained
(yield: 59%, an orange powdered solid). By a train sublimation
method, 0.21 g of the obtained orange powdered solid was purified.
In the purification by sublimation, the solid was heated at
240.degree. C. under a pressure of 2.7 Pa with an argon flow rate
of 5.0 mL/min. Thus, an orange solid, which was an objective
substance, was obtained in a yield of 48%. A synthesis scheme of
Step 4 is shown in (a-4) below.
##STR00043##
[0222] An analysis result by nuclear magnetic resonance
spectrometry (.sup.1H-NMR) of the orange solid obtained in Step 4
is described below. The .sup.1H NMR chart is shown in FIG. 9. The
results reveal that Ir(ppm-dmp).sub.2(acac), which is the
organometallic iridium complex of one embodiment of the present
invention represented by Structural Formula (100), was obtained in
Synthesis Example 1.
[0223] .sup.1H-NMR. .delta. (CDCl.sub.3): 1.85 (s, 6H), 2.26 (s,
12H), 5.35 (s, 1H), 6.46-6.48 (dd, 2H), 6.83-6.90 (dm, 4H),
7.20-7.22 (d, 4H), 7.29-7.32 (t, 2H), 7.63-7.65 (dd, 2H), 7.72 (ds,
2H), 9.24 (ds, 2H).
[0224] Next, an ultraviolet-visible absorption spectrum
(hereinafter, simply referred to as an "absorption spectrum") and
an emission spectrum of a dichloromethane solution of
Ir(ppm-dmp).sub.2(acac) were measured. The measurement of the
absorption spectrum was conducted at room temperature, for which an
ultraviolet-visible light spectrophotometer (V550 type manufactured
by Japan Spectroscopy Corporation) was used and the dichloromethane
solution (0.090 mmol/L) was put in a quartz cell. In addition, the
measurement of the emission spectrum was conducted at room
temperature, for which a fluorescence spectrophotometer (FS920
manufactured by Hamamatsu Photonics K. K.) was used and the
degassed dichloromethane solution (0.090 mmol/L) was put in a
quartz cell. Measurement results of the obtained absorption and
emission spectra are shown in FIG. 10, in which the horizontal axis
represents wavelength and the vertical axes represent absorption
intensity and emission intensity. In FIG. 10 where there are two
solid lines, the thin line represents the absorption spectrum and
the thick line represents the emission spectrum. Note that the
absorption spectrum in FIG. 10 is the results obtained in such a
way that the absorption spectrum measured by putting only
dichloromethane in a quartz cell was subtracted from the absorption
spectrum measured by putting the dichloromethane solution (0.090
mmol/L) in a quartz cell.
[0225] As shown in FIG. 10, Ir(ppm-dmp).sub.2(acac), the
organometallic iridium complex of one embodiment of the present
invention, has an emission peak at 553 nm, and yellow light
emission was observed from the dichloromethane solution.
[0226] Note that the structure described in this example can be
combined as appropriate with any of the structures described in
other embodiments and examples.
Example 2
Synthesis Example 2
[0227] In this synthesis example, an example of synthesizing
bis{2-[6-(2-tert-butylphenyl)-4-pyrimidinyl-.kappa.N3]phenyl-.kappa.C}(2,-
4-pentanedionato-.kappa..sup.2O,O') iridium(III) (abbreviation:
Ir(ppm-tBup).sub.2(acac)), which is an organometallic iridium
complex of one embodiment of the present invention represented by
Structural Formula (134) in Embodiment 1, is specifically
described. The structure of Ir(ppm-tBup).sub.2(acac) is shown
below.
