U.S. patent application number 12/297010 was filed with the patent office on 2009-08-20 for biphenyl-metal complexes-monomeric and oligomeric triplet emitters for oled applications.
This patent application is currently assigned to UNIVERSITAET REGENBURG. Invention is credited to Rafal Czerwieniec, Uwe Monkowius, Hartmut Yersin.
Application Number | 20090206735 12/297010 |
Document ID | / |
Family ID | 38161916 |
Filed Date | 2009-08-20 |
United States Patent
Application |
20090206735 |
Kind Code |
A1 |
Yersin; Hartmut ; et
al. |
August 20, 2009 |
BIPHENYL-METAL COMPLEXES-MONOMERIC AND OLIGOMERIC TRIPLET EMITTERS
FOR OLED APPLICATIONS
Abstract
The present invention relates to light-emitting devices and
novel emitter materials as well as emitter systems and, in
particular, organic light-emitting devices (OLEDs). In particular,
the invention relates to the use of luminescent complexes as
emitters in such devices.
Inventors: |
Yersin; Hartmut; (Sinzing,
DE) ; Monkowius; Uwe; (Regensburg, DE) ;
Czerwieniec; Rafal; (Regensburg, DE) |
Correspondence
Address: |
CONNOLLY BOVE LODGE & HUTZ, LLP
P O BOX 2207
WILMINGTON
DE
19899
US
|
Assignee: |
UNIVERSITAET REGENBURG
Regensburg
DE
|
Family ID: |
38161916 |
Appl. No.: |
12/297010 |
Filed: |
April 12, 2007 |
PCT Filed: |
April 12, 2007 |
PCT NO: |
PCT/EP2007/003261 |
371 Date: |
January 22, 2009 |
Current U.S.
Class: |
313/504 ; 445/58;
556/136 |
Current CPC
Class: |
Y10S 428/917 20130101;
H01L 51/0084 20130101; H01L 51/0035 20130101; H01L 51/004 20130101;
H01L 51/0085 20130101; H01L 51/0043 20130101; H01L 51/5016
20130101; H01L 51/0087 20130101 |
Class at
Publication: |
313/504 ; 445/58;
556/136 |
International
Class: |
H01J 1/62 20060101
H01J001/62; H01J 9/00 20060101 H01J009/00; C07F 15/00 20060101
C07F015/00 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 13, 2006 |
DE |
10 2006 017 485.2 |
Claims
1-74. (canceled)
75. An oligomer comprising at least one complex of the formula (I)
(s-bph)ML (I) in which M represents Pt(II), Rh(I), Ir(I), Pd(II) or
Au(III), L represents a bidentate ligand or L=X.sub.2, where each
X, independently, represents a monodentate ligand, and wherein
optionally L or optionally at least one X or optionally both L and
at least one X contain a polymerizable group, s-bph represents a
ligand which has an Ar--Ar group, where Ar represents an aromatic
ring system.
76. A light-emitting device comprising (i) an anode, (ii) a cathode
and (iii) an emitter layer arranged between and in direct or
indirect contact with the anode and the cathode, comprising at
least one of the oligomer according to claim 75 used as an
emitter.
77. The light-emitting device according to claim 76, wherein the
proportion of complexes of the formula (I) in the emitter layer is
greater than 10% by weight, based on the total weight of the
emitter layer and L represents a bidentate ligand or L=X.sub.2,
where each X, independently, represents a monodentate ligand.
78. The light-emitting device according to claim 77, wherein the
proportion of complexes of the formula (I) in the emitter layer is
greater than 80% by weight based on the total weight of the emitter
layer.
79. The light-emitting device according to claim 77, wherein the
proportion of complexes of the formula (I) in the emitter layer is
greater than 95% by weight based on the total weight of the emitter
layer.
80. The light-emitting device according to claim 77, wherein
L=X.sub.2, where each X is selected, independently, from CO, CNR,
NCR, RN.dbd.CR', SCNR, NCSR, NCOR, CN, SCN.sup.-, OCN.sup.-,
F.sup.-, Cl.sup.-, Br.sup.-, I.sup.-, .sup.-CH.dbd.CRR',
.sup.-C.ident.CR, alkyl, aryl, heteroaryl groups, .sup.-OR,
.sup.-SR, .sup.-SeR, .sup.-NR.sub.2, .sup.-PR.sub.2,
.sup.-SiR.sub.3, where R and R' each, independently of one another,
represent H, alkyl, aryl, heteroaryl, alkenyl, alkynyl, halogen,
--NR''.sub.2, --PR''.sub.2, --OR'' or --SR'', where R'' represents
H, alkyl, aryl, heteroaryl, alkenyl or alkynyl, where R and R' may
also be linked to one another.
81. The light-emitting device according to claim 77, wherein the
emitter comprises the compound (bph)Pt(CO).sub.2,
(d.sup.tBubph)Pt(CO).sub.2 or (tmbph)Pt(CO).sub.2.
82. The light-emitting device according to claim 77, wherein L
represents a bidentate ligand selected from CN--B--NC.sub.2
NC--B--CN, diimines, acetylacetonate,
[RN--CR'.dbd.CH--CR'.dbd.NR].sup.-, [pz.sub.2BH.sub.2].sup.-
(pz=pyrazolyl), [O--B--O].sup.2-, [S--B--S].sup.2-,
[Se--B--Se].sup.2-, [RN--B--NR].sup.2-, 2,2'-biphenylene,
[CH.dbd.CR--B--CR.dbd.CH].sup.2- or
[C.ident.C--B--C.ident.C].sup.2-, where B is a bridging group,
which is an alkylene or arylene group, which is optionally
substituted or optionally contains at least one heteroatom.
83. The light-emitting device according to claim 77, wherein
complexes of the formula (I) are present in the emitter layer in a
columnar structure.
84. The light-emitting device according to claim 77, wherein at
least two different complexes of the formula (I) are present in the
columnar structure.
85. The light-emitting device according to claim 77, wherein the
complex of the formula (I) in the emitter layer is bonded to a
polymer.
86. The light-emitting device according to claim 85, wherein the
bonding to the polymer takes place via polymerizable groups of the
ligands L.
87. The light-emitting device according to claim 86, wherein the
complex of the formula (I) (s-bph)ML is formed from a complex of
the formula (III) (s-bph)ML.sup.1 (III), in which L' represents a
bidentate ligand which has a polymerizable group.
88. The light-emitting device according to claim 87, wherein
L.sup.1 has the formula ##STR00019## in which R represents alkyl,
aryl, alkoxy, phenoxy, alkylamine or arylamine.
89. The light-emitting device according claim 87, wherein monomers
of the formula (III) are applied and subsequently polymerized.
90. The light-emitting device according to claim 76, wherein M in
formula (I) represents Pt(II).
91. The light-emitting device according to claim 76, which further
comprises a hole-conductor layer or/and an electron-conductor
layer.
92. The light-emitting device according to claim 76, which further
comprises a CsF or LiF interlayer.
93. The light-emitting device according to claim 76, wherein the
device is arranged on a substrate.
94. The light-emitting device according to claim 76, wherein the
device is arranged on a glass substrate.
95. The light-emitting device according to claim 76, wherein the
complex present in the emitter layer is a triplet emitter.
96. The light-emitting device according to claim 95, wherein the
emitter layer comprises complexes of the formula (I) in a
concentration of 1 to 10% by weight, based on the total weight of
the emitter layer.
