U.S. patent application number 11/401537 was filed with the patent office on 2006-08-10 for organometallic light-emitting material.
Invention is credited to Michael Chi-Wang Chan, Chi-Ming Che, Wei Lu.
Application Number | 20060175605 11/401537 |
Document ID | / |
Family ID | 23046962 |
Filed Date | 2006-08-10 |
United States Patent
Application |
20060175605 |
Kind Code |
A1 |
Che; Chi-Ming ; et
al. |
August 10, 2006 |
Organometallic light-emitting material
Abstract
Disclosed herein are novel light-emitting materials of Formula I
and II below. These new complexes are synthesized and found to be
sufficiently stable to allow sublimation and vacuum deposition.
These new emitters are electrophosphorescent and can be used in
organic light-emitting devices (OLEDs) for device elements capable
of emitting light of color ranging from orange to red with
high-efficiency and high-brightness. ##STR1## wherein E=Group 16
elements (including sulphur); M=Group 10 metal (including
platinum); R.sub.1-R.sub.14 are each independently selected from
the group consisting of hydrogen; halogen; alkyl; substituted
alkyl; aryl; substituted aryl, with substituents selected from the
group consisting of halogen, lower alkyl and recognized donor and
acceptor groups. R.sub.1 can also be selected from
(C.ident.C).sub.nR.sub.15, where (C.ident.C) represents a
carbon-carbon triple bond (acetylide group), n is selected from 1
to 10, and R.sub.15 is selected from alkyl, aryl, substituted aryl,
and tri(alkyl)silyl.
Inventors: |
Che; Chi-Ming; (Hong Kong,
CN) ; Lu; Wei; (Hong Kong, CN) ; Chan; Michael
Chi-Wang; (Hong Kong, CN) |
Correspondence
Address: |
BERKELEY LAW & TECHNOLOGY GROUP
1700NW 167TH PLACE
SUITE 240
BEAVERTON
OR
97006
US
|
Family ID: |
23046962 |
Appl. No.: |
11/401537 |
Filed: |
April 10, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10094384 |
Mar 8, 2002 |
7026480 |
|
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11401537 |
Apr 10, 2006 |
|
|
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60274142 |
Mar 8, 2001 |
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Current U.S.
Class: |
257/40 ; 313/504;
546/2 |
Current CPC
Class: |
C09K 2211/1092 20130101;
C09K 11/06 20130101; C09K 2211/1029 20130101; H01L 51/0081
20130101; H05B 33/14 20130101; Y10S 428/917 20130101; C09K 2211/10
20130101; H01L 51/006 20130101; H01L 51/5016 20130101; C09K
2211/185 20130101; C09K 2211/1007 20130101; H01L 51/0071 20130101;
H01L 51/0087 20130101; C07F 15/0086 20130101; C07F 15/0033
20130101 |
Class at
Publication: |
257/040 ;
546/002; 313/504 |
International
Class: |
C07F 15/00 20060101
C07F015/00; H01L 29/08 20060101 H01L029/08; H01J 1/62 20060101
H01J001/62 |
Claims
1-2. (canceled)
3. A light-emitting material for use as an emitter or dopant in an
organic light-emitting diode comprising a tridentate ligand which
is coordinated to platinum using one carbon and two nitrogen
atoms.
4. A light-emitting material for use as an emitter or dopant in an
organic light-emitting diode comprising a tridentate ligand which
is coordinated to platinum using a diimine group selected from
2,2'-bipyridine and substituted 2,2'-bipryidines, and deprotonated
aromatic group selected from phenyl, aryl and heteroatom-containing
aryl.
5-7. (canceled)
Description
RELATED APPLICATIONS
[0001] The subject application claims the priority of U.S.
provisional patent application No. 60/274,142, filed on Mar. 8,
2001.
FIELD OF THE INVENTION
[0002] This invention relates to light-emitting materials which are
discrete organometallic molecules in nature, which can be deposited
as a thin layer by vacuum deposition, and which can act as
electrophosphorescent emitters in high-efficiency and
high-brightness organic light-emitting devices (OLEDs).
BACKGROUND OF THE INVENTION
[0003] Tang and coworkers first reported on high-performance
organic light-emitting devices (OLEDs) in 1987 (Tang, C. W.; et al.
Appl. Phys. Lett. 51, 913 (1987)). Their discovery was based on
employing a multilayer structure containing an emitting layer and a
hole transport layer of a suitable organic substrate. Alq.sub.3
(q=deprotonated 8-hydroxyquinolinyl) was chosen as the emitting
material and proven to be of high-performance because (1) it can
form uniform thin films under 1000 .ANG. using vacuum deposition,
(2) it is a good charge carrier and (3) it exhibits strong
fluorescence. Since then, there has been a flourish of research on
OLEDs and materials used in these devices. Indeed, nearly every
large chemical company in the world with optoelectronic interests
has demonstrated some level of interest in OLEDs. Clearly, OLED
technology is heading directly and rapidly into the marketplace, as
suggested in a commercial report by Stanford Resources (by David E.