##STR00044##
Step 1: Synthesis of 4-(2-tert-butylphenyl)-6-phenylpyrimidine
(abbreviation: Hppm-tBup)
[0228] First, 1.0 g of 4-chloro-6-phenylpyrimidine, 1.1 g of
2-tert-butylphenylboronic acid, 4.0 g of potassium phosphate, 39 mL
of toluene, and 3.9 mL of water were put in a three-neck flask
equipped with a reflux pipe, and the air in the flask was replaced
with nitrogen. In this container were added 48 mg of
bis(dibenzylideneacetone)palladium(0), namely Pd.sub.2(dba).sub.3,
and 190 mg of tris(2,6-dimethoxyphenyl)phosphine, and heating was
performed at 100.degree. C. for 7 hours. Then, 24 mg of
Pd.sub.2(dba).sub.3 and 46 mg of tris(2,6-dimethoxyphenyl)phosphine
were added and heating was performed at 100.degree. C. for 17
hours. After that, 12 mg of palladium acetate and 44 mg of
2-dicyclohexylphosphino-2',6'-dimethoxybiphenyl (abbreviation:
S-Phos) were added and heating was performed at 100.degree. C. for
15 hours. Furthermore, 5.9 mg of palladium acetate and 27 mg of
S-Phos (abbreviation) were added and heating was performed at
100.degree. C. for 8 hours. Then, 0.10 g of
2-tert-butylphenylboronic acid, 2.0 g of potassium phosphate, 13 mg
of palladium acetate, and 12 mg of S-Phos (abbreviation) were added
and heating was performed at 100.degree. C. for 21 hours. An
organic layer was extracted from the obtained mixture with the use
of ethyl acetate and was washed with saturated brine. Magnesium
sulfate was added and the mixture was subjected to filtration. The
solvent in the filtrate was distilled off to give a residue. The
residue was purified by neutral silica gel column chromatography
using a mixed solvent of ethyl acetate and hexane in a ratio of 1:4
as a developing solvent, so that 0.27 g of Hppm-tBup (abbreviation)
that is an objective substance was obtained as a yellowish white
solid in a yield of 18%. A synthesis scheme of Step 1 is shown in
(b-1) below.
##STR00045##
Step 2: Synthesis of
di-.mu.-chloro-tetrakis{2-[6-(2-tert-butylphenyl)-4-pyrimidinyl-.kappa.N3-
]phenyl-.kappa.C}diiridium(III) (abbreviation:
[Ir(ppm-tBup).sub.2Cl].sub.2)
[0229] Next, 0.27 g of Hppm-tBup (abbreviation) obtained by the
synthesis method in Step 1, 0.14 g of iridium(III) chloride
hydrate, 4.7 mL of 2-ethoxyethanol, and 1.6 mL of water were put in
a round-bottom flask equipped with a reflux pipe, and the mixture
was heated by being irradiated with microwaves (2.45 GHz, 100 W)
for 20 minutes while being bubbled with argon. The resulting
mixture was subjected to filtration and washing using hexane was
performed; thus, 300 mg of [Ir(ppm-tBup).sub.2Cl].sub.2
(abbreviation) that is an objective substance was obtained as a
dark orange solid in a yield of 80%. Note that the irradiation with
microwaves was performed using a microwave synthesis system
(Discover, manufactured by CEM Corporation). A synthesis scheme of
Step 2 is shown in (b-2) below.
##STR00046##
Step 3: Synthesis of
bis{[6-(2-tert-butylphenyl)-4-pyrimidinyl-.kappa.N3]phenyl-.kappa.C}(2,4--
pentanedionato-.kappa..sup.2O,O') iridium(III) (abbreviation:
Ir(ppm-tBup).sub.2(acac))
[0230] Next, 300 mg of [Ir(ppm-tBup).sub.2Cl].sub.2 (abbreviation)
obtained in Step 2, 57 mg of acetylacetone (abbreviation: Hacac),
200 mg of sodium carbonate, and 2 mL of 2-ethoxyethanol were put in
a flask, and the mixture was irradiated with microwaves (2.45 GHz,
80 W) for 7 minutes while being bubbled with argon. The solvent in
the obtained mixture was distilled off, and the obtained residue
was purified by flash column chromatography using a mixed solvent
of ethyl acetate and hexane in a ratio of 1:5 as a developing
solvent. The solvent was distilled off, and the obtained residue
was purified by flash column chromatography (amine-modified silica
gel) using a mixed solvent of ethyl acetate and hexane in a ratio
of 1:5 as a developing solvent. Thus, Ir(ppm-tBup).sub.2(acac),
which is the organometallic iridium complex of one embodiment of
the present invention, was obtained as an orange powdered solid in
a yield of 5%. A synthesis scheme of Step 3 is shown in (b-3)
below.