97. The light-emitting device according to claim 76, wherein s-bph
represents the formula (II) ##STR00020## wherein R.sup.1 to R.sup.8
each, independently of one another, represent H, alkyl, aryl,
heteroaryl, alkenyl, alkynyl, halogen, --NR.sub.2, --PR.sub.2, --OR
or --SR, wherein R is H, alkyl, aryl, heteroaryl, alkenyl or
alkynyl, wherein the radicals R.sup.1 to R.sup.8 may also be linked
to one another, and * represent the coordination sites of the
ligand.
98. A triplet emitter which comprises the oligomer according to
claim 75.
99. A process for the production of a light-emitting device
according to claim 76, which comprises introducing at least one
complex of the formula (I) as oligomer emitter in the emitter layer
by means of vacuum sublimation.
100. A process for the production of a light-emitting device
according to claim 76, which comprises introducing at least one
complex of the formula (I) as oligomer emitter in the emitter layer
by a wet-chemical method.
101. The oligomer according to claim 75, which comprises at least
two complexes of the formula (I).
102. The oligomer according to claim 101, which comprises at least
10 complexes of the formula (I).
103. The oligomer according to claim 101, wherein the at least two
complexes are arranged as a stack.
104. The oligomer according to claim 101, wherein the oligomer has
a columnar structure.
105. The oligomer according to claim 101, wherein the oligomer
comprises complexes of the formula (s-bph)ML*, in which M
represents Pt(II), Rh(I), Ir(I), Pd(II) or Au(III), s-bph
represents a ligand which has an Ar--Ar group, where Ar represents
an aromatic ring system and L* represents a non-bulky ligand.
106. The oligomer according to claim 105, wherein the oligomer has
the structural element [(s-bph)ML*].sup.n+[(s'-bph)M'L*'].sup.m-,
where M and M' each, independently, represent Pt(II), Rh(I), Ir(I),
Pd(II) or Au(III), L* and L' each, independently, represent a
bidentate ligand or two monodentate ligands, s-bph and s'-bph each
have an Ar--Ar group, where Ar represents an aromatic ring system,
and n and m each represent an integer from 0 to 5, where at least
one group M', L*', s'-bph has been modified to give the groups M,
L* and s-bph.
107. The oligomer according to claim 106, wherein the M-M
separation between two adjacent complexes in the stack is
.ltoreq.0.37 nm.
108. The oligomer according to claim 75 which are further bonded to
polymers, and metal-metal interactions form.
109. The oligomer according to claim 108, wherein the metal-metal
interactions result in an emission.
110. A crystalline layer comprising the oligomer according to claim
101.
111. The crystalline layer according to claim 110 which has a
charge-carrier mobility of .gtoreq.10.sup.-3 cm.sup.2/Vs.
112. Segments of the oligomer according to claim 75 in a common
matrix material which are used for emission layers (EMLs) in OLEDs,
for increasing the charge-carrier mobilities.
113. A complex of the formula A, B or C ##STR00021## wherein the
atoms A.sup.1-A.sup.8 are each selected, independently, from C, N,
O and S, and the ligands R.sup.1-R.sup.8 each, independently,
represent H, CH.sub.3, C.sub.2H.sub.5, CH(CH.sub.3).sub.2,
C(CH.sub.3).sub.3, CF.sub.3, C.sub.nH.sub.2n+1, F, CN, OCH.sub.3,
OC.sub.nH.sub.2n+1, SCH.sub.3, SC.sub.nH.sub.2n+1,
N(CH.sub.3).sub.2, N(C.sub.nH.sub.2n+1)(C.sub.nH.sub.2n+1), where
n=1 to 20, where two or more of the radicals R.sup.1 to R.sup.8 may
optionally be linked to one another and thus form additional
aliphatic, aromatic or heteroaromatic rings, and the ligands L' and
L.sup.2 each, independently, represent CO, NC--CH.sub.3,
NC--CH(CH.sub.3).sub.2, NC--C.sub.nH.sub.2n+1, CN--CH.sub.3,
CN--CH(CH.sub.3).sub.2, CN--C(CH.sub.3).sub.3,
NC--C.sub.nH.sub.2n+1, P(CH.sub.3).sub.3, As(CH.sub.3).sub.3,
N(CH.sub.3).sub.2, where the ligands L.sup.1 and L.sup.2 may
optionally be parts of a chelate ligand.
114. The complex according to claim 113 which has one of the
following formulas ##STR00022##
115. The complex according to claim 113 which has one of the
following formulas ##STR00023##
116. The complex according to claim 113 which has one of the
following formulas ##STR00024## where the atoms A.sup.1-A.sup.8 are
each selected, independently, from C, N, O, S, the ligands
R.sup.1-R.sup.8 each, independently, represent H, CH.sub.3,
C.sub.2Hs, CH(CH.sub.3).sub.2, C(CH.sub.3).sub.3, CF.sub.3,
C.sub.nH.sub.2n+1, F, CN, OCH.sub.3, OC.sub.nH.sub.2n+1, SCH.sub.3,
SC.sub.nH.sub.2n+1, N(CH.sub.3).sub.2,
N(C.sub.nH.sub.2n+1)(C.sub.nH.sub.2n+1), where n=1 to 20, where two
or more of the radicals R.sup.1 to R.sup.8 may be linked to one
another and thus form additional aliphatic, aromatic or
heteroaromatic rings, and L.sup.1.andgate.L.sup.2 represents
diphosphine, diamine, diarsine or diene.
117. The oligomer according to claim 75, wherein L or at least one
X has a C.dbd.C group.
118. The oligomer according to claim 75, wherein L represents
##STR00025## in which each R, independently, represents H, an
alkyl, aryl, alkoxy, aryloxy, alkylamine or arylamine group.
119. The light-emitting device according to one of claim 76,
wherein L represents a bidentate ligand selected from diphosphines,
diamines, diarsines and dienes.
120. The light-emitting device according to claim 76, wherein L
represents a diphosphine selected from ##STR00026## ##STR00027##
wherein R represents alkyl, aryl, alkoxy, phenoxy, alkylamine or
arylamine.
121. The light-emitting device according to claim 76, wherein M is
Pt(II).
122. A complex which comprises the oligomer of claim 75, wherein L
represents a bidentate ligand or L=X.sub.2, where each X,
independently, represents a monodentate ligand, where L or at least
one X contains a polymerizable group.
123. The complex according to claim 122, wherein L or at least one
X has a C.dbd.C group.
124. The complex according to claim 122, wherein L represents
##STR00028## in which each R, independently, represents H, an
alkyl, aryl, alkoxy, aryloxy, alkylamine or arylamine group.
125. The complex according to claim 116, wherein
L.sup.1.andgate.L.sup.2 is a linear or cyclic diene having 6 to 10
C atoms or a diphosphine selected from ##STR00029## ##STR00030##
where R represents alkyl, aryl, alkoxy, phenoxy, alkylamine or
arylamine.
126. The complex according to claim 116, wherein
L.sup.1.andgate.L.sup.2 represents
Ph.sub.2P--CH.sub.2--CH.sub.2--PPh.sub.2 or cyclooctadiene.