Mentley, "The Market Potential for Organic Light-Emitting Diode
Displays," Commercial Report, available at
http://www.stanfordresources.com). The attractiveness of OLEDs as
it challenges traditional technologies such as cathode ray tubes
(CRTs), liquid crystal displays (LCDs) and plasma displays is based
on many features and advantages, including:
[0004] Low operating voltage,
[0005] Thin, monolithic structure,
[0006] Emits, rather than modulates light,
[0007] Good luminous efficiency,
[0008] Full color potential, and
[0009] High contrast and resolution.
[0010] OLED is a device built with organic semiconductors from
which visible light can be emitted upon electrical stimulation. The
basic heterostructure of an OLED is described in FIG. 1.
[0011] The layers may be formed by evaporation, spin-casting or
chemical self-assembly. The thickness ranges from a few monolayers
(self-assembled films) to about 1000 to 2000 .ANG.. Such devices
whose structure is based on the use of layers of organic
optoelectronic materials generally rely on a common mechanism
leading to optical emission, namely, the radiative recombination of
a trapped charge. Under a DC bias, electrons are injected from a
cathode (usually Ca, Al, Mg--Ag) and holes are injected from an
anode (usually transparent indium tin oxide (ITO)) into the organic
materials, where they travel in the applied field across the
electron transporting layer (ETL) and the hole transporting layer
(HTL) respectively until they meet, preferably on molecules in the
emitting layer, and form a luminescent excited state (Frenkel
exciton) which, under certain conditions, experiences radiative
decay to give visible light. The electroluminescent material may be
present in a separate emitting layer between the ETL and the HTL in
what is referred as a multi-layer heterostructure. In some cases,
buffer layers and/or other functional layers are also incorporated
to improve the performance of the device. Alternatively, those
OLEDs in which the electroluminescent emitters are the same
materials that function either as the ETL or HTL are referred to as
single-layer heterostructures.
[0012] In addition to emissive materials that are present as the
predominant component in the charge carrier layers (HTL or ETL),
other efficient luminescent material(s) may be present in
relatively low concentrations as a dopant in these layers to
realize color tuning and efficiency improvement. Whenever a dopant
is present, the predominant material in the charge carrier layer
may be referred to as a host. Ideally, materials that are present
as hosts and dopant are matched so as to have a high level of
energy transfer from the host to the dopant, and to yield emission
with a relatively narrow band centered near selected spectral
region with high-efficiency and high-brightness.
[0013] While fluorescent emitters with high luminescence
efficiencies have been extensively applied as dopant in OLEDs,
phosphorescent emitters have been neglected in this domain.
However, the quantum efficiency of an electrofluorescence device is
limited by the low theoretical ratio of singlet exciton (25%)
compared to triplet exciton (75%) upon electron-hole recombination
from electrical excitation. In contrast, when phosphorescent
emitters are employed, the potentially high energy/electron
transfer from the hosts to the phosphorescent emitters may result
in significantly superior electroluminescent efficiency (Baldo, M.
A.; et al. Nature 395, 151 (1998) and Ma, Y. G.; et al. Synth. Met.
94, 245 (1998)). Several phosphorescent OLED systems have been
fabricated and have indeed proven to be of relative high-efficiency
and high-brightness.
[0014] It is desirable for OLEDs to be fabricated using materials
that provide electrophosphorescent emission corresponding to one of
the three primary colors, i.e., red, green and blue so that they
may be used as a component layer in full-color display devices. It
is also desirable that such materials are capable of being
deposited as thin films using vacuum deposition techniques, which
has been prove to be a common method for high-performance OLED
fabrication, so that the thickness of the emitting layer can be
precisely controlled.
[0015] Presently, the highest efficiencies and brightness have been
obtained with green electrophosphorescent devices (15.4.+-.0.2% for
external quantum efficiency and almost 100% for internal
efficiency, 10.sup.5 Cd/m.sup.2 for maximum luminance) using
Ir(ppy).sub.3 (ppy=deprotonated 2-phenylpyridine) as emitter
(Adachi, C.; et al. Appl. Phys. Lett. 77, 904 (2000)). An OLED
emitting saturated red light based on the electrophosphorescent
dopant Pt(OEP) (H.sub.2OEP=octaethylporphyrin) has also been
published and patented (Burrows, P.; et al. U.S. Pat. No.
6,048,630) but the maximum luminance is only around 500 Cd
m.sup.-2. A relevant patent is the use of the cyclometalated
platinum(II) complex Pt(thpy).sub.2 (thpy=deprotonated
2-(2-thioenyl)pyridine) as dopant and PVK (poly(N-vinyl)carbazole)
as host in a orange OLED (Lamansky, S.; et al. WO Pat. No.
