U.S. patent application number 13/389783 was filed with the patent office on 2012-10-18 for organic electroluminescent device.
This patent application is currently assigned to Commonwealth Scientific and Industrial Research Organisation. Invention is credited to Mark Bown, Tadahiko Hirai, James Matthew MacDonald, Jenny Lee O'Connell, Kazunori Ueno, Karl Peter Weber.
Application Number | 20120261650 13/389783 |
Document ID | / |
Family ID | 45974563 |
Filed Date | 2012-10-18 |
United States Patent
Application |
20120261650 |
Kind Code |
A1 |
MacDonald; James Matthew ;
et al. |
October 18, 2012 |
ORGANIC ELECTROLUMINESCENT DEVICE
Abstract
An organic electroluminescent device comprising: a pair of
electrodes comprising an anode and a cathode, and one or more
layers arranged between the anode and the cathode; wherein at least
one of the one or more layers is a light emitting layer and wherein
the one or more layers, comprises an organic compound represented
by a substituted 2,2'-biimidazole. The substitutents on the
biimidazole may be selected form a range of suitable substituents,
including: hydrogen, a substituted or unsubstituted heterocyclic
group, a substituted or unsubstituted alkyl group, a substituted or
unsubstituted aralkyl group, a substituted aryl group containing at
least one atom selected from the group consisting of N, O, S, Si,
P, F, Cl, Br; and/or comprising at least three organic rings, the
organic rings being fused or non-fused, or a number of the adjacent
substituent sites may together form a substituted or unsubstituted
cyclic group; furthermore some substituents may be the same or
different and may be selected from the group consisting of:
hydrogen, deuterium, a substituted or unsubstituted alkyl group, a
halogen atom or a cyano group.
Inventors: |
MacDonald; James Matthew;
(Oakleigh South, AU) ; Bown; Mark; (Notting Hill,
AU) ; Ueno; Kazunori; (Burwood, AU) ; Weber;
Karl Peter; (Surrey Hills, AU) ; O'Connell; Jenny
Lee; (Oakleigh East,, AU) ; Hirai; Tadahiko;
(Mount Waverley, AU) |
Assignee: |
Commonwealth Scientific and
Industrial Research Organisation
Campbell, Australian Capital Territory
AU
|
Family ID: |
45974563 |
Appl. No.: |
13/389783 |
Filed: |
October 21, 2011 |
PCT Filed: |
October 21, 2011 |
PCT NO: |
PCT/AU2011/001343 |
371 Date: |
February 9, 2012 |
Current U.S.
Class: |
257/40 ;
257/E51.026; 540/471; 544/42; 546/256; 548/110; 548/112; 548/313.1;
548/313.4 |
Current CPC
Class: |
C07D 405/14 20130101;
C09K 11/06 20130101; H01L 51/0059 20130101; H05B 33/10 20130101;
C07D 401/14 20130101; C07D 403/14 20130101; H01L 51/0067 20130101;
H01L 51/5016 20130101; C09K 2211/1011 20130101; C09K 2211/1029
20130101; C09K 2211/1037 20130101; C07D 417/14 20130101; C07D
409/14 20130101; C09K 2211/1044 20130101; C07F 9/6506 20130101;
Y10S 428/917 20130101; H01L 51/0085 20130101; C07D 233/61 20130101;
C09K 2211/1014 20130101; C09K 2211/1007 20130101; C07D 487/16
20130101; C07F 7/081 20130101; C09K 2211/1088 20130101; H01L
51/0072 20130101; C09K 2211/1092 20130101 |
Class at
Publication: |
257/40 ;
548/313.1; 548/313.4; 546/256; 544/42; 548/110; 548/112; 540/471;
257/E51.026 |
International
Class: |
H01L 51/54 20060101
H01L051/54; C07D 233/90 20060101 C07D233/90; C07D 401/14 20060101
C07D401/14; C07D 417/14 20060101 C07D417/14; C07D 471/22 20060101
C07D471/22; C07D 409/14 20060101 C07D409/14; C07F 7/10 20060101
C07F007/10; C07F 9/6506 20060101 C07F009/6506; C07D 487/14 20060101
C07D487/14; C07D 403/14 20060101 C07D403/14; C07D 405/14 20060101
C07D405/14 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 22, 2010 |
AU |
2010904715 |
Sep 13, 2011 |
AU |
2011903758 |
Claims
1. An organic electroluminescent device comprising: (i) an anode;
(ii) a cathode; and (ii) one or more layers arranged between the
anode and the cathode; wherein at least one of the one or more
layers is a light emitting layer and wherein the one or more
layers, comprises an organic compound represented by the formula:
##STR00024## wherein the substituents R.sub.1 and R.sub.2 are the
same or different and are selected from the group consisting of:
(a) hydrogen, (b) a substituted or unsubstituted heterocyclic
group, (c) a substituted or unsubstituted alkyl group, (d) a
substituted or unsubstituted aralkyl group, (e) a substituted aryl
group containing at least one atom selected from the group
consisting of N, O, S, Si, P, F, Cl, Br; and/or comprising at least
three organic rings, the organic rings being fused or non-fused, or
(f) each of R.sub.1 or R.sub.2 may together form a substituted or
unsubstituted cyclic group; and the substituents R.sub.3, R.sub.4,
R.sub.5 and R.sub.6 are the same or different and are each selected
from the group consisting of: hydrogen, deuterium, a substituted or
unsubstituted alkyl group, a halogen atom or a cyano group.
2. The device of claim 1, wherein the substituents R.sub.3,
R.sub.4, R.sub.5 and R.sub.6 are hydrogen atoms.
3. The device of claim 1 or 2 wherein the substituents R.sub.1 and
R.sub.2 are each selected independently from the group consisting
of a substituted aryl group.
4. The device of claim any one of the preceding claims wherein the
substituents R.sub.1 and R.sub.2 are each selected independently
from the group consisting of a substituted aryl group and contain
at least one N, O, S, Si, P, F, Cl, Br atom.
5. The device of any one of the preceding claims wherein the
substituted aryl group contains at least one atom that is N, the
substituents being selected from the group consisting of:
--NH.sub.2, --NHR, --NRR', --N.dbd.R, --ONRR', --C(.dbd.NH)R,
--C(.dbd.NR)R', --C(.dbd.NH)H, --C(.dbd.NR)H, (RCO).sub.2N--,
--N.sub.3, --N.sub.2R, --OCN, --NCO, --ONO.sub.2, --CN, --NC,
--ONO, --NO.sub.2, --NO, --O.sub.5H.sub.4N; wherein R or R' are
further substituents that may be the same or different.
6. The device of claims 1 to 4 wherein the substituted aryl group
contains at least one atom that is O, the substituents being
selected from the group consisting of: --OH, --COR, --CHO, --COX
where X is a halide, --OCOOR, --COOH, --COOR, --OOH, --OOR, --OR,
--CH(OR)(OH), --C(OR')(OH)R, --CH(OR)(OR'), --C(OR')(OR'')R,
--C(OR)(OR')(OR''), --OC(OR)(OR')(OR''); wherein R, R', R'' are
further substituents that may be the same or different.
7. The device of claims 1 to 4 wherein the substituted aryl group
contains at least one atom that is S, the substituents being
selected from the group consisting of: --SH, --SR, --SSR, --SOR,
--SO.sub.2R, --SO.sub.2H, --SO.sub.3H, --SCN, --NCS, --CSR,
--CSH.
8. The device of claims 1 to 4 wherein the substituted aryl group
contains at least one atom that is Si, the substituents being
selected from the group consisting of: SiRR'R''; wherein R, R', R''
are further substituents that may be the same or different.
9. The device of claims 1 to 4 wherein the substituted aryl group
contains at least one atom that is P, the substituents being
selected from the group consisting of: --PRR', --PORR', --PSRR',
--P(.dbd.O)(OH).sub.2, --OP(.dbd.O)(OH).sub.2, --OPO(OR)(OH),
--OPO(OR)(OR'); wherein R or R' are further substituents that may
be the same or different.