127. The complex according to 116, which wherein the complex is
(biphenyl)(cyclooctadiene)platinum, (bph)Pt(COD), or
(biphenyl)(bis(diphenylphosphino)ethane)platinum, (bph)Pt(dppe)
##STR00031##
128. The complex according to claim 116, wherein in the complex is
one complex selected from the following group ##STR00032##
##STR00033##
Description
[0001] The present invention relates to light-emitting devices and,
in particular, organic light-emitting devices (OLEDs). In
particular, the invention relates to the use of luminescent
biphenyl-metal complexes as monomer and oligomer emitters in such
devices.
[0002] OLEDs (organic light-emitting devices or organic
light-emitting diodes) represent a novel technology which will
dramatically change display-screen and illumination technology.
OLEDs predominantly consist of organic layers, which are also
flexible and inexpensive to manufacture. OLED components can have a
large-area design as illumination elements, but also a small design
as pixels for displays.
[0003] A review of the function of OLEDs is given, for example, in
H. Yersin, Top. Curr. Chem. 2004, 241, 1.
[0004] Since the first reports on OLEDs (see, for example, Tang et
al., Appl. Phys. Lett. 51 (1987) 913), these devices have been
developed further, in particular with respect to the emitter
materials employed, where, in particular, so-called triplet or
phosphorescent emitters are of interest.
[0005] Compared with conventional technologies, such as, for
example, liquid-crystal displays (LCDs), plasma displays or
cathode-ray tubes (CRTs), OLEDs have numerous advantages, such as,
for example, a low operating voltage, a thin structure, pixels
which self-illuminate with high efficiency, high contrast and good
resolution as well as the possibility to display all colours.
Furthermore, an OLED emits light on application of an electrical
voltage instead of only modulating it. Whereas numerous
applications have already been developed for OLEDs and novel areas
of application have also been opened up, there is still a demand
for improved OLEDs and in particular for improved triplet emitter
materials. In the solutions to date, problems arise, in particular,
with the long-term stability, the thermal stability and the
chemical stability to water and oxygen. Furthermore, many emitters
exhibit only low sublimation ability. Furthermore, important
emission colours are frequently unavailable with emitter materials
known to date. High efficiencies frequently also cannot be achieved
at high current densities or high luminous densities. Finally,
problems exist with respect to manufacturing reproducibility in the
case of many emitter materials.
[0006] WO 03/087258 describes OLEDs comprising organometallic
compounds which are, in particular, pentacoordinated complexes with
16 valence electrons or hexacoordinated complexes with 18 valence
electrons. Likewise, EP 1 191 614 A2, US2002/0034656 A1 and WO
00/57676 A1 describe platinum compounds which contain both a
biphenyl group and also a bipyridine group as ligands.
[0007] It was an object of the present invention to provide novel
emitter materials, in particular for OLEDs and novel light-emitting
devices, which overcome at least some of the disadvantages of the
prior art and which have, in particular, high chemical
stability.
[0008] This object is achieved in accordance with the invention by
a light-emitting device comprising (i) an anode, (ii) a cathode and
(iii) an emitter layer arranged between and in direct or indirect
contact with the anode and the cathode, comprising at least one
complex of the formula (I)
(s-bph)ML,
in which M represents Pt(II), Rh(I), Ir(I), Pd(II) or Au(III), in
particular Pt(II), L represents a bidentate ligand or L=X.sub.2,
where each X, independently, represents a monodentate ligand, and
s-bph represents a ligand which has an Ar--Ar group, where Ar
represents an aromatic ring system, for example, in particular,
biphenyl or substituted biphenyl.
[0009] Surprisingly, it has been found that the use according to
the invention of the complexes of the formula (I) in the emitter
layer enables light-emitting devices which have excellent
properties to be obtained. In particular, the compounds employed in
accordance with the invention exhibit high quantum yields. In
addition, the complexes can be varied by substitution or/and
changing of the ligands, giving rise to a wide variety of
possibilities for modification or control of the emission
properties. In addition, a suitable choice of the ligands enables
compounds having high sublimation ability to be obtained.
[0010] The way in which an embodiment of the light-emitting devices
according to the invention functions is shown diagrammatically in
FIG. 1. The device comprises at least an anode, a cathode and an
emitter layer. One or both of the electrodes used as cathode or
anode advantageously has a transparent design, enabling the light
to be emitted through this electrode. The transparent electrode
material used is preferably indium tin oxide (ITO). A transparent
anode is particularly preferably employed. The other electrode can
likewise be made of a transparent material, but may also be formed
from another material having a suitable electron work function if
light is only to be emitted through one of the two electrodes. The
second electrode, in particular the cathode, preferably consists of
a metal of high electrical conductivity, for example aluminium or
silver, or an Mg/Ag or Ca/Ag alloy. An emitter layer is arranged
between the two electrodes. This can be in direct contact or
indirect contact with the anode and cathode, where indirect contact
means that further layers are present between the cathode or anode
and the emitter layer, so that the emitter layer and the anode
or/and cathode do not touch one another, but instead are in
electrical contact with one another via further interlayers. On
application of a voltage, for example a voltage of 2-20 V, in
particular 5-10 V, negatively charged electrons are emitted from
the cathode, for example a conductive metal layer, particularly
preferably from an aluminium cathode, and migrate in the direction
of the positive anode. Positive charge carriers, so-called holes,
in turn migrate from this anode in the direction of the cathode. In
accordance with the invention, the emitter layer arranged between
the cathode and anode comprises organometallic complexes of the
formula (I) as emitter molecules. The migrating charge carriers,
i.e. a negatively charged electron and a positively charged hole,
recombine at the emitter molecules or in their vicinity and result
in neutral, but energetically excited states of the emitter
molecules. The excited states of the emitter molecules then release
the energy as light emission.
[0011] The light-emitting devices according to the invention can be
produced by vacuum deposition so long as the emitter materials are
sublimable. Alternatively, construction via wet-chemical
application is also possible, for example via spin-coating methods,
via ink-jet printing or via screen-printing methods. The structure
of OLED devices is described in detail, for example, in
US2005/0260449 A1 and in WO 2005/098988 A1.
[0012] The light-emitting devices according to the invention can be
manufactured by means of the vacuum sublimation technique and
comprise a plurality of further layers, in particular an
electron-injection layer and an electron-conduction layer (for
example Alq.sub.3=Al 8-hydroxyquinoline or .beta.-Alq=Al
bis(2-methyl-8-hydroxyquinolato)-4-phenylphenolate) and/or a
hole-injection (for example CuPc) and hole-conduction layer or
hole-conduction layer (for example .alpha.-NPD). However, it is
also possible for the emitter layer to take on functions of the
hole- or electron-conduction layer.
[0013] The emitter layer preferably consists of an organic matrix
material having a sufficiently large singlet S.sub.0--triplet TX
energy gap (UGH matrix material), for example comprising UGH, PVK
(polyvinylcarbazole), CBP (4,4'-bis(9-carbazolyl)biphenyl) or other
matrix materials. The emitter complex is doped into this matrix
material, for example preferably to the extent of 1 to 10 percent
by weight. The HOMO and LUMO energy values, which are important for
the selection of matrix materials in OLED devices, of some selected
biphenyl-Pt(II) complexes are shown in Table 2.