##STR00047##
[0231] An analysis result by nuclear magnetic resonance
spectrometry (.sup.1H-NMR) of the orange powdered solid obtained in
Step 3 is described below. The .sup.1H NMR chart is shown in FIG.
17. The results reveal that Ir(ppm-tBup).sub.2(acac), which is the
organometallic complex of one embodiment of the present invention
represented by Structural Formula (134), was obtained in this
synthesis example. Note that the peaks observed at 0.88-0.89 and
1.25-1.29 in the .sup.1H-NMR chart were derived from the hexane
solvent.
[0232] .sup.1H-NMR. .delta. (CDCl.sub.3): 1.38 (s, 18H), 1.84 (s,
6H), 5.32 (s, 1H), 6.52 (d, 2H), 6.82-6.85 (dt, 2H), 6.87-6.90 (t,
2H), 7.29 (dd, 2H), 7.34-7.37 (dt, 2H), 7.45-7.49 (dt, 2H),
7.64-7.68 (dt, 4H), 7.82 (ds, 2H), 9.16 (ds, 2H).
[0233] Next, an absorption spectrum and an emission spectrum of a
deoxidized dichloromethane solution of Ir(ppm-tBup).sub.2(acac)
were measured. The measurement of the absorption spectrum was
conducted at room temperature, for which an ultraviolet-visible
light spectrophotometer (V550 type manufactured by Japan
Spectroscopy Corporation) was used and the dichloromethane solution
(0.011 mmol/L) was put in a quartz cell. In addition, the
measurement of the emission spectrum was conducted at room
temperature, for which an absolute PL quantum yield measurement
system (C11347-01 manufactured by Hamamatsu Photonics K. K.) was
used. The deoxidized dichloromethane solution (0.011 mmol/L) was
sealed in a quartz cell under a nitrogen atmosphere in a glove box
(LABstar M13 (1250/780)) manufactured by Bright Co., Ltd.
Measurement results of the obtained absorption and emission spectra
are shown in FIG. 18, in which the horizontal axis represents
wavelength and the vertical axes represent absorption intensity and
emission intensity. In FIG. 18 where there are two solid lines, the
thin line represents the absorption spectrum and the thick line
represents the emission spectrum. Note that the absorption spectrum
in FIG. 18 is the results obtained in such a way that the
absorption spectrum measured by putting only dichloromethane in a
quartz cell was subtracted from the absorption spectrum measured by
putting the dichloromethane solution (0.011 mmol/L) in a quartz
cell.
[0234] As shown in FIG. 18, Ir(ppm-tBup).sub.2(acac), the
organometallic complex of one embodiment of the present invention,
has an emission peak at 553 nm, and yellow light emission was
observed from the dichloromethane solution.
[0235] Note that the structure described in this example can be
combined as appropriate with any of the structures described in
other embodiments and examples.
Example 3
[0236] In this example, a light-emitting element 1, a comparative
light-emitting element 2, and a comparative light-emitting element
3 were fabricated, and characteristics of these elements were
measured. Light-emitting layers of the light-emitting element 1,
the comparative light-emitting element 2, and the comparative
light-emitting element 3 were respectively formed using
Ir(ppm-dmp).sub.2(acac) (Structural Formula (100)) that is the
organometallic iridium complex of one embodiment of the present
invention synthesized in Example 1,
(acetylacetonato)bis[5-methyl-6-(2-methylphenyl)-4-phenylpyrimidinato]iri-
dium(III) (another name:
bis{2-[5-methyl-6-(2-methylphenyl)-4-pyrimidinyl-.kappa.N3]phenyl-.kappa.-
C}(2,4-pentanedionato-.kappa..sup.2O,O')iridium(III))
(abbreviation: Ir(mpmppm).sub.2(acac)) (Structural Formula (502))
that is a comparative organometallic iridium complex, and
(acetylacetonato)bis(4,6-diphenylpyrimidinato)iridium(III)
(abbreviation: Ir(dppm).sub.2(acac)) (Structural Formula (500))
that is a comparative organometallic iridium complex. Chemical
formulae of materials used in this example are shown below.