10. The device of claim 1 or 2 wherein R.sub.1 and R.sub.2 are each
selected independently from the group consisting of a substituted
or unsubstituted heterocyclic group.
11. The device of claim 1 or 2 wherein R.sub.1 and R.sub.2 are each
selected independently from the group consisting of a substituted
or unsubstituted alkyl group.
12. The device of claim 1 or 2 wherein R.sub.1 and R.sub.2 are
selected independently from a substituted carbazole.
13. The device of any one of claims 1 to 12 wherein the light
emitting layer comprises a phosphorescent material and a host
material.
14. The device of any one of claims 1 to 12 wherein the light
emitting layer comprises a fluorescent material and a host
material.
15. The device of claim 13 or 14, wherein the host material
comprises the organic compound.
16. The device of claim 13 wherein the phosphorescent material
includes an iridium, osmium, platinum, rhodium, ruthenium, or
palladium constituent.
17. The device of any one of the preceding claims wherein the light
emitting layer has a thickness of between 5 nm to 1 .mu.m.
18. The device of any one of the preceding claims wherein the light
emitting layer has a thickness of between 5 to 50 nm.
19. The device of claim 1, 2 or 10 wherein the heterocyclic groups
are polyheterocyclic.
20. The device of any one of the preceding claims wherein the
organic compound includes at least one fused organic ring.
21. The device of any one of the preceding claims, wherein the
device comprises a display.
22. The device of any one of the preceding claims, wherein the
device comprises a light source.
23. The device of any one of the preceding claims, wherein the
device is a stacked organic electroluminescence device for white
emission, the device containing three stacked emission layers each
containing a different single emitter.
24. The device of any one of claims 1 to 22 wherein the device is a
stacked organic electroluminescence device for white emission, the
device containing two stacked emission layers, wherein at least one
of the layers contains at least two emitters.
25. An organic compound represented by the formula: ##STR00025##
wherein the substituents R.sub.1 and R.sub.2 are the same or
different and are selected from the group consisting of: (a)
hydrogen, (b) a substituted or unsubstituted heterocyclic group,
(c) a substituted or unsubstituted alkyl group, (d) a substituted
or unsubstituted aralkyl group, (e) a substituted aryl group
containing at least one atom selected from the group consisting of
N, O, S, Si, P, F, Cl, Br; and/or comprising at least three organic
rings, the organic rings being fused or non-fused, or (f) each of
R.sub.1 or R.sub.2 may together form a substituted or unsubstituted
cyclic group; and the substituents R.sub.3, R.sub.4, R.sub.5 and
R.sub.6 are the same or different and are each selected from the
group consisting of: hydrogen, deuterium, a substituted or
unsubstituted alkyl group, a halogen atom or a cyano group.
26. The compound of claim 25, wherein the substituents R.sub.3,
R.sub.4, R.sub.5 and R.sub.6 are hydrogen atoms.
27. Use of a compound according to claim 25 in an
electroluminescent device.
28. Use of a compound according to claim 25 as a hole transporting
material.
29. Use of a compound according to claim 25 as an electron
transporting material.
30. Use of a compound according to claim 25 as an emission
material.
31. Use of a compound according to claim 25 as a host material.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to organic electroluminescent
devices, which are sometimes otherwise referred to as organic light
emitting diodes (OLED). Organic electroluminescent devices emit
light on the application of an electric field to one layer or
multiple layers of an organic compound (organic material layer).
The present invention also relates to organic compounds suitable
for use in such devices.
BACKGROUND
[0002] An organic electroluminescent device is generally comprised
of a pair of electrodes forming an anode and a cathode, and one
layer or multiple layers comprising a hole injection layer,
emission layer (with either fluorescent or phosphorescent material)
and electron transporting layer. Into the organic layer(s), holes
and electrons are injected from the anode and the cathode,
respectively, thus resulting in excitons within the emission
material. When the excitons transition to ground state, the organic
luminescence device emits light.
[0003] According to the first study by Eastman Kodak Co. ("Appl.
Phys. Lett", vol. 51, pp. 913 (1987), an organic electroluminescent
device which comprised a layer of an aluminium quinolinol complex
(as electron transporting and luminescent material) and a layer of
a triphenylamine derivative (as a hole transporting material)
resulted in luminescence of about 1,000 cd/m.sup.2 under an
application of a voltage of 10 V. Examples of related U.S. patents
include U.S. Pat. Nos. 4,539,507; 4,720,432 and 4,885,211.
[0004] Further studies by Baldo et al. revealed a promising OLED
using phosphorescent material as dopant. The quantum yield of the
phosphorescent OLED was significantly improved (U.S. Pat. No.
6,830,828).
[0005] In addition to the above-mentioned OLED, polymer organic
electroluminescent device (PLED) using a conjugated polymer
material has been reported by a group from Cambridge University
(Nature, vol. 347, pp. 539-(1990), U.S. Pat. Nos. 5,247,190;
5,514,878 and 5,672,678).
[0006] PLED has an advantage in terms of device fabrication as a
printing methodology may be adopted for soluble polymer
materials.
[0007] Although in the past twenty years OLED and PLED have shown
significant progress in their performance, there still remain
problems that need to be solved.
[0008] For instance, organic electroluminescent devices described
above still show insufficient performance in terms of durability
when used for a long time. The performance of organic
electroluminescent devices can be further improved by studying new
materials such as hole injection materials, hole transporting
materials, host materials, emission materials and some others.
Additionally, improvement of the device fabrication process is
required.
[0009] An important consideration to improving organic
electroluminescent device performance is to further decrease the
driving current within the device in order to enhance device
lifetimes. For example, some materials that address this concern
have been proposed (U.S. Pat. No. 6,436,559, JP 3571977, JP
3614405). Despite these advances in organic electroluminescent
devices using such materials, further improvements regarding
stability and the performance are still required.
SUMMARY OF THE INVENTION
[0010] The present invention either provides improvements to the
problems encountered in organic electroluminescent devices as
mentioned above, or provides a useful alternative. Specific
embodiments may provide an organic electroluminescent device with
high efficiency and longer life time. Specific embodiments may also
provide a stable device which has reduced current leakage at low
current range.
[0011] An organic electroluminescent device comprising: (i) an
anode; (ii) a cathode; and (ii) one or more layers arranged between
the anode and the cathode; wherein at least one of the one or more
layers is a light emitting layer and wherein the one or more
layers, comprises an organic compound represented by the
formula:
##STR00001##
wherein the substituents R.sub.1 and R.sub.2 are the same or
different and are selected from the group consisting of: (a)
hydrogen, (b) a substituted or unsubstituted heterocyclic group,
(c) a substituted or unsubstituted alkyl group, (d) a substituted
or unsubstituted aralkyl group, (e) a substituted aryl group
containing at least one atom selected from the group consisting of
N, O, S, Si, P, F, Cl, Br; and/or comprising at least three organic
rings, the organic rings being fused or non-fused, or (f) each of
R.sub.1 or R.sub.2 may together form a substituted or unsubstituted
cyclic group; and the substituents R.sub.3, R.sub.4, R.sub.5 and
R.sub.6 are the same or different and are each selected from the
group consisting of: hydrogen, deuterium, a substituted or
unsubstituted alkyl group, a halogen atom or a cyano group. In
certain embodiments, the compound represented by formula 1 is
suitable for use in an electroluminescent device as any one of an
electron transport layer, an emission layer, a host layer, a hole
transporting layer, or a hole injection layer.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 is a schematic illustration of a basic structure of
an organic electroluminescent device according to an embodiment of
the invention.
[0013] FIG. 2 is a schematic illustration of a basic structure of
an organic electroluminescent device according to another
embodiment of the invention.
[0014] FIG. 3 is a schematic illustration of a basic structure of
an organic electroluminescent device according to another
embodiment of the invention.
[0015] FIG. 4 is a schematic illustration of a basic structure of
an organic electroluminescent device according to another
embodiment of the invention.
[0016] FIG. 5 is a schematic illustration of a basic structure of
an organic electroluminescent device according to another
embodiment of the invention.