TABLE-US-00001 TABLE 2 Electrochemical data of some selected
biphenyl-Pt(II) complexes Ligand E.sub.red [V] E.sub.ox [V]
HOMO.sup.d [eV] LUMO.sup.d [eV] CO -1.08.sup.a,b 1.1.sup.a,b -5.9
-3.7 Et.sub.2S -1.14.sup.c 1.35.sup.a,c -6.0 -3.7 py -1.85.sup.c
0.81.sup.a,c -5.5 -3.1 MeCN -1.67.sup.c 0.85.sup.a,c -5.5 -3.3 en
-1.71.sup.c 0.67.sup.a,c -5.3 -3.2 bpy -1.47.sup.c 0.07.sup.a,c
-4.7 -3.5 .sup.airreversible, .sup.bferrocene/ferrocenium,
.sup.cSCE = standard calomel electrode, .sup.dagainst vacuum
[0014] Suitable matrix materials can be selected on the basis of
these values and the emissions. The emitter layer can also be
achieved without a matrix by applying the corresponding complex as
100% material. A corresponding embodiment is described below.
[0015] In a particularly preferred embodiment, the light-emitting
device according to the invention also has a CsF interlayer between
the cathode and the emitter layer or an electron-conductor layer.
This layer has, in particular, a thickness of 0.5 nm to 2 nm,
preferably about 1 nm. This interlayer predominantly causes a
reduction in the electron work function.
[0016] The light-emitting device is furthermore preferably applied
to a substrate, for example to a glass substrate.
[0017] In a particularly preferred embodiment, an OLED structure
for a sublimable emitter according to the invention comprises,
besides an anode, emitter layer and cathode, also at least one, in
particular a plurality of and particularly preferably all the
layers mentioned below and shown in FIG. 1B.
[0018] The entire structure is preferably located on a support
material, where, in particular, glass or any other solid or
flexible transparent material can be employed for this purpose. The
anode, for example an indium tin oxide anode (ITO), is arranged on
the support material. A hole-transport layer (HTL), for example
.alpha.-NPD, is arranged on the anode and between the emitter layer
and the anode. The thickness of the hole-transport layer is
preferably 10 to 100 nm, in particular 30 to 50 nm. Further layers
which improve hole-injection, for example a copper phthalocyanine
(CuPc) layer, may be arranged between the anode and the
hole-transport layer. This additional layer preferably has a
thickness of 5 to 50 nm, in particular 8 to 15 nm. An
electron-blocking layer, which ensures that electron transport to
the anode is suppressed since a current of this type would only
cause ohmic losses, is preferably applied to the hole-transport
layer and between the hole-transport layer and the emitter layer.
The thickness of this electron-blocking layer is preferably 10 to
100 nm, in particular 20 to 40 nm. This additional layer can be
omitted, in particular, if the HTL layer is already intrinsically a
poor electron conductor.
[0019] The next layer is the emitter layer, which comprises or
consists of the emitter material according to the invention. In the
embodiment using sublimable emitters, the emitter materials are
preferably applied by sublimation. The layer thickness is
preferably between 10 nm and 200 nm, in particular between 50 nm
and 150 nm. The emitter material according to the invention may
also be co-evaporated together with other materials, in particular
with matrix materials. For emitter materials according to the
invention which emit in the green or red, common matrix materials
such as PVK or CBP are suitable. However, it is also possible to
construct a 100% emitter material layer. For emitter materials
according to the invention which emit in the blue, UHG matrix
materials are preferably employed (cf. M. E. Thompson et al., Chem.
Mater. 2004, 16, 4743). In order to produce light of mixed colour
on use of compounds according to the invention with different metal
central ions, coevaporation can likewise be used.
[0020] In principle, it is possible to employ in accordance with
the invention common matrix materials for OLEDs, but also
substantially inert polymers or small matrix molecules without
particularly pronounced hole or electron mobilities as matrix
materials.
[0021] A hole-blocking layer, which reduces ohmic losses which
could arise due to hole currents to the cathode, is preferably
applied to the emitter layer. This hole-blocking layer preferably
has a thickness of 10 to 50 nm, in particular 15 to 25 nm. A
suitable material for this purpose is, for example, BCP
(4,7-diphenyl-2,9-dimethylphenanthroline, also known as
bathocuproin). An ETL layer comprising electron-transport material
(ETL=electron-transport layer) is preferably applied to the
hole-blocking layer and between this layer and the cathode. This
layer preferably consists of vapour-depositable Alq.sub.3 having a
thickness of 10 to 100 nm, in particular 30 to 50 nm. An
interlayer, for example of CsF or LiF, is preferably applied
between the ETL layer and the cathode. This interlayer reduces the
electron-injection barrier and protects the ETL layer. This layer
is generally applied by vapour deposition. The interlayer is
preferably very thin, in particular having a thickness of 0.2 to 5
nm, more preferably 0.5 to 2 nm. Finally, a conductive cathode
layer is also applied by vapour deposition, in particular having a
thickness of 50 to 500 nm, more preferably 100 to 250 nm. The
cathode layer preferably consists of Al, Mg/Ag (in particular in
the ratio 10:1) or other metals. Voltages of between 3 and 15 V are
preferably applied to the OLED structure described for a sublimable
emitter according to the invention.
[0022] The OLED device can also be manufactured partially by
wet-chemical methods, for example with the following structure:
glass substrate, transparent ITO layer (of indium tin oxide), for
example PEDOT/PSS (polyethylenedioxythiophene/polystyrenesulfonic
acid, for example 40 nm) or other layers which improve hole
injection, 100% complex according to the invention (for example 10
to 80 nm) or doped (for example 1%, in particular 4% to 10%) into a
suitable matrix (for example 40 nm), vapour-deposited Alq.sub.3
(for example 40 nm), vapour-deposited LiF or CsF as protective
layer (for example 0.8 nm), vapour-deposited metal cathode Al or Ag
or Mg/Ag (for example 200 nm).
[0023] An OLED structure for a soluble emitter according to the
invention particularly preferably has the structure described below
and shown in FIG. 1C, but comprises at least one, more preferably
at least two and most preferably all the layers mentioned
below.
[0024] The device is preferably applied to a support material, in
particular to glass or another solid or flexible transparent
material. An anode, for example an indium tin oxide anode, is
applied to the support material. The layer thickness of the anode
is preferably 10 nm to 100 nm, in particular 30 to 50 nm. An HTL
layer of a hole-conductor material, in particular of a
hole-conductor material which is water-soluble, is applied to the
anode and between the anode and the emitter layer. A hole-conductor
material of this type is, for example, PEDOT/PSS
(polyethylenedioxythiophene/poly-styrenesulfonic acid) or novel HTL
materials (DuPont) for extending the device lifetime. The layer
thickness of the HTL layer is preferably 10 to 100 nm, in
particular 40 to 60 nm. The emitter layer (EML) which comprises a
soluble emitter according to the invention is applied next. The
material can be dissolved in a solvent, for example in acetone,
dichloromethane or acetonitrile. This may prevent dissolution of
the underlying PEDOT/PSS layer. The emitter material according to
the invention can be employed in low concentration, for example 2
to 10% by weight, but also in higher concentration or as a 100%
layer. It is also possible to apply the emitter material highly or
moderately doped in a suitable polymer layer (for example PVK). For
low-solubility emitter materials according to the invention,
application by means of a colloidal suspension in a polymer can be
carried out. Oligomer strands can be comminuted with ultrasound
treatment before introduction into the polymer and introduced into
the polymer after filtering through nanofilters. The emitter layer
preferably has a layer thickness of 10 to 80 nm, in particular 20
to 60 nm. A layer of electron-transport material is preferably
applied to the emitter layer, in particular with a layer thickness
of 10 to 80 nm, more preferably 30 to 50 nm. A suitable material
for the electron-transport material layer is, for example,
Alq.sub.3, which can be applied by vapour deposition. A thin
interlayer which reduces the electron-injection barrier and
protects the ETL layer is preferably applied next. This layer
preferably has a thickness of between 0.1 and 2 nm, in particular
between 0.5 and 1.5 nm, and preferably consists of CsF or LiF. This
layer is generally applied by vapour deposition. For a further
simplified OLED structure, the ETL layer and/or the interlayer may
optionally be omitted.