00/57676). However, the Pt(I) complex used by the inventors was not
stable for sublimation or vacuum deposition, thus a spin-casting
method was applied, which led to higher driving voltages, quantum
efficiency of 0.11% and luminance of 100 Cd/m.sup.2 were obtained
at 22 V.
SUMMARY OF THE INVENTION
[0016] The present invention is directed to novel organometallic
light-emitting materials which may be used as electrophosphorescent
emitters or dopants in high-performance OLEDs. In particular, the
present invention is directed to the design, synthesis, properties
and applications of a family of phosphorescent emitters which, when
added in effective amounts to suitable host material, including
emissive compounds, electron transporting compounds and hole
transporting compounds, tune the color of emission in the near-red
range and enhance the device efficiency and brightness.
Furthermore, the thermal stability of these phosphorescent emitters
in the present invention are sufficient to allow sublimation, so
that they may be readily incorporated into devices using vacuum
deposition techniques, and hence high-performance
electrophosphorescent devices prepared entirely from
vacuum-deposited materials may be realized.
[0017] The family of electrophosphorescent emitters for use in the
present invention are acetylide (alkynyl) complexes of the Group 10
metals, including platinum, with chemical structures of either
Formula I or II: ##STR2##
[0018] wherein E=Group 16 elements (including sulphur); M=Group 10
metal (including platinum); R.sub.1-R.sub.14 are each independently
selected from the group consisting of hydrogen; halogen; alkyl;
substituted alkyl; aryl; substituted aryl, with substituents
selected from the group consisting of halogen, lower alkyl and
recognized donor and acceptor groups. R.sub.1 can also be selected
from (C.ident.C).sub.nR.sub.15, where (C.ident.C) represents a
carbon-carbon triple bond (acetylide group), n is selected from 1
to 10, and R.sub.15 is selected from alkyl, aryl, substituted aryl,
and tri(alkyl)silyl. Group 16 elements are also known as the Group
VIA elements. Group 10 elements also belong to Group VIIIB.
[0019] As established by thermogravimetric analysis, some of these
complexes are thermally stable up to .about.400.degree. C. These
complexes are good phosphorescent emitters and give strong orange
to red emissions (.lamda..sub.max 550-630 nm) in fluid solutions by
photo excitation and in OLEDs by electrical stimulation.
[0020] Generally, the present invention is directed to the
syntheses and OLED applications of the family of
electrophosphorescent emitters defined by Formula I and II. Our
claims include the synthetic method for these novel complexes as
well as their use as light-emitting material. These OLED
applications include OLEDs wherein these complexes are incorporated
as components either by vacuum deposition, spin-casting or other
device fabrication methods.
[0021] In the present invention, the light-emitting material for
use as an emitter or dopant in an OLED can comprise one or more
metal-acetylide (metal-alkynyl) groups. In alternative, the
light-emitting material for use as an emitter or dopant in an OLED
comprises one or more platinum-acetylide (platinum-alkynyl) groups.
In one embodiment, the light-emitting material for use as an
emitter or dopant in an OLED can comprises a platinum atom
coordinated by a tridentate ligand using one carbon and two
nitrogen atoms. In another embodiment, the light-emitting material
for use as an emitter or dopant in an OLED comprising a platinum
atom coordinated by a tridentate ligand bearing a deprotonated
phenyl carbonion and 2,2'-bipyridine.
[0022] In an exemplary embodiment, the light-emitting material for
use as an emitter or dopant in an OLED can have a chemical
structure represented by either Formula I or II: ##STR3## wherein
E=Group 16 elements (including sulphur); M=Group 10 metal
(including platinum); R.sub.1-R.sub.14 are each independently
selected from the group consisting of hydrogen; halogen; alkyl;
substituted alkyl; aryl; substituted aryl, with substituents
selected from the group consisting of halogen, lower alkyl and
recognized donor and acceptor groups. R.sub.1 can also be selected
from (C.ident.C).sub.nR.sub.15, where (C.ident.C) represents a
carbon-carbon triple bond (acetylide group), n is selected from 1
to 10, and R.sub.15 is selected from alkyl, aryl, substituted aryl,
and tri(alkyl)silyl.
[0023] In one embodiment, the light-emitting material can be
deposited as a thin layer by sublimation or vacuum deposition. In
another embodiment, the light-emitting material can be fabricated
into OLEDs using spin-coating or other methods.
BRIEF DESCRIPTION OF THE FIGURES
[0024] FIG. 1. General heterostructure of OLEDs.
[0025] FIG. 2. TGA curve of complex 2.
[0026] FIG. 3. TGA curve of complex 15.
[0027] FIG. 4. UV-vis absorption and emission spectra of complex 2
in CH.sub.2Cl.sub.2 at 298 K.