[0017] FIG. 6 is a schematic illustration of a basic structure of
an organic electroluminescent device according to another
embodiment of the invention.
DETAILED DESCRIPTION
[0018] The organic electroluminescent device according to the
present invention is composed of organic compounds layer(s) aligned
between an anode and a cathode. The layer(s) may comprise an
electron transport layer, an emission layer, a hole transporting
layer, a hole injection layer, and insulation layers. At least one
of these layers comprises a compound of formula 1.
[0019] The organic layer(s) may be constituted by (i) a single
layer doped with a compound of formula 1; or (ii) multiple layers
of which at least one layer may be doped with a compound of formula
1; or (iii) at least one layer is a layer comprised of a compound
of formula 1 doped with a separate dopant; or (iv) multiple layers
of which at least one layer may be comprised entirely of a compound
of formula 1. The situation where a particular layer comprises
primarily the compound of formula 1, and the layer is doped with at
least one dopant may also be referred to as a host-guest material.
In this situation, the compound of formula 1 is the host material
and the dopant is the guest material.
[0020] The term "compound" is used in its broadest sense to refer
to any chemical substance of formula 1.
[0021] The compounds of formula 1 have a biimidazole ring structure
and in particular a 2,2'-biimidazole structure. R.sub.1 and R.sub.2
are the same or different and are selected from the group
consisting of: hydrogen, a substituted or unsubstituted
heterocyclic group, a substituted or unsubstituted alkyl group, a
substituted or unsubstituted aralkyl group, a substituted aryl
group, or each of R.sub.1 or R.sub.2 may together form a
substituted or unsubstituted cyclic; and wherein the substituted
aryl group contains at least one atom selected from the group
consisting of N, O, S, Si, P, F, Cl, Br; and/or wherein the
substituted aryl group comprises at least three organic rings,
wherein the organic rings are fused or non-fused.
[0022] Where the substituted aryl group contains at least one atom
that is N, suitable substituents include: --NH.sub.2, --NHR,
--NRR', --N.dbd.R, --ONRR', --C(.dbd.NH)R, --C(.dbd.NR)R',
--C(.dbd.NH)H, --C(.dbd.NR)H, (RCO).sub.2N--, --N.sub.3,
--N.sub.2R, --OCN, --NCO, --ONO.sub.2, --CN, --NC, --ONO,
--NO.sub.2, --NO, --O.sub.5H.sub.4N.
[0023] Where the substituted aryl group contains at least one atom
that is O, suitable substituents include: --OH, --COR, --CHO, --COX
where X is a halide, --OCOOR, --COOH, --COOR, --OOH, --OOR, --OR,
--CH(OR)(OH), --C(OR')(OH)R, --CH(OR)(OR'), --C(OR')(OR'')R,
--C(OR)(OR')(OR''), --OC(OR)(OR')(OR'').
[0024] Where the substituted aryl group contains at least one atom
that is S, suitable substituents include: --SH, --SR, --SSR, --SOR,
--SO.sub.2R, --SO.sub.2H, --SO.sub.3H, --SCN, --NCS, --CSR,
--CSH.
[0025] Where the substituted aryl group contains at least one atom
that is Si, suitable substituents include: SiRR'R''
[0026] Where the substituted aryl group contains at least one atom
that is P, suitable substituents include: --PRR', --PORR', --PSRR',
--P(.dbd.O)(OH).sub.2, --OP(.dbd.O)(OH).sub.2, --OPO(OR)(OH),
--OPO(OR)(OR').
[0027] R, R', R'' are further substituents that may be the same or
different.
[0028] R.sub.3, R.sub.4, R.sub.5 and R.sub.6 are the same or
different and are each selected from the group consisting of:
hydrogen, deuterium, a substituted or unsubstituted alkyl group, a
halogen atom or a cyano group.
[0029] The term "aryl" is well understood in the art of chemistry,
and is used to refer to any aromatic substituent. The aryl group
may be carbocyclic (i.e. contain carbon and hydrogen only) or may
be heteroaromatic (i.e. contain carbon, hydrogen, and at least one
heteroatom). The aryl group may be monocyclic such as a phenyl, or
a polycyclic aryl group such as naphthyl or anthryl. Examples of
aryl groups include a phenyl group, biphenyl group, terphenyl
group, naphthyl group, anthryl group, pyrenyl group, etc.
[0030] The term "alkyl group" is well understood in the art of
chemistry. The alkyl group may be unsubstituted or substituted by a
suitable substituent. The alkyl group may be a linear or branched
alkyl group or cyclic alkyl group, preferably comprising of between
(and including) 1 and 20 carbon atoms. Examples of linear alkyl
groups include methyl, propyl or decyl, and examples of branched
alkyl groups include iso-butyl, tert-butyl or 3-methyl-hexyl.
Examples of cyclic alkyl groups include mono cyclohexyl and fused
alkyl cyclic ring systems.
[0031] The term "aralkyl" or "arylated alkyl" refers to an aryl
group which is substituted for the hydrogen atom of an alkyl
group.
[0032] The term "heterocyclic", and similarly "heterocyclic group"
or "heterocyclic ring" is well understood in the art of organic
chemistry, and is used to refer to any cyclic groups containing one
or more rings, such as between one and four rings, and between 5 to
50 (preferably 5 to 20) ring atoms, of which at least one atom is a
heteroatom. The heteroatoms may be selected from one or more of O,
N, S and Si. The heterocyclic group for the formula 1 may be a 5 or
6 membered heterocyclic ring comprising carbon atoms with one or
more of any of the following atoms: nitrogen, oxygen, sulphur and
silicon, such as pyrrolyl, thienyl, pyridyl or pyridazinyl. The
heterocyclic group may comprise a single heterocyclic ring, or more
than one linked or fused rings, with at least one ring containing a
heteroatom. One subclass of heterocyclic groups are the
heteroaromatic (or heteroaryl) groups, which are aromatic groups
containing one or more heteroatoms selected from one or more of O,
N and S. Such heteroaromatic groups also fall within the definition
of aryl group. Some specific examples for heterocyclic groups are
pyrrole, triazole, imidazole, pyrazole, 1,2,5-oxathiazole,
isoxazole, oxazole, furan, pyran, pyrone, thiazole, isothiazole,
pyrrolidine, pyrroline, imidazolidine, pyrazolidine. Other examples
include moieties of benzimidazole, thiophene, benzothiophene,
oxadiazoline, indoline, carbazole, pyridine, quinoline,
isoquinoline, benzoquinone, pyrazoline, imidazolidine, piperidine,
etc. The heterocyclic group may be monocyclic or polycyclic.
According to some embodiments, the heterocyclic group is
polycyclic. An example of a polycyclic heterocyclic group within
this class is carbazole.
[0033] In formula 1, the aryl, alkyl, aralkyl, or heterocyclic
group may additionally have one or more substituents selected from
any suitable substituents known in the art. Suitable substituents
may be selected from the group consisting of: halogen atom, nitro
group, carbonyl group, amide group, cyano group, carboxylate group,
sulfonate group, alkoxy group, aryloxy group, amino group,
alkylamino group, arylamino group, another aryl, alkyl or
heterocyclic group, in which each of the aryl, alkyl or
heterocyclic groups may be further substituted by one or more
further substituents. Thus, the further substituents on the aryl,
alkyl or heterocyclic group substituents may be selected from one
or more of a halogen atom, nitro group, carbonyl group, amide
group, cyano group, carboxylate group, sulfonate group, alkoxy
group, aryloxy group, amino group, alkylamino group and arylamino
group.
[0034] The substituents may be linked to the aryl, alkyl, aralkyl
or heterocyclic group directly by one atom or fused by more than
one atom or via a heteroatom such as nitrogen, oxygen, sulphur and
silicon. In some cases the substituent may be linked by two or more
points of attachment, as in the case of a divalent alkyl group, or
an ethylenedioxy group (i.e. --O--CH.sub.2CH.sub.2--O--).
[0035] The naming of ring systems and substituents is as per IUPAC
nomenclature.