[0025] Finally, a conductive cathode layer is applied, in
particular by vapour deposition. The cathode layer preferably
consists of a metal, in particular of Al or Mg/Ag (in particular in
the ratio 10:1).
[0026] Voltages of 3 to 15 V are preferably applied to the
device.
[0027] It is essential to the invention that the light-emitting
device comprises at least one complex of the formula (I) as
emitter.
[0028] Free biphenyl exhibits fluorescence between 300 and 350 nm
on excitation in the UV (cf. I. B. Berlman, Handbook of
Fluorescence Spectra of Aromatic Molecules, Academic Press, 1971)
and phosphorescence at 433 nm (in butyronitrile, 77 K, but not at
room temperature), (cf. M. Maestri et al., Helv. Chim. Acta 1988,
71, 1053). Owing to the steric interaction of the ortho-hydrogen
atoms, the two phenyl groups are twisted relative to one another,
reducing the conjugation length. In the case of coordination in the
2,2'-position at a single centre, the rings are planarised, and the
1-system becomes larger. For this reason, emissions in the visible
region are to be expected. As ligand in complexes of heavy
transition metals, the strong spin-track coupling enables effective
phosphorescence to be obtained, which facilitates use as triplet
emitter in OLED devices. 2,2'-Biphenyl complexes of platinum are a
class of compounds which has been well investigated. The first
(bph)Pt compound was (bph)Pt(NBD), which was synthesised by Gardner
et al. and which they were able to obtain in very low yield from
(NBD)PtCl.sub.2 and 2,2'-dilithiobiphenyl
(bph=.eta..sup.2-biphenyl-2,2'-diyl NBD=norbornadiene), (cf. S. A.
Gardner, H. B. Gordon, M. D. Rausch, J. Organomet. Chem. 1973, 60,
179). A method which can be used preparatively was presented by
Uson et al. with the synthesis of (bph)Pt(COD) from
(bph)Sn(.sup.nPr).sub.2 and [PtCl.sub.2(COD)], where
COD=cyclooctadiene and .sup.nPr=n-propyl (cf. R. Uson et al., J.
Organomet. Chem. 1980, 198, 105). Further derivatives were
subsequently prepared by this method and by the reaction of
2,2'-dilithiobiphenyl with trans-[PtCl.sub.2(Et.sub.2S).sub.2] (cf.
C. Cornioley-Deuschel, A. von Zelewsky, Inorg. Chem., 1987, 26,
3354 and H.-A. Brune et al., J. Organomet Chem. 1991, 402, 179). A
multiplicity of studies is subsequently concerned with syntheses
(cf. H.-A. Brune et al., J. Organomet. Chem. 1991, 412, 237; B. L.
Edelbach et al., Organometallics 1998, 17, 4784, R. E. Marsh, Acta
Crsystallogr., Sect B: Struct. Sci. 1997, 53, 317; A. C. Stuck et
al., Z. Kristallogr 1993, 208, 294; A. C. Stuckl et al.,
Kristallogr 1993, 208, 302; X Zhang et al., Organometallics 1999,
18, 4887; J. DePriest et al., Inorg. Chem. 2000, 39, 1955; B. L.
Edelbach et al., J. Am. Chem. Soc. 1998, 120 2843; Y.-H. Chen et
al., Inorg. Chim. Acta 1995, 240, 41; Y. Chen et al., J. Chem.
Cryst. 1996, 26, 527; H.-A. Brune et al., J. Organomet. Chem. 1991,
402, 435; G. Y. Zheng et al., Inorg. Chem. 1999, 38, 794; N. Simhai
et al., Organometallics 2001, 20, 2759; C. B. Blanton et al.,
Inorg. Chem. 1992, 31, 3230; C. B. Blanton et al., Inorg. Chim.
Acta 1990, 168, 145; C. N. Iverson et al., Organometallics 2002,
21, 5320), solid-state structures (cf. B. L. Edelbach et al.,
Organometallics 1998, 17, 4784; X Zhang et al., Organometallics,
1999, 18, 4887; J. DePriest et al., Inorg. Chem. 2000, 39, 1955; B.
L. Edelbach et al., J. Am. Chem. Soc. 1998, 120, 2843; Y.-H. Chen
et al., Inorg. Chim. Acta 1995, 240, 41; Y. Chen et al., J. Chem.
Cryst. 1996, 26, 527; H.-A. Brune et al., J. Organomet. Chem. 1991,
402, 435; G. Y. Zheng et al., Inorg. Chem. 1999, 38, 794; N. Simhai
et al., Organometallics 2001, 20, 2759; M. A. Bennett et al., J.
Chem. Soc., Dalton Trans. 1998, 217; T. Debaerdemaeker et al., J.
Organomet. Chem. 1991, 412, 243; T. Debaerdemaeker et al., J.
Organomet. Chem. 1991, 410, 265; K. Yu et al., Organometallics
2001, 20, 3550; T. Debaerdemaeker et al., J. Organomet. Chem. 1988,
350, 109), reactivities (cf. C. Cornioley-Deuschel, A. von
Zelewsky, Inorg. Chem. 1987, 26, 3354; X Zhang et al.
Organometallics 7999, 18, 4887; B. L. Edelbach et al., J. Am. Chem.
Soc. 1998, 120, 2843; Y.-H. Chen et al., Inorg. Chim. Acta 1995,
240, 41; N. Simhai et al., Organometallics 2001, 20, 2759; K. Yu et
al., Organometallics 2001, 20, 3550; M. R. Plutino et al., Inorg.
Chem. 2000, 39, 2712; M. R. Plutino et al., J. Am. Chem. Soc. 2004,
126, 6470), and spectroscopic properties (cf. M. Maestri et al.,
Helv. Chim. Acta 1988, 71, 1053; C. Cornioley-Deuschel, A. von
Zelewsky, Inorg. Chem. 1987, 26, 3354; H.-A. Brune et al., J.
Organomet. Chem. 1991, 402, 179; J. DePriest et al., Inorg. Chem.
2000, 39, 1955; Y.-H. Chen et al., Inorg. Chim. Acta 1995, 240, 41;
Y. Chen et al., J. Chem. Cryst. 1996, 26, 527; G. Y. Zheng et al.,
Inorg. Chem. 1999, 38, 794; C. B. Blanton et al., Inorg. Chem.
1992, 31, 3230; C. B. Blanton et al., Inorg. Chim. Acta 1990, 168,
145; G. Y. Zheng et al., Inorg. Chem. 1998, 37, 1392; S. R.