##STR00048## ##STR00049##
[0237] A method for fabricating the light-emitting element 1 is
described with reference to FIG. 11.
(Light-Emitting Element 1)
[0238] First, an indium oxide-tin oxide compound containing silicon
or silicon oxide (ITO-SiO.sub.2, hereinafter abbreviated to ITSO)
was deposited by a sputtering method on a substrate 1100, so that a
first electrode 1101 was formed. Note that the composition ratio of
In.sub.2O.sub.3 to SnO.sub.2 and SiO.sub.2 in the target used was
85:10:5 [wt %]. The thickness of the first electrode 1101 was 110
nm and the electrode area was 2 mm.times.2 mm. Here, the first
electrode 1101 functions as an anode of the light-emitting
element.
[0239] Next, as pretreatment for forming the light-emitting element
over the substrate 1100, the surface of the substrate was washed
with water, baked at 200.degree. C. for 1 hour, and subjected to UV
ozone treatment for 370 seconds.
[0240] After that, the substrate 1100 was transferred into a vacuum
evaporation apparatus where the pressure had been reduced to
approximately 10.sup.-4 Pa, and subjected to vacuum baking at
170.degree. C. for 30 minutes in a heating chamber of the vacuum
evaporation apparatus, and then the substrate 1100 was cooled down
for about 30 minutes.
[0241] Next, the substrate 1100 was fixed to a substrate holder in
the vacuum evaporation apparatus so that the surface on which the
first electrode 1101 was provided faced downward. The pressure in
the vacuum evaporation apparatus was reduced to about 10.sup.-4 Pa.
Then, 1,3,5-tri(dibenzothiophen-4-yl)benzene (abbreviation:
DBT3P-II) and molybdenum oxide were deposited by co-evaporation
with a mass ratio of DBT3P-II to molybdenum oxide being 2:1, so
that a hole-injection layer 1111 was formed on the first electrode
1101. The thickness of the hole-injection layer 1111 was set to 20
nm. Note that a co-evaporation method is an evaporation method in
which a plurality of different substances are concurrently
vaporized from respective different evaporation sources.
[0242] Next, on the hole-injection layer 1111,
4-phenyl-4'-(9-phenylfluoren-9-yl)triphenylamine (abbreviation:
BPAFLP) was deposited by evaporation to a thickness of 20 nm, so
that a hole-transport layer 1112 was formed.
[0243] Next, a light-emitting layer 1113 was formed on the
hole-transport layer 1112. For the light-emitting layer 1113,
2-[3'-(dibenzothiophen-4-yl)biphenyl-3-yl]dibenzo[f,h]quinoxaline
(abbreviation: 2mDBTBPDBq-II),
N-(1,1'-biphenyl-4-yl)-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-9,9-dimeth-
yl-9H-fluoren-2-amine (abbreviation: PCBBiF), and
Ir(ppm-dmp).sub.2(acac) deposited by co-evaporation with a mass
ratio of 2mDBTBPDBq-II to PCBBiF and Ir(ppm-dmp).sub.2(acac) being
0.8:0.2:0.05. The thickness of the light-emitting layer 1113 was 40
nm.
[0244] Note that in the light-emitting layer 1113 of the
light-emitting element 1, 2mDBTBPDBq-II served as a host material,
PCBBiF served as a secondary host material, and
Ir(ppm-dmp).sub.2(acac) served as a guest material (dopant).
[0245] Then, on the light-emitting layer 1113, 2mDBTBPDBq-II was
deposited by evaporation to a thickness of 15 nm and then
bathophenanthroline (abbreviation: Bphen) was deposited by
evaporation to a thickness of 10 nm, whereby an electron-transport
layer 1114 was formed. Furthermore, lithium fluoride was deposited
by evaporation to a thickness of 1 nm on the electron-transport
layer 1114, whereby an electron-injection layer 1115 was
formed.
[0246] Finally, aluminum was deposited by evaporation to a
thickness of 200 nm on the electron-injection layer 1115, whereby a
second electrode 1103 serving as a cathode was formed. Through the
above-described steps, the light-emitting element 1 was
fabricated.