[0036] Specific examples of the compound represented as formula 1
may include the examples shown below or shown in the examples, but
are not limited to these examples:
##STR00002## ##STR00003## ##STR00004## ##STR00005##
[0037] It is preferred that the compound represented as formula 1
has a melting point preferably between 150.degree. C. and
500.degree. C., and more preferably between 200.degree. C. and
400.degree. C.
[0038] As described above, the organic layer(s) may be constituted
by (i) a single layer doped with a compound of formula 1; or (ii)
multiple layers of which at least one layer may be doped with a
compound of formula 1; or (iii) at least one layer is a layer
comprised of a compound of formula 1 doped with at least one
dopant; or (iv) multiple layers of which at least one layer may be
comprised entirely of a compound of formula 1
[0039] In the organic luminescence device of the present
application, the organic compound layer comprising the
above-mentioned compound of the formula 1 may be formed separately,
or together, with the other layers (if any other layers are
present) between the pair of electrodes (cathode and anode).
Suitable formation techniques include vacuum deposition or solution
process.
[0040] The thickness of the organic compound layer may be
preferably less than at most 10 .mu.m, more preferably less than
0.5 .mu.m, even more preferably 0.001-0.5 .mu.m.
[0041] Specific embodiments of the invention will now be described
in further detail with reference to the accompanying figures, which
illustrate a range of possible arrangements for the device of the
present invention. It will be understood that these embodiments are
provided by way of example only, and are not intended to limit the
scope of the invention.
[0042] The electroluminescent device of embodiments of the present
application may have a single layer structure comprised of only
compound as defined by formula 1 as shown in FIG. 1 or be a
multiple layered structure of two or more layers as shown in FIGS.
2 and 3.
[0043] More specifically, FIG. 1 is a schematic cross section of a
first embodiment of the organic electroluminescent device of the
present invention. In FIG. 1, the organic electroluminescent device
includes a substrate 1, an anode 2 (deposited on the substrate 1),
an emission layer 3 (deposited on the anode 2) and a cathode 4
(deposited on the emission layer 3). In this embodiment, the
emission layer 3 forms a single organic compound type-layer. This
single layer may be composed entirely of a compound having hole
transporting ability, electron transporting ability and
luminescence ability (associated with the re-combination of
electrons and holes) based on its own properties, or through
combination with a dopant that enhances the performances of the
hole transporting ability, the electron transporting ability and
luminescence ability of the host compound. According to some
embodiments, the compound of formula 1 can serve as a host layer
with a dopant.
[0044] In FIG. 1, the emission layer 3 may preferably have a
thickness of 5 nm to 1 .mu.m, preferably 5 to 50 nm and more
preferably 30 to 45 nm.
[0045] FIG. 2 shows another embodiment of the organic
electroluminescent device of the present invention in the form of a
multiple layer-type device comprised of a hole transporting layer 5
and an electron transporting layer 6. Referring to FIG. 2, the
organic luminescent device includes a substrate 1, an anode 2
(deposited on the substrate 1), the hole transporting layer 5
(deposited on the anode 2), the electron transporting layer 6
(deposited on the hole transporting layer 5) and a cathode
(deposited on the electron transporting layer 6). In this
embodiment, either one or both of the hole transporting layer 5 and
the electron transporting layer 6 may contain an emissive compound
as dopant(s) for forming an emission layer 3. In this case, the
hole transporting layer 5 and the electron transporting layer 6 may
be comprised of non-luminescent compound(s), respectively. The
compound of formula 1 can form the hole transporting layer 5, or a
component of the hole transporting layer.
[0046] In the embodiment of FIG. 2, each of the hole transporting
layer 5 and the electron transporting layer 6 may have the
thickness of 5 nm to 1 .mu.m, more preferably 5 nm to 50 nm.
[0047] FIG. 3 shows another embodiment of the organic
electroluminescent device of the present invention in the form of a
multiple layer-type device comprising a hole transporting layer 5,
an emission layer 3, an electron transporting layer 6. In FIG. 3,
the organic luminescent device includes a substrate 1, an anode 2
(deposited on the substrate 1), the hole transporting layer 5
(deposited on the anode 2), the emission layer 3 (deposited on the
hole transporting layer 5), the electron transporting layer 6
(deposited on the emission layer 3) and a cathode (deposited on the
electron transporting layer 6). In this embodiment, each of the
hole transporting layer, the emission layer and the electron
transporting layer may be formed by use of a hole transporting
compound, an emissive compound (or an emissive compound and a host
compound) and an electron transporting compound, respectively or as
a mixture of these kinds of compounds. The compound of formula 1
can form the emission layer 3, or a component of the emission
layer.
[0048] FIG. 4 shows another embodiment of the organic
electroluminescent device of the present invention with multiple
layers comprising a hole injection layer 7, a hole transporting
layer 5, an emission layer 3 and an electron transporting layer 6.
In FIG. 4, the organic luminescent device includes a substrate 1,
an anode 2 (deposited on the substrate 1), the hole injection layer
7 (deposited on the anode 2), the hole transporting layer 5
(deposited on the hole injection layer), the emission layer 3
(deposited on the hole transporting layer 5), the electron
transporting layer 6 (deposited on the emission layer 3) and a
cathode (deposited on the electron transporting layer 6). In this
embodiment, each of the hole injection layer, the hole transporting
layer, the emission layer and the electron transporting layer may
be formed by use of a hole injection compound, a hole transporting
compound, an emissive compound (or an emissive compound and a host
compound) and an electron transporting compound, respectively or as
a mixture of these kinds of compounds. The compound of formula 1
can form the emission layer 3, or a component of the emission
layer.
[0049] FIG. 5 shows a further embodiment comprising layered
structure that includes a cathode, an electron injection layer, an
electron-transport layer, a hole-blocking layer, and emission (or
emissive) layer, a hole transport layer and an anode, and a
substrate layer. The anode is deposited on top of the glass
substrate, and each of the other layers is further deposited on a
preceding layer as shown in FIG. 5, with the top layer being the
cathode. In this particular figure, the cathode is aluminium with a
thickness of 100 nm, the electron-injection layer is LiF with a
thickness of 1 nm, the hole-blocking/electron transporting layer is
BCP (i.e. 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline) with a
thickness of 40 nm, the emission layer is a compound according to
formula 1 (i.e.
1,1-bis(9-phenyl-9H-carbazol-3-yl)-1H,1'H-2,2'-biimidazole) with a
thickness of 40 nm and doped at 8 wt % with Flrpic (i.e.
bis(4,6-difluorophenylpyridinato-N,C2)picolinatoiridium), the
hole-transporting layer is .alpha.-NPD (i.e. N,N'
bis(napthalen-1-yl)-N,N'-bis(phenyl)-2,2'-dimethylbenzidine) with a
thickness of 50 nm, the anode is ITO (i.e. indium tin oxide) with a
thickness of 150 nm. These layers are mounted on a glass
substrate.
[0050] FIG. 6 shows a further embodiment comprising layered
structure that includes a cathode, an electron injection layer, an
electron-transport layer, and emission (or emissive) layer, a hole
transport layer and an anode, and a substrate layer. The anode is
deposited on top of the glass substrate, and each of the other
layers is further deposited on a preceding layer as shown in FIG.
6, with the top layer being the cathode. In this particular figure,
the cathode is aluminium with a thickness of 100 nm, the
electron-injection layer is LiF with a thickness of 1 nm, the
electron transporting layer is TmPyPB (i.e.
1,3,5-tri[(3-pyridyl)-phen-3-yl]benzene) with a thickness of 40 nm,
the emission layer is a compound according to formula 1 (i.e.
1,1-bis(9-phenyl-9H-carbazol-3-yl)-1H,1'H-2,2'-biimidazole) with a
thickness of 40 nm and doped at 6 wt % with Flrpic (i.e.
bis(4,6-difluorophenylpyridinato-N, C2) picolinatoiridium), the
hole-transporting layer is TcTa (i.e.
4,4',4''-tris(carbazol-9-yl)triphenylamine) with a thickness of 70
nm, the anode is ITO (i.e. indium tin oxide) with a thickness of
145 nm. These layers are mounted on a glass substrate.