Stoyanov et al., Inorg. Chem. 2003, 42, 7852) of complexes in which
both the biphenyl group has been modified by substitution and also
the COD has been replaced by other ligands.
[0029] Surprisingly, it has now been found in accordance with the
invention that compounds of the formula (I) are eminently suitable
as emitter molecules for light-emitting devices and in particular
for organic light-emitting devices (OLEDs).
[0030] In accordance with the invention, the emitter molecules
employed are complexes of the formula (I) (s-bph)ML. These
complexes are, in particular, luminescent compounds. The complexes
have a central atom selected from Pt, Rh, Ir, Pd and Au. The
central atom is preferably in the form of Pt(II), Rh(I), Ir(I),
Pd(II) or Au(III), i.e. in the form of a singly or doubly or triply
positively charged ion. The central atom is particularly preferably
Pt(II). In accordance with the invention, the central atom is
tetracoordinated, with, in particular, square-planar complexes
being involved. Tetracoordinated complexes with 16 valence
electrons, in particular with Pt(II), are particularly
favourable.
[0031] Furthermore, the complex employed in accordance with the
invention includes a group L, which is a bidentate ligand, or the
group X.sub.2, where each X, independently, represents a
monodentate ligand. In a first preferred embodiment, L is a bulky
ligand. If the complex centre M is sufficiently screened by bulky
ligands or a complex arrangement with short M-M separations is
prevented, M-M interactions cannot form in the solid or in
concentrated solutions. Steric screening by the ligand L may in
addition cause a reduction in quench processes and consequently an
increase in the photoluminescence quantum yield. Suitable bulky
ligands L are, for example, bidentate phosphines, amines, arsines
or dienes. When selecting preferred ligands L, the criteria of
bulk, high ligand field strength and stability of the resultant
complexes as well as high-energy triplet level, in particular, are
taken into account.
[0032] Examples of preferred ligands L, which are each neutral and
bond in a bidentate manner (chelates), are:
##STR00001## ##STR00002##
where the phosphorus atoms may each be replaced, independently, by
nitrogen atoms or arsenic atoms and where R in each case represents
hydrogen, an alkyl, aryl, alkoxy, aryloxy, alkylamine or arylamine
group, which may optionally be substituted or/and may have one or
more heteroatoms. The heteroatoms are, in particular, selected from
O, S, N, P, Si and/or Se. Suitable substituents are, for example,
halogen, in particular F, Cl, Br or I, alkyl, in particular C.sub.1
to C.sub.20, more preferably C.sub.1 to C.sub.6-alkyl, aryl, OR, SR
or PR.sub.2. In many cases, it is preferred for L to contain at
least one fluorine atom as substituent in order to increase the
volatility of the complex.
[0033] Unless indicated otherwise, the term alkyl or Alk, as used
herein, in each case, independently, denotes a C.sub.1-C.sub.20, in
particular a C.sub.1-C.sub.6 hydrocarbon group. The hydrocarbon
groups may be linear or branched and may be saturated or have one
or more C.dbd.C double bonds.
[0034] The term aryl denotes an aromatic system having 5 to, for
example, 20 C atoms, in particular having 6 to 10 C atoms, in which
one or more C atoms may optionally be replaced by heteroatoms (for
example N, S, O).
Polymer-Bound Emitters/Monomer or Oligomer Emitters
[0035] In a further preferred embodiment, the complex of the
formula (I) (s-bph)ML present in accordance with the invention in
the emitter layer originates from a complex of the formula
(III)
(s-bph)ML',
where L' represents a ligand which has a polymerisable group. The
(s-bph)ML complex here may be immobilised on a polymer by
functionalisation of the ligand L by means of a polymerisable
group. This demobilises the complex, preventing undesired
crystallisation of the emitter in the emitter layer, which is
frequently a reason for a limited device lifetime of OLEDs. In this
embodiment, the complex of the formula (I) is bonded to a polymer
in the emitter layer via the polymerisable ligand. The bonding to a
polymer enables a homogeneous distribution of the emitter in the
emitter layer and in addition reliable control of the complex
content to be achieved. In order to provide the light-emitting
devices according to the invention, a polymer which contains
(s-bph)ML' groups bonded as units can firstly be prepared and then
applied, for example as a solution by means of spin coating or
ink-jet printing. However, it is also possible for a monomer to be
applied and polymerised on site. Suitable ligands L' include, for
example, the ligands L indicated above, which additionally contain
a radical which is polymerisable, for example a C.dbd.C radical.
The following ligands L' are particularly preferred.
##STR00003##
in which R is as defined above.
[0036] The phosphine CH.sub.2.dbd.C(PR.sub.2).sub.2 is commercially
available. Through complexing to a metal, the .beta.-function
attains a positive partial charge and is therefore activated for
nucleophilic attack. This group can therefore be attached to a
polymer or can serve as monomer unit for the construction of a
polymer, where the monomers to be reacted with the phosphine are,
in particular, nucleophiles, such as, for example, alcohols,
thiols, primary amines or phosphines, silanes or boranes which have
been functionalised by means of a vinyl group. Also possible is
attachment to a polymer which has been functionalised by means of a
nucleophilic group, for example to polyvinyl alcohol. The other
phosphine indicated can be prepared from
bis(diphenylphosphino)methane by reaction with n-butyllithium and
p-vinylbenzyl chloride and can be polymerised by means of free
radicals, anionically, canonically or catalytically.
[0037] The invention furthermore relates to a complex of the
formula (III)
(s-bph)ML'
in which M represents Pt(II), Rh(I), Ir(I), Pd(II) or Au(III), and
L' represents a bidentate ligand or L'=X'.sub.2, where each X',
independently, represents a monodentate ligand, where L' or at
least one X' contains a polymerisable group, and sbph represents a
ligand which has an Ar--Ar group, where Ar represents an aromatic
ring system.
Emitters Containing Small Ligands/Oligomer Emitters
[0038] In a further embodiment, the emitter layer comprises a
complex of the formula (I) in which L=L* as a complex of the
formula (s-bph)ML*. The ligand L* is a non-bulky ligand. On use of
complexes containing a non-bulky ligand L*, M-M interactions can
form in the solid and in the emitter layers with doping of
relatively high concentration, resulting in intense photo- or
electroluminescence. In this embodiment, the emitter layer
comprises complexes of the formula (I) in a concentration of, for
example, >10% by weight, based on the total weight of the
emitter layer, in particular >20% by weight, more preferably
>50% by weight, in particular >80% by weight and most
preferably >90% by weight. However, it is also possible to
produce emitter layers which consist virtually completely of
complexes of the formula (I) and in particular comprise >95% by
weight, more preferably >99% by weight. In a further embodiment,
the emitter layer consists completely, i.e. 100%, of complexes of
the formula (I).
[0039] On use of the complexes according to the invention in high
concentration in the emitter layer, stacks of the complexes with
relatively short metal-metal separations form. Such stacks are
formed, in particular, in the case of planar complexes and
particularly favourably in the case of planar platinum complexes.
In these stacks, strong electronic interactions occur, resulting in
completely different emission behaviour than in the case of the
monomers. The emission wavelength here is determined by the M-M
separation and can be determined in a simple manner by substitution
on the (s-bph) group or through the type of ligand L*. The use of
highly concentrated emitter layers and in particular crystalline or
quasi-crystalline layers offers considerable advantages. In
particular, no concentration variations occur during manufacture or
they have only small effects in highly concentrated systems.