[0247] Next, methods for fabricating the comparative light-emitting
elements 2 and 3 are described.
(Comparative Light-Emitting Element 2)
[0248] The comparative light-emitting element 2 is different from
the light-emitting element 1 in the structure of the light-emitting
layer 1113. Only the structure different from the light-emitting
element 1 is described below.
[0249] For the light-emitting layer 1113, 2mDBTBPDBq-II, PCBBiF,
and bis
{2-[5-methyl-6-(2-methylphenyl)-4-pyrimidinyl-.kappa.N3]phenyl-.kappa.C}(-
2,4-pentanedionato-.kappa..sup.2O,O')iridium(III) (abbreviation:
Ir(mpmppm).sub.2(acac)) deposited by co-evaporation with a mass
ratio of 2mDBTBPDBq-II to PCBBiF and Ir(mpmppm).sub.2(acac) being
0.8:0.2:0.05. The thickness of the light-emitting layer 1113 was 40
nm.
[0250] Note that in the light-emitting layer 1113 of the
comparative light-emitting element 2, 2mDBTBPDBq-II served as a
host material, PCBBiF served as an assist material, and
Ir(mpmppm).sub.2(acac) served as a guest material (dopant).
(Comparative Light-Emitting Element 3)
[0251] The comparative light-emitting element 3 is different from
the light-emitting element 1 in the structures of the
light-emitting layer 1113 and the electron-transport layer 1114.
Only the structures different from the light-emitting element 1 are
described below.
[0252] For the light-emitting layer 1113, 2mDBTBPDBq-II, PCBBiF,
and (acetylacetonato)bis(4,6-diphenylpyrimidinato)iridium(III)
(abbreviation: Ir(dppm).sub.2(acac)) were deposited by
co-evaporation to a thickness of 20 nm with a mass ratio of
2mDBTBPDBq-II to PCBBiF and Ir(dppm).sub.2(acac) being
0.7:0.3:0.05; then, 2mDBTBPDBq-II, PCBBiF, and Ir(dppm).sub.2(acac)
were deposited by co-evaporation to a thickness of 20 nm with a
mass ratio of 2mDBTBPDBq-II to PCBBiF and Ir(dppm).sub.2(acac)
being 0.7:0.3:0.05.
[0253] Note that in the light-emitting layer 1113 of the
comparative light-emitting element 3, 2mDBTBPDBq-II served as a
host material, PCBBiF served as an assist material, and
Ir(dppm).sub.2(acac) served as a guest material (dopant).
[0254] Note that in all the above evaporation steps, evaporation
was performed by a resistance-heating method.
[0255] Since the light-emitting element 1, the comparative
light-emitting element 2, and the comparative light-emitting
element 3 use the respective guest materials (dopants), the
structure of the light-emitting layer 1113 and the
electron-transport layer 1114 were optimized. Table 2 shows element
structures of the light-emitting element 1, the comparative
light-emitting element 2, and the comparative light-emitting
element 3 formed as described above.
TABLE-US-00002 TABLE 2 Hole- Light- Electron- First Hole-injeciton
transport emitting Electron-transport injection Second electrode
layer layer layer layer layer electrode Light-emitting ITSO
DBT3P-II:MoO.sub.x BPAFLP *1) 2mDBTBPDBq-II Bphen LiF Al element 1
(110 nm) (2:1 20 nm) (20 nm) (15 nm) (10 nm) (1 nm) (200 nm)
Comparative ITSO DBT3P-II:MoO.sub.x BPAFLP *2) 2mDBTBPDBq-II Bphen
LiF Al light-emitting (110 nm) (2:1 20 nm) (20 nm) (15 nm) (10 nm)
(1 nm) (200 nm) element 2 Comparative ITSO DBT3P-II:MoO.sub.x
BPAFLP *3) 2mDBTBPDBq-II Bphen LiF Al light-emitting (110 nm) (2:1
20 nm) (20 nm) (20 nm) (10 nm) (1 nm) (200 nm) element 3 *1)
2mDBTBPDBq-II:PCBBiF:Ir(ppm-dmp).sub.2(acac) (0.8:0.2:0.05 40 nm)
*2) 2mDBTBPDBq-II:PCBBiF:Ir(mpmppm).sub.2(acac) (0.8:0.2:0.05 40
nm) *3)
2mDBTBPDBq-II:PCBBiF:Ir(dppm).sub.2(acac)\2mDBTBPDBq-II:PCBBiF:Ir(dppm-
).sub.2(acac) ((0.7:0.3:0.05 20 nm)\(0.8:0.2:0.05 20 nm))
[0256] Then, in a glove box containing a nitrogen atmosphere, the
light-emitting element 1, the comparative light-emitting element 2,
and the comparative light-emitting element 3 were sealed so as not
to be exposed to the air (specifically, a sealant was applied onto
an outer edge of the elements and heat treatment was performed at
80.degree. C. for 1 hour at the time of sealing). After that, the
operating characteristics of the light-emitting element 1, the
comparative light-emitting element 2, and the comparative
light-emitting element 3 were measured. Note that the measurement
was carried out at room temperature (kept at 25.degree. C.).