[0051] In FIGS. 1, 2, 3, 4, 5 and 6, each of the layers between the
anode and cathode may be formed by either vacuum deposition or wet
process using a low molecular weight compound or polymeric compound
or mixture of a low molecular weight compound and a polymeric
compound. Each thickness of the layers between the anode and
cathode may preferably be ranging from 1 nm to 1 .mu.m. Each of the
thickness of the cathode and the anode may be preferably 100-200
nm.
[0052] The organic layer structures in the devices shown in FIGS.
1, 2, 3, 4, 5 and 6 represent the basic structure, respectively, so
that the structure may be appropriately optimized depending on
characteristics demanded. Examples of suitable modifications
include the incorporation of one or more additional layers. For
example, the hole transporting layer may be altered to comprise a
hole injection layer (deposited on the anode) and hole transporting
layer (deposited on the hole injection layer).
[0053] The term electron-injection layer refers to a layer of
electron-injecting material. An electron-injecting material is one
that promotes the injection of electrons from the cathode and
through the electron-injection layer in the direction of cathode
toward the anode.
[0054] The term electron-transport layer refers to a layer
comprising an electron-transport material. An electron-transport
material is one which promotes the transport of electrons from the
cathode (or from the layer or layers in between the cathode and
electron-transporting layer) and through the electron-transporting
layer in the direction of cathode toward the anode.
[0055] The term hole-blocking layer refers to a layer comprising a
hole-blocking material. A hole-blocking material is one which
blocks the movement of "holes" from the emission layer (or from the
layer or layers in between the emission layer and hole-blocking
layer) in the direction of anode toward the cathode. Additionally,
the hole-blocking material should be able to function as an
electron-transporting material.
[0056] The term "emission layer" or "emissive layer" refers to the
layer from which light is emitted. The recombination of holes and
electrons within this layer produces light. The emission layer is
comprised of at least one emissive material (or emitter). In some
instances an emission layer may comprise a host material with an
emitter or emitters. The term "guest" or "dopant" is also used to
describe an emitter.
[0057] The term "electron-blocking layer" refers to a layer
comprising an electron-blocking material. An electron-blocking
material is one which blocks the movement of electrons from the
emission layer (or from the layer or layers in between the emission
layer and electron-blocking layer) in the direction of cathode
toward the anode. Additionally, the electron-blocking material
should be able to function as a hole-transporting material.
[0058] The term hole-transporting layer refers to a layer
comprising a hole-transporting material. A hole-transport material
is one which promotes the transport of holes from the anode (or
from the layer or layers in between the anode and hole-transporting
layer) and through the hole-transporting layer in the direction of
anode toward the cathode.
[0059] The term hole-injection layer refers to a layer of
hole-injecting material. A hole-injecting material is one that
promotes the injection of holes from the anode and through the
hole-injection layer in the direction of anode toward the
cathode.
[0060] More specific embodiments of the device structure other than
those of FIGS. 1, 2, 3, 4, 5 and 6 are shown below, but not
restricted to these device structures.
(1) Anode/hole transporting layer/emission layer/electron
transporting layer/electron injection layer/cathode (2) Anode/hole
injection layer/emission layer/electron transporting layer/electron
injection layer/cathode (3) Anode/insulating layer/hole
transporting layer/emission layer/electron transporting
layer/cathode (4) Anode/hole transporting layer/emission
layer/electron transporting layer/insulating layer/cathode (5)
Anode/inorganic semiconductor/insulator/hole transporting
layer/emission layer/insulator/cathode (6) Anode/insulating
layer/hole transporting layer/emission layer/electron transporting
layer/insulating layer/cathode (7) Anode/insulating layer/hole
injection layer/hole transporting layer/emission layer/electron
transporting layer/electron injection layer/cathode (8)
Anode/insulating layer/hole injection layer/hole transporting
layer/emission layer/electron transporting layer/electron injection
layer/insulating layer/cathode
[0061] In the embodiments described above, more preferable device
structures are (1), (2), (3), (7) and (8), although this is not a
restriction. Furthermore, a hole blocking layer may be present
between the emissive layer and the electron transport layer in any
of the embodiments listed above, or in FIGS. 3 and 4.
[0062] The electron injection layer has a thickness of 1 nm to 1
.mu.m, more preferably 1-50 nm. The electron transport layer has a
thickness of 1 nm to 1 .mu.m, preferably 1-50 nm and more
preferably 25-35 nm. The hole blocking layer has a thickness of 1
to 50 nm, preferably 1 to 20 nm and most preferably about 10 nm.
The emissive layer has a thickness of 5 nm to 1 .mu.m, preferably 5
to 50 nm and more preferably 30 to 45 nm. The hole transport layer
has a thickness of 1 nm to 1 .mu.m, more preferably 1-50 nm. The
hole injection layer has a thickness of 1 nm to 1 .mu.m, more
preferably 1-50 nm.
[0063] According to some embodiments, the compound of the formula 1
may be formed as a hole injection layer, hole generation layer or
hole transport layer. According to some embodiments, there is
provided the use of the compound of formula 1 as a hole injection
material, hole generation material, or hole transport material as a
hole injection layer, a hole generation layer, a hole transporting
material, or as a dopant in a hole transporting layer.
[0064] According to other embodiments, the compound of the formula
1 may be formed as an electron injection layer, electron generation
layer or electron transport layer. According to some embodiments,
there is provided the use of the compound of formula 1 as an
electron injection material, electron generation material, or
electron transport material as an electron injection layer, an
electron generation layer, an electron transporting material, or as
a dopant in an electron transporting layer.
[0065] In some embodiments, the compound of the formula 1 may be
used in combination with a hole transporting compound (or
material), an electron transporting compound and/or an emission
compound. The situation where the compound of formula 1 is used in
conjunction with a dopant is also referred to as a host-guest
complex. In this situation the organic compound is present as the
host or the matrix phase, and it contains a dopant or guest
molecule dispersed throughout.
[0066] Examples of suitable dopants or guest materials are
dependent on whether the organic compound of formula 1 is being
used as a hole transporting material, an electron transporting
material, or an emissive material. Suitable dopants or guest
materials are not limited to, but may include the following:
Hole Transporting Materials/Compounds:
##STR00006## ##STR00007## ##STR00008##
[0067] Electron Transporting Materials/Compounds:
##STR00009##
[0068] Emission Materials/Compounds:
##STR00010## ##STR00011##
[0070] When the compound of formula 1 is used as a host in the
emission layer, the dopant or guest compound is present in an
amount between 1 and 50 wt %, preferably between 1 and 20 wt %,
more preferably between 5 and 12 wt % and most preferably at about
8 wt %. In a preferred embodiment the dopant or guest material is a
phosphorescent or fluorescent material. In the case where the
dopant or guest material is a phosphorescent material, it is
preferred that the dopant further comprises an iridium, osmium,
platinum, rhodium, ruthenium, or palladium constituent
[0071] As a material for the anode (e.g. 2 in FIGS. 1-4), it is
preferred to use one having a large work function, examples of
which may include metals, such as gold, platinum, nickel,
palladium, cobalt, selenium, vanadium and their alloys; metal
oxides, such as tin oxide, zinc oxide, indium zinc oxide (IZO) and
indium tin oxide (ITO) and electroconductive polymers, such as
polyaniline, polypyrole and polythiophene and derivatives thereof.
These compounds may be used singly or in combination of two or more
species.
[0072] As a material for the cathode (e.g. 4 in FIGS. 1-4), it is
preferred to use one having a smaller work function, usually under
4.0 eV, examples of which may include; metals such as sodium,
magnesium, lithium, potassium, aluminium, indium, silver, lead,
chromium and their alloys, or oxides. In the case of metal oxide,
those such as indium oxide (ITO), indium zinc oxide (IZO) and zinc
oxide are suitable.
[0073] The insulating layer may be deposited adjacent to either
electrode to avoid current leakage as mentioned in embodiments (3)
to (8). As the insulating material, it is preferred to use an
inorganic compound, examples of which may include aluminium oxide,
lithium fluoride, lithium oxide, caesium oxide, magnesium oxide,
magnesium fluoride, calcium oxide, calcium fluoride, aluminium
nitride, titanium oxide, silicon oxide, silicon nitride, boron
nitride, vanadium oxide.