Furthermore, the charge-carrier mobilities, i.e. the electron or
hole mobilities, are significantly greater in the case of the
formation of crystalline layers than in amorphous layers. In
addition, the electronic interaction between the molecules in the
oligomers results in a raising of the HOMO and thus improved hole
conductivity and a lowering of the LUMO and thus improved electron
conductivity.
[0040] Furthermore, a high luminous density and high efficiency,
i.e. a high quantum efficiency, can be achieved with concentrated
emitter layers of this type at high current densities. The emitter
complexes employed in accordance with the invention have extremely
intense emission with high emission quantum yield due to
metal-metal interactions between the central atoms of the
individual complexes, in particular owing to metal-metal
interactions between planar metal complexes. The emission is thus
effected by the interaction of the complexes present in high
concentration. In contrast to materials of the prior art, emitter
layers having a high proportion of emitter molecules and
crystalline emitter layers or emitter layers with quasi-crystalline
ordering can thus be produced from uniform units. The use of
emitter molecules from the prior art in high concentrations has
hitherto not resulted in high-efficiency emitter materials since,
in particular, an electronic interaction of adjacent emitter
molecules has resulted in self-extinguishing effects. This has the
consequence that the emission quantum yield decreases significantly
with increasing concentration of the emitter molecules, in
particular from a concentration of >10% by weight.
Correspondingly, OLEDs are currently only produced in the prior art
with emitter molecule concentrations of about 2 to 8% by weight.
Due to the stack formation observed in the case of the compounds
employed in accordance with the invention, however, the problems
occurring in the prior art are at least partially overcome.
[0041] However, the use of high concentrations of emitter molecules
in the emitter layer and in particular the provision of crystalline
emitter layers or emitter layers with quasi-crystalline ordering
provides a number of significant advantages: [0042] An emitter
layer structure comprising uniform material results in a clearly
defined and easily reproducible manufacturing situation. [0043]
Slight changes in the molecules employed allow the setting of
different metal-metal separations and thus interactions of
different strength between the complexes. This results in the
possibility of tuning the emission colour from green to red and to
the near IR. It is of particular importance that virtually any
desired colour can be set by slight chemical variation of the
emitter molecules. [0044] The emitter layers can be produced simply
by vacuum sublimation methods (and if necessary subsequently gentle
conditioning). [0045] The emitter monomer materials have good
solubility in many solvents. These crystalline or quasi-crystalline
emitter layers can thus also be produced by spin coating or ink-jet
printing methods. [0046] The emission quantum yields are very high.
[0047] The monomers also have good suitability for chemical linking
to polymers. In adjacent monomers, metal-metal interactions can
again result in the desired excellent emission properties. [0048]
The substances have extremely high chemical stability, which
results in high OLED long-term stability. [0049] Due to the
metal-metal interactions, the HOMO and the LUMO are electronically
delocalised over a large number of molecules (units of the
oligomer). This results in a significant improvement in the hole
and electron mobility. As a consequence, the emission layer (EML)
does not require any additional components for improving the
charge-carrier mobility, i.e. the in some cases restrictive
requirements of the matrix regarding good charge-carrier mobility
are superfluous on use of oligomer emitters. [0050] Specific mixing
of different materials (for example (s-bph)Pt(CO).sub.2 with
(s-bph)Pd(CO).sub.2), at least one substance of which is described
by the formula (I), allows further, independent variation of the
properties.
[0051] L* can be a flat, neutral or singly or doubly charged
bidentate ligand or two monodentate ligands. L* is preferably
CN--B--NC, NC--B--CN, diimines, acetylacetonate,
[RN--CR'.dbd.CH--CR'.dbd.NR].sup.-, 2,2'-biphenylylene,
[CH.dbd.CR--B--CR.dbd.CH].sup.2- or
[C.ident.C--B--C.ident.C].sup.2-, where B is a bridging group,
which is an alkylene or arylene group, which may be substituted
or/and may contain heteroatoms (for example N, O, P or/and S). In
the case where L*=X*.sub.2, X* preferably represents CO, CNR, NCR,
RN--CR', SCNR, NCSR, NCOR, CN.sup.-, SCN.sup.-, OCN.sup.-, F.sup.-,
Cl.sup.-, Br.sup.-, I.sup.-, .sup.-CH.dbd.CRR.sup.1,
.sup.-C.ident.CR, alkyl, aryl, heteroaryl groups, --OR, --SR,
--SeR, --NR.sub.2, --PR.sub.2, --SiR.sub.3, where R and R' each,
independently, preferably represent an alkyl or aryl radical, in
particular having 1 to 10, more preferably having 1 to 6 C
atoms.
[0052] The emitter complexes according to the invention having a
columnar structure are particularly preferably employed. This
structure forms, in particular, at high concentrations of the
emitter complexes in the emitter layer since, as stated above, the
complexes according to the invention themselves have a planar
structure. This enables stacking and the formation of columnar
structures. The individual complexes themselves can be neutral,
positively or negatively charged and thus preferably have the
formula [(s-bph)ML].sup.n+/m-, in which n and m each represent an
integer from 0 to 5, more preferably from 0 to 3, and in particular
from 1 to 2. The central atom M here is preferably selected from
the group Rh(I), Ir(I), Pd(II), Pt(II) and Au(III) and is, in
particular, Pt(II). A further variation can be achieved through the
formation of columnar structures from different complexes of the
formula (I). All ligands and the central atom here can be varied
independently of one another, where the complexes can also have, in
particular, different charges. In a particular embodiment, columnar
salts are prepared, for example of the type
[(sbph)ML*].sup.m+[(s'-bph)M'L*'].sup.m-, where s'-bph, M' and L*'
can each have the meanings indicated under s-bph, M and L*, but
where at least one of these groups has been varied compared with
the positively charged complex.
[0053] In the case where L=X.sub.2, each X, independently,
preferably represents a ligand selected from the group consisting
of F.sup.-, Cl.sup.-, Br.sup.-, I.sup.-, CN.sup.-, R'', OR'', SR''
and PR''.sub.2, where each R'', independently, represents an alkyl
or aryl group, which may be substituted or/and may have heteroatoms
(for example O, N, S, P), where R'' represents, in particular, Me,
Et, n-Pr, i-Pr, n-Bu, t-Bu, i-Bu, Bz, Ph, m-Tol, p-Tol, o-Tol,
m-PhCl, p-PhCl, o-PhCl, m-PhF, p-PhF, o-PhF or C.sub.6H.sub.5.
[0054] The complexes according to the invention furthermore contain
a ligand s-bph which has an Ar--Ar group, where Ar represents an
aromatic ring system, which is independent in each case. Ar can be
fused to further aromatic rings or contain one or more heteroatoms
and optionally be substituted. Suitable heteroatoms are, for
example, O, N and S. Suitable substituents are, for example,
halogen, in particular F, Cl, Br or C.sub.1-C.sub.6-alkyl radicals,
in particular methyl or t-butyl. Ar is preferably phenyl, thienyl,
furyl or pyrrole systems. The Ar--Ar group particularly preferably
has one of the following formulae:
##STR00004##
in which R can represent H, alkyl, aryl, heteroaryl, alkenyl or
alkynyl.