[0028] FIG. 5. UV-vis absorption and emission spectra of complex 15
in CH.sub.2Cl.sub.2 at 298 K.
[0029] FIG. 6. The heterostructure of OLEDs in present
invention.
[0030] FIG. 7. Electroluminescent spectrum, current-voltage (I-V)
and luminance-voltage (B-V) curves and luminescent
efficiency-current density curve of the device using complex 2 as
emitter with a doping level of 2%.
[0031] FIG. 8. Electroluminescent spectrum, current-voltage (I-V)
and luminance-voltage (B-V) curves and luminescent
efficiency-current density curve of the device using complex 2 as
emitter with a doping level of 4%.
[0032] FIG. 9. Electroluminescent spectrum, current-voltage (I-V)
and luminance-voltage (B-V) curves and luminescent
efficiency-current density curve of the device using complex 3 as
emitter with a doping level of 4%.
[0033] FIG. 10. Electroluminescent spectrum, current-voltage (I-V)
and luminance-voltage (B-V) curves and luminescent
efficiency-current density curve of the device using complex 16 as
emitter with a doping level of 4%.
DETAILED DESCRIPTION OF THE INVENTION
[0034] The present invention is generally directed to syntheses and
properties of a family of organometallic light-emitting materials
and their applications in high-performance OLEDs. These novel
complexes possess several chemical and structural characteristics
as follows:
[0035] Cyclometalated diimine complexes of Group 10 metals,
including platinum,
[0036] Neutral molecules,
[0037] Square planar coordination environment around metal,
[0038] Tridentate ligands defined as (C N N) occupy three of the
coordination sites, and
[0039] Acetylide (alkynyl) group occupies the fourth coordination
site.
[0040] The type of [(C N N)Pt(II)] complexes which combine the
structural and spectroscopic characteristics of both diimine and
cyclometalated PT(II) complexes have been reported ((a) Lai, S. W.;
et al. Inorg. Chem. 38, 4046 (1999). (b) Cheung, T. C.; et al. J.
Chem. Soc., Dalton Trans. 1645 (1996). (c) Lai, S. W.; et al.
Organometallics 18, 3327 (1999). (d) Yip, J. H. K.; et al. Inorg.
Chem. 39, 3537 (2000). (e) Neve, F.; et al. Inorg. Chem. 36, 6150
(1997)). The results demonstrated that these complexes are good
room-temperature phosphorescent emitters both in solid state and in
fluid solution. The relatively long-lived emissions occurring in
the range of .lamda..sub.max 530-800 nm have been assigned to
triplet metal-to-ligand charge transfer (.sup.3MLCT) or
metal-metal-to-ligand charge transfer (.sup.3MMLCT) excited
states.
[0041] The present invention will now be described in detail for
specific preferred embodiment of the invention, it being understood
that these embodiments are intended only as illustrative examples
and the invention is not to be limited thereto.
Syntheses of the Complexes
[0042] We have synthesized a number of the tridentate
cyclometalated Pt(II) arylacetylides ##STR4## with different
substituents on the aryl rings which are depicted in either Formula
I or II. The synthetic methods are shown in Scheme 1: ##STR5##
[0043] The tridentate (C N N) ligands were prepared according to
Krohnke's method (Krohnke, F. Synthesis 1 (1976)). The various
acetylenes were prepared with Sonogashira's method (Takahashi, S.
et al. Synthesis 627 (1980)). The Cl-ligated precursors [(C N
N)PtCl] were prepared under Constable's condition (Constable, E.