[0074] The substrate (e.g., 1 shown in FIGS. 1 to 4) for the
organic electroluminescence device of the present invention may
include an opaque substrate made from any suitable material, such
as metal or ceramics, or a transparent substrate made from any
suitable transparent material such as glass, quartz, plastics, etc.
It is possible to form the substrate with a colour filter film, a
fluorescent colour conversion film, dielectric reflection film,
etc., thus controlling such aspects of the emitted luminescent
light.
[0075] The devices of the present application can be provided in
the form of a stacked organic electroluminescent (EL) device. The
stacked organic EL device may contain a number of stacked emission
layers, wherein each emission layer can comprise multiple emitters.
In one embodiment, the stacked EL device is for emission of white
light and contains three stacked emission layers, each layer
containing a different single emitter. In another embodiment, the
stacked EL device is for white emission and contains two stacked
emission layers wherein at least one of the layers contains two
emitters.
[0076] The present application also extends to electronic devices
comprising the organic electroluminescent device of the present
invention, including displays and light sources.
[0077] The present invention will be described below in detail with
preparation examples and the device examples, but the present
invention is not intended to be restricted to these examples.
[0078] As used herein, except where the context requires otherwise,
the term "comprise" and variations of the term, such as
"comprising", "comprises" and "comprised", are not intended to
exclude other additives, components, integers or steps.
[0079] Reference to any prior art in the specification is not, and
should not be taken as, an acknowledgment, or any form of
suggestion, that this prior art forms part of the common general
knowledge in any other jurisdiction or that this prior art could
reasonably be expected to be ascertained, understood and regarded
as relevant by a person skilled in the art.
[0080] Recitation of ranges of values herein are merely intended to
serve as a shorthand method of referring individually to each
separate value and each potential range encompassed within said
range, unless otherwise stated. Furthermore, each separate value
and each potential range is incorporated into the specification as
if it were individually recited herein.
EXAMPLES
Synthetic Example 1
1,1'-bis(9-phenyl-9H-carbazol-3-yl)-1H,1'H-2,2'-biimidazole
##STR00012##
[0082] A mixture of 1H,1'H-2,2'-biimidazole (600 mg, 4.48 mmol),
3-bromo-9-phenyl-9H-carbazole (5.79 g, 18.0 mmol) and
Cs.sub.2CO.sub.3 (6.13 g, 18.9 mmol) in DMF (120 mL) was degassed
(N.sub.2 bubbling, 15 min). Cu.sub.2O (260 mg, 1.8 mmol) was added
and the mixture was heated (140.degree. C., 72 h). The mixture was
allowed to cool to room temperature and filtered through Celite
washing with CH.sub.2Cl.sub.2. The combined filtrate and washings
were concentrated. The mixture was diluted with CH.sub.2Cl.sub.2
and H.sub.2O and the organic phase was separated. The aqueous phase
was re-extracted (CH.sub.2Cl.sub.2) and the combined organics were
washed (saturated aqueous NaCl), dried (MgSO.sub.4), filtered and
concentrated to give a solid residue. The residue was purified by
flash chromatography (EtOAc/CH.sub.2Cl.sub.2/MeOH 40:60:0 then
40:60:3 then 40:60:5) to give
1,1'-bis(9-phenyl-9H-carbazol-3-yl)-1H,1H-2,2'-biimidazole (980 mg,
36%) as a colourless solid. A portion of this material was further
purified firstly, by recrystallisation
(CH.sub.2Cl.sub.2/toluene/petrol) and then by sublimation
(230.degree. C., 10.sup.-6 mBar): m.p. 235-242.degree. C. (DSC);
.sup.1H NMR (CDCl.sub.3, 400 MHz) .delta. 6.76 (dd, J 2.1, 8.6 Hz,
2H), 7.06-7.01 (m, 4H), 7.14 (ddd, J 1.4, 6.8, 8.0 Hz, 2H),
7.22-7.38 (m, 8H), 7.42-7.50 (m, 6H), 7.55-7.61 (m, 4H), 7.68-7.72
(m, 2H); .sup.13C NMR (CDCl.sub.3, 100 MHz) .delta. 109.9, 110.1,
116.2, 120.2, 120.5, 122.0, 122.1, 123.5, 126.8, 126.9, 127.9,
128.6, 130.0, 135.4, 136.8, 139.8, 141.4; HRMS (EI) m/z 616.2350
C.sub.42H.sub.28N.sub.6 [M].sup.+.cndot. requires 616.2370.
Synthetic Example 2
4,4'-(1H,1'H-2,2'-biimidazole-1,1'-diyl)bis(N,N-diphenylaniline)
##STR00013##
[0084] A mixture of 1H,1'H-2,2'-biimidazole (1.02 g, 7.63 mmol),
4-bromo-N,N-diphenylaniline (9.89 g, 30.5 mmol) and
Cs.sub.2CO.sub.3 (12.4 g, 38.2 mmol) in DMF (150 mL) was degassed
(N.sub.2 bubbling, 15 min). Cu.sub.2O (440 mg, 3.0 mmol) was added
and the mixture was heated (140.degree. C., 72 h). The mixture was
allowed to cool to room temperature and filtered through Celite
washing with CH.sub.2Cl.sub.2. The combined filtrate and washings
were concentrated. The mixture was diluted with CH.sub.2Cl.sub.2
and H.sub.2O and the organic phase was separated. The aqueous phase
was re-extracted (CH.sub.2Cl.sub.2) and the combined organics were
washed (saturated aqueous NaCl), dried (MgSO.sub.4), filtered and
concentrated to give a solid residue. The residue was purified by
flash chromatography (EtOAc/Et.sub.3N/MeOH 100:1:0 then 100:1:2
then 100:1:5) to give
4,4'-(1H,1H-2,2'-biimidazole-1,1'-diyl)bis(N,N-diphenylaniline)
(1.57 g, 33%) as a colourless solid. A portion of this material was
further purified firstly, by recrystallisation (petrol/toluene) and
then by distillation (sublimation apparatus 215.degree. C., mBar):
m.p. 174-182.degree. C. (DSC); .sup.1H NMR (CDCl.sub.3, 400 MHz)
.delta. 6.67 (d, J 8.8 Hz, 4H), 6.88 (d, J 8.8 Hz, 4H), 7.00-7.06
(m, 12H), 7.15 (br s, 2H), 7.18-7.25 (m, 8H), 7.34 (br s, 2H);
.sup.13C NMR (CDCl.sub.3, 100 MHz) .delta. 121.8, 122.7, 123.8,
124.6, 124.7, 128.9, 129.4, 130.0, 146.9, 147.8; HRMS (EI) m/z
619.2598 C.sub.42H.sub.31N.sub.6 [M-H].sup.+.cndot. requires
619.2605.
Synthetic Example 3
1,1'-bis(4-(9H-carbazol-9-yl)phenyl)-1H,1'H-2,2'-biimidazole
##STR00014##
[0086] A mixture of 1H,1'H-2,2'-biimidazole (610 mg, 4.5 mmol),
3-bromo-9-phenyl-9H-carbazole (5.1 g, 15.8 mmol) and
Cs.sub.2CO.sub.3 (6.62 g, 20.4 mmol) in DMF (100 mL) was degassed
(N.sub.2 bubbling, 15 min). Cu.sub.2O (260 mg, 1.8 mmol) was added
and the mixture was heated (140.degree. C., 72 h). The mixture was
allowed to cool to room temperature and filtered through Celite
washing with CH.sub.2Cl.sub.2. The combined filtrate and washings
were concentrated. The mixture was diluted with CH.sub.2Cl.sub.2
and H.sub.2O and the organic phase was separated. The aqueous phase
was re-extracted (CH.sub.2Cl.sub.2) and the combined organics were
washed (saturated aqueous NaCl), dried (MgSO.sub.4), filtered and
concentrated to give a solid residue. The residue was purified by
flash chromatography (EtOAc/CH.sub.2Cl.sub.2/MeOH 40:60:0 then
40:60:2 then 40:60:4) to give
1,1'-bis(4-(9H-carbazol-9-yl)phenyl)-1H,1'H-2,2'-biimidazole (1.13
g, 41%) as a colourless solid. A portion of this material was
further purified firstly, by recrystallisation
(CH.sub.2Cl.sub.2/toluene) and then by distillation (sublimation
apparatus 300.degree. C., 10.sup.-6 mBar): m.p. 270-274.degree. C.