[0055] The ligand s-bph preferably has the formula (II)
##STR00005##
where * represent the metal coordination sites to M, and R.sup.1 to
R.sup.8 each, independently of one another, represent H, alkyl,
aryl, heteroaryl, alkenyl, alkynyl, halogen, --NR.sub.2,
--PR.sub.2, --OR or --SR, where R represents H, alkyl, aryl,
heteroaryl, alkenyl or alkynyl. The substituents R.sup.1 to R.sup.8
may be linked to one another and thus form additional aliphatic,
aromatic or heteroaromatic rings.
[0056] Particularly preferred examples of the ligand s-bph are
unsubstituted biphenyl and
##STR00006## ##STR00007##
[0057] Asymmetrical ligands (not shown) are also advantageous.
[0058] The complexes employed in accordance with the invention as
emitters can be tuned in the wavelength range in a simple manner
(through choice of suitable matrix materials) and particularly
through the choice of electron-withdrawing or -donating
substituents.
[0059] Preference is given to the use of compounds which exhibit
emission at a temperature of >-50.degree. C., preferably
>0.degree. C., in particular at >10.degree. C. and still more
preferably at >20.degree. C. and at temperatures of preferably
<100.degree. C., in particular <70.degree. C., more
preferably <50.degree. C., still more preferably <40.degree.
C.,
[0060] Particularly advantageous and preferred oligomer-forming
complexes are
##STR00008##
where the atoms A.sup.1-A.sup.8 are each selected, independently,
from C, N, O and S, and in particular the ligands R.sup.1-R.sup.3
each, independently, represent H, CH.sub.3, C.sub.2H.sub.5,
CH(CH.sub.3).sub.2, C(CH.sub.3).sub.3, CF.sub.3, C.sub.nH.sub.2n+1,
F, CN, OCH.sub.3, OC.sub.nH.sub.2n+1, SCH.sub.3,
SC.sub.nH.sub.2n+1, N(CH.sub.3).sub.2,
N(C.sub.nH.sub.2n+1)(C.sub.nH.sub.2n+1), where n=1 to 20, where two
or more of the radicals R.sup.1 to R.sup.8 may also be linked to
one another and thus form additional aliphatic, aromatic or
heteroaromatic rings, and the ligands L.sup.1 and L.sup.2 each,
independently, represent CO, NC--CH.sub.3, NC--CH(CH.sub.3).sub.2,
NC--C.sub.nH.sub.2n+1, CN--CH.sub.3, CN--CH(CH.sub.3).sub.2,
CN--C(CH.sub.3).sub.3, NC--C.sub.nH.sub.2n+1, P(CH.sub.3).sub.3,
As(CH.sub.3).sub.3, N(CH.sub.3).sub.2, where the ligands L.sup.1
and L.sup.2 may also be parts of a chelate ligand, for example
(NC).sub.2C.sub.3H.sub.7.
[0061] Particular preference is given to the complexes:
##STR00009##
[0062] The emission spectra of these complexes are shown in FIGS.
5-7.
[0063] Further preferred examples are:
##STR00010##
[0064] The ring systems of the biphenyl ligand and of the
heteroaromatic analogues may also be asymmetrically substituted,
which is illustrated by the following examples.
##STR00011##
Emitters Containing Bulky Ligands (Monomer Emitters)
[0065] Advantageous and preferred monomer complexes containing
bulky ligands are
##STR00012##
where the atoms A.sup.1-A.sup.8 are each selected, independently,
from C, N, O, S, the ligands R.sup.1-R.sup.8 each, independently,
represent H, CH.sub.3, C.sub.2H.sub.5, CH(CH.sub.3).sub.2,
C(CH.sub.3).sub.3, CF.sub.3, C.sub.nH.sub.2n+1, F, CN, OCH.sub.3,
OC.sub.nH.sub.2n+1, SCH.sub.3, SC.sub.nH.sub.2n+1,
N(CH.sub.3).sub.2, N(C.sub.nH.sub.2n+1)(C.sub.nH.sub.2n+1), where
n=1 to 20, where two or more of the radicals R.sup.1 to R.sup.8 may
be linked to one another and thus form additional aliphatic,
aromatic or heteroaromatic rings, and L.sup.1.andgate.L.sup.2
represents diphosphine, diamine, diarsine or diene, in particular a
linear or cyclic diene having 6 to 10 C atoms or a diphosphine
selected from
##STR00013## ##STR00014##
where R represents alkyl, aryl, alkoxy, phenoxy, alkylamine or
arylamine. L.sup.1.andgate.L.sup.2 preferably represents
Ph.sub.2P--CH.sub.2--CH.sub.2--PPh.sub.2 or cyclooctadiene.
[0066] Particular preference is given in accordance with the
invention to the compounds (biphenyl)(cyclooctadiene)platinum,
(bph)Pt(COD), or (biphenyl)(bis(diphenylphosphino)ethane)platinum,
(bph)Pt(dppe)
##STR00015##
[0067] The emission spectra of these compounds are shown in FIGS. 3
and 4.
[0068] Further particularly preferred compounds are
##STR00016## ##STR00017##
[0069] The invention furthermore relates to the use of a compound
of the formula (I) as defined herein as emitter of a light-emitting
device, in particular in an organic light-emitting device.
[0070] The invention is explained in greater detail by the attached
figures and the examples below.
[0071] FIG. 1A shows an example of an OLED device manufactured by
means of vacuum sublimation
[0072] FIG. 1C shows an example of an OLED device with emitters
according to the invention which are applied by wet-chemical
methods.
[0073] FIG. 2 shows the emission properties and electrochemical
data of biphenyl-Pt(II) complexes.
[0074] FIGS. 3 and 4 show the emission spectra of two examples
[(bph)Pt(COD) and (bph)Pt(dppe)]. Monomer emission occurs here
owing to the bulky is ligands. Both compounds exhibit yellow or
yellow-green emission, which is strongly red-shifted compared with
the fluorescence of biphenyl. Owing to the structuring of the
emission bands and the lifetimes in the .mu.s region,
phosphorescence can be assumed, resulting to an approximation from
an intraligand transition.
[0075] FIG. 5 shows the emission of a vacuum-sublimed layer of
(bph)Pt(CO).sub.2 at 300 K. Oligomer emission (stack emission)
occurs here owing to the small ligands.
[0076] FIGS. 6 and 7 show the emission spectra of
(d.sup.tBubph)Pt(CO).sub.2 and of (tmbph)Pt(CO).sub.2.
Preparation of Selected Biphenyl-Pt(II) Complexes
##STR00018##
[0077] [nBuLi Stands for .sup.nbutyllithium]
[0078] Biphenyl-Pt(II) complexes are prepared from
2,2'-dilithiobiphenyl (from 2,2'-dibromobiphenyl and nBuLi) and
cis-[(Et.sub.2S).sub.2PtCl.sub.2]. The diethyl sulfide complex 1
present in situ is not isolated since experience suggests that the
purification would result in large losses, but instead is
converted, by passing in carbon monoxide, directly into the
dicarbonyl compound 2, which precipitates out of the reaction
solution as a green precipitate. The complex 2 is a highly suitable
starting compound for the synthesis of further derivatives since
the carbon monoxide can be replaced very simply by other ligands.
For example, vigorous evolution of gas is observed on addition of
diphosphines or COD to a suspension of 2, and the complexes 3 and 4
can be isolated in high yields and high purity.
* * * * *