C.; et al. J. Chem. Soc., Dalton Trans. 2251 (1992) and 443
(1990)). The desired complexes were synthesized by Cu(I)-organic
amine-catalyzed reactions. For example, to a mixture of [(C N
N)PtCl] (0.33 mmol), terminal acetylene (1 mmol) and Et.sub.3N (3
mL) in degassed CH.sub.2Cl.sub.2 (30 mL) solution was added CuI (5
mg). The suspension was stirred for 12 h under a nitrogen
atmosphere at room temperature and in the absence of light. The
resultant mixture was rotatory-evaporated to dryness. The crude
product was purified by flash chromatography (neutral
Al.sub.2O.sub.3, CH.sub.2Cl.sub.2 as eluent) and/or
recrystallization from dichloromethane/diethyl ether. Examples are
listed in Table I but not limited by them: TABLE-US-00001 TABLE I
Complex Chemical Structure Characterization Data 1 ##STR6## orange
crystalline powder. FAB MS: 524 (M.sup.+ + H), 523 (M.sup.+);
.sup.1H NMR (300 MHz, CDCl.sub.3, 22.degree. C., TMS): .delta. =
9.02 (d, 1H, J =5.3 Hz), 7.94 (t, 1H, J = 7.8 Hz), 7.87 (d, 1H, J =
7.4 Hz), 7.82 (d, 1H, J = 8.0 Hz). 7.68 (t, 1H, J = 8.0 Hz), 7.51
(d, 1H, J = 7.7 Hz), 7.45 (t, 1H, J = 7.5 Hz), 7.41 (d, 1H, J = 8.1
Hz), 7.21 (d, 1H, # J = 7.2 Hz), 7.15 (t, 1H, J = 7.4 Hz), 7.02 (t,
1H, J = 7.5 Hz), 0.27 (s, 9H). 2 ##STR7## orange crystalline
powder. FAB MS: 528 (M.sup.+ + H), 527 (M.sup.+); .sup.1H NMR (300
MHz, CDCl.sub.3, 22.degree. C., TMS): .delta. = 9.15 (d, 1H, J =4.3
Hz), 7.97 (m, 2H), 7.85 (d, 1H, J = 8.1 Hz), 7.75 (t, 1H, J =8.0
Hz), 7.55 (m, 3H), 7.48 (m, 2H), 7.31 (m, 3H), 7.17 (t, 2H, J = 7.0
Hz), 7.05 (t, 1H, J = 7.4 Hz). 3 ##STR8## orange-red crystalline
powder. FAB MS: 542 (M.sup.+ + H), 541 (M.sup.+); .sup.1H NMR (300
MHz, CDCl.sub.3, 22.degree. C., TMS): .delta. = 9.07 (d, 1H, J =
4.3 Hz), 7.92 (m, 2H), 7.82 (d, 1H, J = 7.8 Hz), 7.69 (t, 1H, J =
8.0 Hz), 7.53 (d, 1H, J = 7.3 Hz), 7.43 (m, 4H), 7.27 (d, 1H, J =
6.3 Hz), 7.15 (t, 1H, J = 7.3 Hz), 7.10 (d, 2H, J = 7.9 Hz), 7.02
(t, 1H, # J = 7.5 Hz), 2.35 (s, 3H). 4 ##STR9## red crystalline
powder. FAB MS: 558 (M.sup.+ + H) 557 (M.sup.+); .sup.1H NMR (300
MHz, CDCl.sub.3, 22.degree. C., TMS): .delta. = 9.12 (d, 1H, J =
5.2 Hz), 7.95 (m, 2H), 7.83 (d, 1H, J = 7.9 Hz), 7.72 (t, 1H, J =
8.0 Hz), 7.50 (m, 3H), 7.49 (d, 2H, J = 8.8 Hz), 7.30 (d, 1H, J =
6.6 Hz), 7.16 (t, 1H, J = 7.4 Hz), 7.03 (t, 2H, J = 7.4 Hz), 6.84
(d, 2H, # J = 8.8 Hz), 3.82 (s, 3H). 5 ##STR10## orange-red
crystalline powder. FAB MS: 562 (M.sup.+); .sup.1H NMR (300 MHz,
CDCl.sub.3, 22.degree. C., TMS): .delta. = 9.05 (d, 1H, J = 5.1
Hz), 7.94 (t, 1H, J = 7.8 Hz), 7.87 (d, 1H, J = 7.5 Hz), 7.81 (d,
1H, J = 7.9 Hz), 7.71 (t, 1H, J = 8.0 Hz), 7.52 (d, 1H, J = 7.7
Hz), 7.46 (m, 2H), 7.45 (d, 1H, J = 8.5 Hz), 7.27 (d, 1H, J = 4.2