(DSC); .sup.1H NMR (CDCl.sub.3, 400 MHz) .delta. 7.17 (d, J 8.7 Hz,
4H), 7.25-7.39 (m, 10H), 7.42 (br s, 2H), 7.50 (d, J 8.7 Hz, 4H),
8.13 (dd, J 1.4, 7.7 Hz, 4H); .sup.13C NMR (CDCl.sub.3, 100 MHz)
.delta. 109.3, 120.5, 120.5, 121.4, 123.6, 125.3, 126.1, 127.5,
130.6, 135.8, 137.2, 140.3; HRMS (EI) m/z 616.2347
C.sub.42H.sub.28N.sub.6 [M].sup.+.cndot. requires 616.2370.
Synthetic Example 4
1,1'-bis(9-(pyridin-2-yl)-9H-carbazol-3-yl)-1H,1'H-2,2'-biimidazole
##STR00015##
[0088] A mixture of 1H, 1'H-2,2'-biimidazole (800 mg, 6.0 mmol),
3-bromo-9-(pyridin-2-yl)-9H-carbazole (6.7 g, 20.8 mmol) and
Cs.sub.2CO.sub.3 (9.66 g, 29.7 mmol) in DMF (100 mL) was degassed
(N.sub.2 bubbling, 15 min). Cu.sub.2O (340 mg, 2.4 mmol) was added
and the mixture was heated (140.degree. C., 72 h). The mixture was
allowed to cool to room temperature and filtered through Celite
washing with CH.sub.2Cl.sub.2. The combined filtrate and washings
were concentrated. The mixture was diluted with CH.sub.2Cl.sub.2
and H.sub.2O and the organic phase was separated. The aqueous phase
was re-extracted (CH.sub.2Cl.sub.2) and the combined organics were
washed (saturated aqueous NaCl), dried (MgSO.sub.4), filtered and
concentrated to give a solid residue. The residue was purified by
flash chromatography (EtOAc/CH.sub.2Cl.sub.2/MeOH 40:60:0 then
40:60:3 then 40:60:5) to give
1,1'-bis(9-(pyridin-2-yl)-9H-carbazol-3-yl)-1H,1'H-2,2'-biimidazole
(1.44 g, 39%) as a colourless solid. A portion of this material was
further purified firstly, by recrystallisation
(CH.sub.2Cl.sub.2/toluene/petrol) and then by distillation
(sublimation apparatus 280.degree. C., 10.sup.-6 mBar): m.p.
215-227.degree. C. (DSC); .sup.1H NMR (CDCl.sub.3, 400 MHz) .delta.
6.78 (dd, J 2.1, 8.7 Hz, 2H), 7.02-7.12 (m, 4H), 7.18 (d, J 1.9 Hz,
2H), 7.28-7.34 (m, 6H), 7.47 (d, J 8.1 Hz, 2H), 7.54 (d, J 8.7 Hz,
2H), 7.60 (d, J 7.5 Hz, 2H), 7.66 (d, J 8.3 Hz, 2H), 7.88 (dt J
2.0, 7.5 Hz, 2H), 8.69 (ddd, J 0.7, 1.9, 4.9 Hz, 2H); .sup.13C NMR
(CDCl.sub.3, 50 MHz) .delta. 111.0, 111.3, 115.9, 118.8, 120.0,
121.0, 121.4, 122.4, 123.2, 124.4, 126.7, 129.8, 130.7, 138.1,
138.5, 139.8, 149.6, 151.2; HRMS (EI) m/z 617.2175
C.sub.40H.sub.25N.sub.8 [M-H].sup.+.cndot. requires 616.2197.
Synthetic Example 5
1,1'-di(9,9'-spirobi[fluorene]-2-yl)-1H,1'H-2,2'-biimidazole
##STR00016##
[0090] A mixture of 1H,1'H-2,2'-biimidazole (340 mg, 2.5 mmol),
2-bromo-9,9'-spirobi(fluorene) (3.2 g, 8.1 mmol) and
Cs.sub.2CO.sub.3 (4.12 g, 12.6 mmol) in DMF (60 mL) was degassed
(N.sub.2 bubbling, 15 min). Cu.sub.2O (140 mg, 0.98 mmol) was added
and the mixture was heated (140.degree. C., 72 h). The mixture was
allowed to cool to room temperature and filtered through Celite
washing with CH.sub.2Cl.sub.2. The combined filtrate and washings
were concentrated. The mixture was diluted with CH.sub.2Cl.sub.2
and H.sub.2O and the organic phase was separated. The aqueous phase
was re-extracted (CH.sub.2Cl.sub.2) and the combined organics were
washed (saturated aqueous NaCl), dried (MgSO.sub.4), filtered and
concentrated to give a solid residue. The residue was purified by
flash chromatography (EtOAc/CH.sub.2Cl.sub.2/MeOH 40:60:0 then
40:60:2 then 40:60:4) to give
1,1'-di(9,9'-spirobi[fluorene]-2-yl)-1H,1'H-2,2'-biimidazole (560
mg, 29%) as a colourless solid. A portion of this material was
further purified firstly, by recrystallisation
(CH.sub.2Cl.sub.2/toluene) and then by sublimation (320.degree. C.,
10.sup.-6 mBar): m.p. 404-412.degree. C. (DSC); .sup.1H NMR
(CDCl.sub.3, 400 MHz) .delta. 5.84 (d, J 1.9 Hz, 2H), 6.33 (d, J
7.6 Hz, 4H), 6.60 (s, 2H), 6.64-6.71 (m, 4H), 6.84 (s, 2H), 6.92
(t, J 7.4 Hz, 4H), 7.14 (t, J 7.4 Hz, 2H), 7.25 (t, J 7.5 Hz, 4H),
7.40 (t, J 7.4 Hz, 2H), 7.49 (d, J 8.2 Hz, 2H), 7.72-7.80 (m, 6H);
.sup.13C NMR (CDCl.sub.3, 100 MHz) .delta. 65.6, 118.2, 120.1,
120.1, 120.2, 120.3, 122.1, 123.8, 124.2, 127.8, 127.9, 128.2,
129.3, 136.0, 136.5, 140.4, 140.6, 141.6, 147.7, 148.8, 150.0; HRMS
(EI) m/z 761.2662 C.sub.56H.sub.33N.sub.4 [M-H].sup.+.cndot.
requires 761.2700.
Synthetic Example 6
1,1'-bis(4-(pyridin-3-yl)phenyl)-1H,1'H-2,2'-biimidazole
##STR00017##
[0092] A mixture of 1H,1'H-2,2'-biimidazole (950 mg, 7.1 mmol),
3-(4-bromophenyl)pyridine (4.95 g, 21.3 mmol) and Cs.sub.2CO.sub.3
(9.24 g, 28.4 mmol) in DMF (80 mL) was degassed (N.sub.2 bubbling,
15 min). Cu.sub.2O (410 mg, 2.9 mmol) was added and the mixture was
heated (140.degree. C., 72 h). The mixture was allowed to cool to
room temperature and filtered through Celite washing with
CH.sub.2Cl.sub.2. The combined filtrate and washings were
concentrated. The mixture was diluted with CH.sub.2Cl.sub.2 and
H.sub.2O and the organic phase was separated. The aqueous phase was
re-extracted (CH.sub.2Cl.sub.2) and the combined organics were
washed (saturated aqueous NaCl), dried (MgSO.sub.4), filtered and
concentrated to give a solid residue. The residue was purified by
flash chromatography (EtOAc/CH.sub.2Cl.sub.2/MeOH 40:60:3 then
35:60:5 then 30:60:10) to give
1,1'-bis(4-(pyridin-3-yl)phenyl)-1H,1H-2,2'-biimidazole (1.05 g,
34%) as a colourless solid. A portion of this material was further
purified firstly, by recrystallisation
(CH.sub.2Cl.sub.2/toluene/petrol) and then by distillation
(sublimation apparatus 260.degree. C., 10.sup.-6 mBar): m.p.