[0257] FIG. 12 shows voltage-luminance characteristics of the
light-emitting element 1, the comparative light-emitting element 2,
and the comparative light-emitting element 3. In FIG. 12, the
horizontal axis represents voltage (V) and the vertical axis
represents luminance (cd/m.sup.2). Further, FIG. 13 shows
luminance-current efficiency characteristics of the light-emitting
element 1, the comparative light-emitting element 2, and the
comparative light-emitting element 3. In FIG. 13, the horizontal
axis represents luminance (cd/m.sup.2) and the vertical axis
represents current efficiency (cd/A). FIG. 14 shows voltage-current
characteristics of the light-emitting element 1, the comparative
light-emitting element 2, and the comparative light-emitting
element 3. In FIG. 14, the horizontal axis represents voltage (V)
and the vertical axis represents current (mA). FIG. 15 shows
luminance-external quantum efficiency characteristics of the
light-emitting element 1, the comparative light-emitting element 2,
and the comparative light-emitting element 3. In FIG. 15, the
horizontal axis represents luminance (cd/m.sup.2) and the vertical
axis represents external quantum efficiency (%).
[0258] The results in FIG. 13 and FIG. 15 show that the
light-emitting element 1 of one embodiment of the present invention
has higher current efficiency and external quantum efficiency than
the comparative light-emitting element 2 and the comparative
light-emitting element 3.
[0259] Table 3 shows the characteristics of the light-emitting
element 1, the comparative light-emitting element 2, and the
comparative light-emitting element 3.
TABLE-US-00003 TABLE 3 CIA External Current chromaticity Current
Power quantum Voltage Current density coordinates Luminance
efficiency efficiency efficiency (V) (mA) (mA/cm.sup.2) (x, y)
(cd/m.sup.2) (cd/A) (lm/W) (%) Light-emitting 2.8 0.037 0.9 (0.44,
0.55) 1200 130 140 33 element 1 Comparative 2.8 0.046 1.2 (0.49,
0.50) 1100 94 110 28 light-emitting element 2 Comparative 2.8 0.027
0.7 (0.55, 0.45) 607 91 102 32 light-emitting element 3
[0260] FIG. 16 shows emission spectra of the light-emitting element
1, the comparative light-emitting element 2, and the comparative
light-emitting element 3 when current was supplied thereto at a
current density of 2.5 mA/cm.sup.2. As shown in FIG. 16, the
emission spectra of the light-emitting element 1, the comparative
light-emitting element 2, and the comparative light-emitting
element 3 have peaks at 553 nm, 563 nm, and 579 nm,
respectively.
[0261] From the CIE chromaticity coordinates (x, y) in Table 3 and
the emission spectra in FIG. 16, it was found that the
light-emitting element 1, the comparative light-emitting element 2,
and the comparative light-emitting element 3 emit light derived
from the dopants.
[0262] The above-described results show that the emission spectrum
of the light-emitting element 1 of one embodiment of the present
invention is located on a shorter wavelength side than the emission
spectrum of the comparative light-emitting element 2 and that of
the comparative light-emitting element 3. Because the emission
spectrum of the light-emitting element 1 peaks at 553 nm, light
emitted from the light-emitting element 1 has a higher luminosity
factor than light emitted from the comparative light-emitting
element 2 and light emitted from the comparative light-emitting
element 3. It is also shown that the light-emitting element 1 of
one embodiment of the present invention has high luminance and
exhibits favorable current efficiency characteristics. Moreover, it
can be found that the light-emitting element 1 emits yellow light
with excellent color purity.