Hz), 7.23 (d, 2H, J = 8.8 Hz), # 7.15 (t, 1H, J = 7.4 Hz), 7.03 (t,
1H, J = 7.4 Hz). 6 ##STR11## black-red crystals. FAB MS: 546
(M.sup.+ + H), 545 (M.sup.+); .sup.1H NMR (300 MHz, CDCl.sub.3,
22.degree. C., TMS): .delta. = 9.12 (d, 1H, J = 5.2 Hz), 7.97 (t,
1H, J = 7.9 Hz), 7.92 (d, 1H, J = 7.6 Hz), 7.84 (d, 1H, J = 8.0
Hz), 7.74 (t, 1H, J = 8.0 Hz), 7.56-7.47 (m, 5H), 7.32 (d, 1H, J =
7.6 Hz), 7.17 (t, 1H, J = 7.4 Hz), 7.05 (t, 1H, J = 7.5 Hz), 6.98
(pseudo-t, # 2H, J = 7.7 Hz). 7 ##STR12## orange crystalline
powder. FAB MS: 573 (M.sup.+ + H), 572 (M.sup.+); .sup.1H NMR (300
MHz, d.sub.6-DMSO, 22.degree. C., TMS): .delta. = 8.98 (d, 1H, J =
4.5 Hz), 8.48 (d, 1H, J = 8.0 Hz), 8.32 (t, 1H, J = 8.0 Hz), 8.20
(d, 1H, J = 7.4 Hz), 8.14 (d, 2H, J = 8.8 Hz), 8.11 (t, 1H, J = 8.0
Hz), 7.99 (d, 1H, J = 7.8 Hz), 7.83 (t, 1H, J = 75 Hz), 7.68 (d,
1H, J = 7.3 Hz), # 7.62 (d, 1H, J = 7.4 Hz), 7.58 (d, 2H, J = 8.9
Hz), 7.11 (t, 1H, J = 7.3 Hz), 7.05 (t, 1H, J = 7.3 Hz). 8
##STR13## brown crystals. FAB MS: 534 (M.sup.+ + H), 533 (M.sup.+);
.sup.1H NMR (300 MHz, d.sub.6-DMSO, 22.degree. C., TMS): .delta. =
8.94 (d, 1H, J = 5.1 Hz), 8.46 (d, 1H, J = 7.9 Hz), 8.30 (t, 1H, J
= 7.8 Hz), 8.17 (d, 1H, J = 7.6 Hz), 8.08 (t, 2H, J = 7.9 Hz), 7.96
(d, 1H, J = 7.9 Hz), 7.84 (t, 1H, J = 6.4 Hz), 7.66 (d, 1H, J = 6.2
Hz), 7.59 (d, 1H, J = 7.4 Hz), 7.21 # (d, 1H, J = 4.9 Hz), 7.10 (t,
1H, J = 7.3 Hz), 7.03 (t, 1H, J = 7.3 Hz), 6.97-6.92 (m, 2H). 9
##STR14## orange crystalline powder. FAB MS: 604 (M.sup.+ + H), 603
(M.sup.+); .sup.1H NMR (300 MHz, d.sub.6-DMSO, 22.degree. C., TMS):
.delta. = 8.99 (d, 1H, J = 4.8 Hz), 8.68 (d, 1H, J = 8.0 Hz), 8.50
(s, 1H), 8.32 (t, 1H, J = 7.7 Hz), 8.24 (s, 1H), 8.08-8.05 (m, 2H),
7.84-7.78 (m, 2H), 7.70 (d, 1H, J = 7.9 Hz), 7.61-7.55 (m, 3H),
7.36 (d, 1H, J =7.2 Hz), 7.26 (t, 1H, J = 7.6 Hz), # 7.17-7.01 (m,
3H). 10 ##STR15## orange crystalline powder. FAB MS: 614 (M.sup.+ +
H), 613 (M.sup.+); .sup.1H NMR (300 MHz, CDCl.sub.3, 22.degree. C.,
TMS): .delta. = 8.90 (d, 1H, J =5.4 Hz), 7.99 (t, 1H, J = 7.5 Hz),
7.90 (d, 1H, J = 8.0 Hz), 7.76 (d, 1H, J = 6.2 Hz), 7.60-7.57 (m,
3H), 7.40-7.31 (m, 4H), 7.26 (d, 1H, J = 6.1 Hz), 7.03-6.98 (m,
2H), 2.48 (s, 3H), 0.33 (s, 9H). 11 ##STR16## orange crystalline
powder. FAB MS: 618 (M.sup.+ + H), 617 (M.sup.+); .sup.1H NMR (300
MHz, d.sub.6-DMSO, 22.degree. C., TMS): .delta. = 9.04 (d, 1H, J =
5.0 Hz), 8.69 (d, 1H, J = 7.9 Hz), 8.50 (s, 1H), 8.34 (t, 1H, J =
7.7 Hz), 8.24 (s, 1H), 8.01 (d, 2H, J = 7.5 Hz), 7.84-7.74 (m, 3H),
7.40-7.30 (m, 4H), 7.30 (t, 2H, J = 7.5 Hz), 7.18-7.06 (m, 3H),
2.40 (s, 3H). 12 ##STR17## red crystals. FAB MS: 632 (M.sup.+ + H),
631 (M.sup.+); .sup.1H NMR (300 MHz, d.sub.6-DMSO, 22.degree. C.,
TMS): .delta. = 9.05 (d, 1H, J = 4.9 Hz), 8.56 (d, 1H, J = 8.0 Hz),
8.34 (s, 1H), 8.20 (t, 1H, J = 7.9 Hz), 8.00 (s, 1H), 7.85 (d, 2H,
J = 8.1 Hz), 7.76-7.68 (m, 2H), 7.62 (d, 1H, J = 8.2 Hz), 7.31 (d,
2H, J = 8.1 Hz), 7.25 (d, 2H, J =8.0 Hz), # 7.07-6.97 (m, 4H), 2.39
(s, 3H), 2.28 (s, 3M). 13 ##STR18## orange crystalline powder. FAB
MS: 634 (M.sup.+ + H), 633 (M.sup.+); .sup.1H NMR (300 MHz,
d.sub.6-DMSO, 22.degree. C., TMS): .delta. = 9.00 (d, 1H, J = 4.9
Hz), 8.69 (d, 1H, J = 8.1 Hz), 8.48 (s, 1H), 8.32 (t, 1H, J = 7.9
Hz), 8.26 (s, 1H), 8.08 (d, 2H, J = 8.8 Hz), 8.06-7.81 (m, 2H),
7.72 (d, 1H, H = 7.1 Hz), 7.35 (d, 2H, J = 7.1 Hz), 7.26 (t, 2H, J
= 7.6 Hz), # 7.16-7.04 (m, 5H), 3.84 (s, 3H). 14 ##STR19## brown
crystalline powder. FAB MS: 638 (M.sup.+); .sup.1H NMR (300 MHz,
d.sub.6-DMSO, 22.degree. C., TMS): .delta. = 8.99 (broad, 1H), 8.64
(d, 1H, J = 7.7 Hz), 8.47 (s, 1H), 8.31 (t, 1H, J = 7.6 Hz), 8.21
(s, 1H), 8.09 (d, 2H, J = 8.1 Hz), 7.82-7.68 (m, 3M), 7.62 (d, 2H,
J = 8.2 Hz), 7.38 (d, 2H, J = 7.2 Hz), 7.28 (t, 2H, J = 7.3 Hz),
7.18 (t, 1H, J = 7.0 Hz), 7.08-7.03 (m, 2H). 15 ##STR20## brown
needles. FAB MS: 534 (M.sup.+ + H), 533 (M.sup.+); .sup.1H NMR (300
MHz, d.sub.6-DMSO, 22.degree. C., TMS): .delta. = 9.01 (d, 1H, J =
5.0 Hz), 8.46 (d, 1H, J = 8.2 Hz), 8.35 (t, 1H, J = 7.9 Hz), 8.02
(d, 1H, J = 7.6 Hz), 7.96 (t, 1H, J = 7.8 Hz), 7.85 (t, 1H, J = 6.4
Hz), 7.72 (d, 1H, J = 4.9 Hz), 7.56 (d, 1H, J = 7.3 Hz), 7.38 (d,
2H, J = 7.0 Hz), # 7.29 (t, 2H, J = 7.6 Hz), 7.17 (t, 1H, J = 7.3
Hz), 7.11 (d, 1H, J = 4.6 Hz). 16 ##STR21## brown needles. FAB MS:
548 (M.sup.+ + H), 547 (M.sup.+); .sup.1H NMR (300 MHz,
d.sub.6-DMSO, 22.degree. C., TMS): .delta. = 9.03 (d, 1H, J = 5.2
Hz), 8.47 (d, 1H, J = 8.2 Hz), 8.34 (t, 1H, J = 7.2 Hz), 8.02 (d,
1H, J = 7.9 Hz), 7.96 (t, 1H, J = 7.7 Hz), 7.86 (t, 1H, J = 6.3
Hz), 7.73 (d, 1H, J = 4.9 Hz), 7.56 (d, 1H, J = 7.6 Hz), 7.26 (d,
2H, J = 7.9 Hz), # 7.13 (d, 1H, J = 4.6 Hz), 7.11 (d, 2H, J = 7.9
Hz), 2.30 (s, 3M).
Thermal-Stability of the Complexes
[0044] Ideally, a low molecular weight component to be used in
OLEDs should be sublimable and stable at standard deposition
conditions. Importantly, many of the complexes in the present
invention are thermally stable up to .about.400.degree. C. and
decompose to give metallic platinum only at temperature above
420.degree. C. (see TGA curves for complexes 2 and 15 in FIGS. 2
and 3 respectively).
[0045] The observed thermal stability of these complexes described
in the present invention which contain a tridentate cyclometalating
ligand, contrasts sharply with the bidentate Pt(thpy).sub.2 emitter
described by Lamasky et al. which are unstable upon
sublimation.