[0263] Calculation of the dihedral angle between the pyrimidine
ring and the phenyl group at the 6-position of the pyrimidine ring
was performed on Ir(ppm-dmp).sub.2(acac), Ir(mpmppm).sub.2(acac),
and Ir(dppm).sub.2(acac) that were used as the light-emitting
substances in the light-emitting element 1, the comparative
light-emitting element 2, and the comparative light-emitting
element 3, respectively.
[0264] The calculation device and method that are described in
Embodiment 1 were used.
[0265] The results of calculation are shown in Table 4.
TABLE-US-00004 TABLE 4 Material Dihedral angle (.degree.) Element
Ir(ppm-dmp).sub.2(acac) 70 Light-emitting element 1
Ir(mpmppm).sub.2(acac) 64 Comparative light-emitting element 2
Ir(dppm).sub.2(acac) 18 Comparative light-emitting element 3
[0266] As shown in Table 4, the dihedral angle between the
pyrimidine ring and the phenyl group at the 6-position of the
pyrimidine ring is larger in Ir(ppm-dmp).sub.2(acac), which was
used in the light-emitting element 1 of one embodiment of the
present invention, than in Ir(mpmppm).sub.2(acac) and
Ir(dppm).sub.2(acac), which were respectively used in the
comparative, light-emitting element 2 and the comparative
light-emitting element 3. Consequently, in the organometallic
iridium complex of one embodiment of the present invention, a twist
is formed owing to steric hindrance and extension of
.pi.-conjugation thus can be inhibited.
[0267] Note that the structure described in this example can be
combined as appropriate with any of the structures described in
other embodiments and examples.
REFERENCE NUMERALS
[0268] 101: first electrode, 102: EL layer, 103: second electrode,
111: hole-injection layer, 112: hole-transport layer, 113:
light-emitting layer, 114: electron-transport layer, 115:
electron-injection layer, 116: charge generation layer, 201: first
electrode, 202: second electrode, 203: EL layer, 204:
light-emitting layer, 205: phosphorescent compound, 206: first
organic compound, 207: second organic compound, 210: first layer,
212: second layer, 301: first electrode, 302: EL layer, 304: second
electrode, 305: charge generation layer, 401: element substrate,
402: pixel portion, 403: driver circuit portion, 404a: driver
circuit portion, 404b: driver circuit portion, 405: sealant, 406:
sealing substrate, 407: lead wiring, 408: FPC, 409: FET, 410: FET,
411: FET, 412: FET, 413: first electrode, 414: insulator, 415: EL
layer, 416: second electrode, 417: light-emitting element, 418:
space, 1100: substrate, 1101: first electrode, 1103: second
electrode, 1111: hole-injection layer, 1112: hole-transport layer,
1113: light-emitting layer, 1114: electron-transport layer, 1115:
electron-injection layer, 7100: television set, 7101: housing,
7103: display portion, 7105: stand, 7107: display portion, 7109:
operation key, 7110: remote controller, 7201: main body, 7202:
housing, 7203: display portion, 7204: keyboard, 7205: external
connection port, 7206: pointing device, 7302: housing, 7304:
display panel, 7305: icon, 7306: icon, 7311: operation button,
7312: operation button, 7313: connection terminal, 7321: band,
7322: clasp, 7400: mobile phone, 7401: housing, 7402: display
portion, 7403: button, 7404: external connection portion, 7405:
speaker, 7406: microphone, 7407: camera, 8001: lighting device,
8002: lighting device, 8003: lighting device, 8004: lighting
device, 8100: mobile phone, 8102: housing, 8104: display portion,
8106: camera, and 8108: illumination device.
[0269] This application is based on Japanese Patent Application
serial no. 2013-189385 filed with Japan Patent Office on Sep. 12,
2013, the entire contents of which are hereby incorporated by
reference.
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