Spectroscopic Properties of the Complexes
[0046] In present invention, the ligation of an acetylide group to
the (C N N)Pt(II) moiety neutralizes the positive charge centered
on Pt(II), enhances the stability of these complexes, and moreover,
shifts the .sup.3MLCT emission bathochromically. The family of
complexes depicted by Formula I and II display strong orange to red
photoluminescence in fluid solution. Examples of characteristic
absorption and emission band of these emitters in present invention
are summarized in Table II: TABLE-US-00002 TABLE II Complex
Emission (see Absorption .lamda..sub.max/nm Table I) MLCT Band/nm
(.epsilon./mol dm.sup.-1 cm.sup.-1) (.tau..sub.0/.mu.s;
.phi..sub.0) 1 427 (5490), 450 (sh, 4920), 505 (sh, 430) 570 (0.31;
0.041) 2 434 (5180), 455 (4940), 510 (sh, 470) 582 (0.39; 0.037) 3
440 (5090), 465 (sh, 4950), 515 (sh, 1190) 600 (0.17; 0.019) 4 440
(4200), 460 (sh, 4220), 520 (sh, 1570) 630 5 432 (8670), 455 (sh,
8310), 515 (sh, 720) 598 (0.53; 0.076) 6 433 (4880), 453 (sh,
4760), 515 (sh, 640) 585 (0.33; 0.033) 7 415 (sh, 12930), 510 (sh,
540) 560 (0.93; 0.077) 15 436 (4970), 460 (sh, 4490), 515 (sh, 460)
615 (1.02; 0.029), 660 (sh) 16 442 (5010), 465 (sh, 4800), 520 (sh,
670) 616 (0.91; 0.025), 660 (sh)
Notice that all the data were collected with degassed
CH.sub.2Cl.sub.2 solution at 298 K. Exemplified absorption and
emission spectra for complexes 2 and 15 are shown in FIGS. 4 and 5
respectively. The intense orange to red phosphorescence of the
complexes in the present invention together with their stability
towards sublimation means that these materials can be used as
emitters or dopants in high-performance OLEDs. Organic
Light-Emitting Devices
[0047] The devices using the complexes in present invention, as
fabricated by Prof. S. T. Lee of City University of Hong Kong,
possess the multi-layer heterostructure shown in FIG. 6.
[0048] All the organic layers including the Pt complexes described
above and cathodes were vacuum-deposited onto the ITO subtrate. NPB
(N,N'-di-1-naphthyl-N,N'-diphenyl-benzidine) and Alq.sub.3
(q=8-hydroxyquinolinyl) were used as the hole transporting and
electron transporting layer, respectively. BCP
(2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline, bathocuproine) was
used to confine excitons within the luminescent zone. Magnesium
silver alloy was applied as the cathode. The selected Pt complex
was doped into the conductive host material CBP
(4,4'-N,N'-dicarbazole-biphenyl) as phosphorescent emitter. The
optimal doping levels were adjusted at 2,4 and 6% and
electroluminescence from the Pt complexes were observed.
EXAMPLES
[0049] A number of examples are listed below to further illustrate
the invention
Example 1
[0050] Complex 2 was used as the emitter. Typical
electroluminescent spectrum, current-voltage (I-V) and
luminance-voltage (B-V) curves and luminescent efficiency-current
density curve of the device with a doping level of 2% are shown in
FIG. 7. Turn-on voltage: .about.5 V; maximum luminance: 9600
Cd/m.sup.2 at 12 V; maximum efficiency: 4.2 Cd/A at 25 mA/cm.sup.2.
In the electroluminescent spectrum, a peak at 430 nm besides the
band at 560-630 nm is observed, indicating insufficient energy
transfer between the host and the dopant.
Example 2
[0051] The performance of the device using complex 2 as emitter
with a doping level of 4% are shown in FIG. 8. Turn-on voltage:
.about.5 V; maximum luminance: 7900 Cd/m.sup.2 at 10 V; maximum
efficiency: 2.4 Cd/A at 30 mA/cm.sup.2. At this doping level,
energy transfer between the host and the dopant is saturated, thus
emission from the host is avoided.
Example 3
[0052] Complex 3 was used as the emitter. The performance of the
device with a doping level of 4% are shown in FIG. 9. A
bathochromic electroluminescence is observed (.lamda..sub.max 580
nm), which is coinciding with the trend of the photoluminescence
shown by these complexes in room-temperature CH.sub.2Cl.sub.2
solutions. Turn-on voltage: .about.5 V; maximum luminance: 4000
Cd/m.sup.2 at 12 V; maximum efficiency: 1.4 Cd/A at 20
mA/cm.sup.2.
Example 4
[0053] Complex 16 was used as the emitter. The performance of the
device with a doping level of 4% are shown in FIG. 10. The
electroluminescence is red with vibronically structured emission
spectrum (.lamda..sub.max 610 nm, 660 nm). Turn-on voltage:
.about.5 V; maximum luminance: 3200 Cd/m.sup.2 at 13 V; maximum
efficiency: 1.0 Cd/A at 30 mA/cm.sup.2.
[0054] Generally, the organometallic light-emitting materials as
depicted in Figure I and II in present invention are demonstrated
to be novel electrophosphorescent emitters applicable to
high-efficiency and -brightness orange to red light OLEDs.
[0055] While it is apparent that the embodiments of the invention
herein disclosed are well suited to fulfill the objectives stated
above, it will be appreciated that numerous modifications and other
embodiments may be implemented by those skilled in the art, and it
is intended that the appended claims cover all such modifications
and embodiments that fall within the true spirit and scope of the
present invention.
[0056] A number of references have been cited and the entire
disclosures of which are incorporated herein by reference.
* * * * *
References