218-223.degree. C. (DSC); .sup.1H NMR (CDCl.sub.3, 400 MHz) .delta.
6.95-7.00 (m, 4H), 7.15 (d, J 1.2 Hz, 2H), 7.29 (d, J 1.2 Hz, 2H),
7.38 (ddd, J 0.6, 4.8, 7.9 Hz, 2H), 7.40-7.45 (m, 4H), 7.82 (ddd, J
0.6, 1.7, 7.9 Hz, 2H), 8.62 (dd, J 1.4, 4.8 Hz, 2H), 8.79 (d, J 1.9
Hz, 2H); .sup.13C NMR (CDCl.sub.3, 100 MHz) .delta. 121.4, 123.7,
124.8, 127.7, 130.2, 134.1, 135.2, 137.0, 137.2, 137.3, 148.1,
149.0; HRMS (EI) m/z 439.1665 C.sub.28H.sub.19N.sub.6
[M-H].sup.+.cndot. requires 439.1666.
Synthetic Example 7
N,N'-(4,4'-(1H,
1'H-2,2'-biimidazole-1,1'-diyl)bis(4,1-phenylene))bis(N-(pyridin-2-yl)pyr-
idin-2-amine)
##STR00018##
[0094] A mixture of 1H,1'H-2,2'-biimidazole (840 mg, 6.3 mmol),
N-(4-bromophenyl)-N-(pyridin-2-yl)pyridin-2-amine (6.59 g, 20.3
mmol) and Cs.sub.2CO.sub.3 (10.14 g, 31.2 mmol) in DMF (70 mL) was
degassed (N.sub.2 bubbling, 15 min). Cu.sub.2O (360 mg, 2.5 mmol)
was added and the mixture was heated (140.degree. C., 72 h). The
mixture was allowed to cool to room temperature and filtered
through Celite washing with CH.sub.2Cl.sub.2. The combined filtrate
and washings were concentrated. The mixture was diluted with
CH.sub.2Cl.sub.2 and H.sub.2O and the organic phase was separated.
The aqueous phase was re-extracted (CH.sub.2Cl.sub.2) and the
combined organics were washed (saturated aqueous NaCl), dried
(MgSO.sub.4), filtered and concentrated to give a solid residue.
The residue was purified by flash chromatography
(EtOAc/CH.sub.2Cl.sub.2/MeOH 35:60:5 then 32:60:8 then 28:60:12) to
give
N,N'-(4,4'-(1H,1'H-2,2'-biimidazole-1,1'-diyl)bis(4,1-phenylene))bis(N-(p-
yridin-2-yl)pyridin-2-amine) (1.36 g, 35%) as a colourless solid. A
portion of this material was further purified firstly, by
recrystallisation (CH.sub.2Cl.sub.2/EtOAc/petrol) and then by
distillation (sublimation apparatus 260.degree. C., 10.sup.-6
mBar): m.p. 218-222.degree. C. (DSC); .sup.1H NMR (CDCl.sub.3, 400
MHz) .delta. 6.75-6.80 (m, 4H), 6.90 (ddd, J 0.8, 4.9, 7.3 Hz, 4H),
6.93-7.00 (m, 8H), 7.09 (d, J 1.0 Hz, 2H), 7.26 (s, 2H), 7.52 (ddd,
J 2.0, 7.3, 8.3 Hz, 4H), 8.24 (ddd, J 0.7, 1.9, 4.9 Hz, 4H);
.sup.13C NMR (CDCl.sub.3, 100 MHz) .delta. 117.0, 118.6, 121.1,
125.2, 127.5, 130.0, 133.7, 137.6, 144.3, 148.6, 157.7; HRMS (EI)
m/z 623.2420 C.sub.38H.sub.27N.sub.10 [M-H].sup.+.cndot. requires
623.2415.
Synthetic Example 8
1,1'-bis(4-(10H-phenothiazin-10-yl)phenyl)-1H,1'H-2,2'-biimidazole
##STR00019##
[0096] A mixture of 1H,1'H-2,2'-biimidazole (480 mg, 3.6 mmol),
10-(4-bromophenyl)-10H-phenothiazine (3.80 g, 10.8 mmol) and
Cs.sub.2CO.sub.3 (5.85 g, 18.0 mmol) in DMF (60 mL) was degassed
(N.sub.2 bubbling, 15 min). Cu.sub.2O (210 mg, 1.5 mmol) was added
and the mixture was heated (140.degree. C., 72 h). The mixture was
allowed to cool to room temperature and filtered through Celite
washing with CH.sub.2Cl.sub.2. The combined filtrate and washings
were concentrated. The mixture was diluted with CH.sub.2Cl.sub.2
and H.sub.2O and the organic phase was separated. The aqueous phase
was re-extracted (CH.sub.2Cl.sub.2) and the combined organics were
washed (saturated aqueous NaCl), dried (MgSO.sub.4), filtered and
concentrated to give a solid residue. The residue was purified by
flash chromatography (EtOAc/CH.sub.2Cl.sub.2/MeOH 40:60:0 then
38:60:2 then 35:60:5) to give
1,1'-bis(4-(10H-phenothiazin-10-yl)phenyl)-1H,1'H-2,2'-biimidazole
(1.12 g, 46%) as a colourless solid. A portion of this material was
further purified firstly, by recrystallisation
(CH.sub.2Cl.sub.2/toluene/petrol) and then by distillation
(sublimation apparatus 260.degree. C., 10.sup.-6 mBar): m.p.
227-232.degree. C. (DSC); .sup.1H NMR (CDCl.sub.3, 400 MHz) .delta.
6.36-6.42 (m, 4H), 6.86-6.97 (m, 12H), 7.08-7.16 (m, 8H), 7.20 (br
s, 2H), 7.35 (br s, 2H); .sup.13C NMR (CDCl.sub.3, 100 MHz) .delta.
118.4, 123.6, 123.8, 125.4, 126.8, 127.4, 128.4, 130.5, 135.2,
141.5, 143.3; HRMS (EI) m/z 679.1710 C.sub.42H.sub.27N.sub.6S.sub.2
[M-H].sup.+.cndot. requires 679.1733.
Synthetic Example 9
3,3'-(4,4'-dimethyl-1H,1'H-2,2'-biimidazole-1,1'-diyl)bis(9-phenyl-9H-carb-
azole)
##STR00020##
[0098] A mixture of
3-(2-iodo-4-methyl-1H-imidazol-1-yl)-9-phenyl-9H-carbazole (5.27 g,
11.7 mmol), 1,10-phenanthroline (2.11 g, 11.7 mmol) and
Cs.sub.2CO.sub.3 (7.63 g, 23.5 mmol) in DMF (60 mL) was degassed
(N.sub.2 bubbling, 15 min). CuI (2.23 g, 11.7 mmol) was added and
the mixture was heated (140.degree. C., 24 h). The mixture was
allowed to cool to room temperature and filtered through Celite
washing with CH.sub.2Cl.sub.2. The combined filtrate and washings
were concentrated. The mixture was diluted with CH.sub.2Cl.sub.2
and H.sub.2O and the organic phase was separated. The aqueous phase
was re-extracted (CH.sub.2Cl.sub.2) and the combined organics were
washed (saturated aqueous NaCl), dried (MgSO.sub.4), filtered and
concentrated to give a solid residue. The residue was purified by
flash chromatography, firstly, (EtOAc/CH.sub.2Cl.sub.2/MeOH 49:60:1
then 37:60:3 then 34:60:6) and secondly, (EtOAc/MeOH 94:6) to give
3,3'-(4,4'-dimethyl-1H,
1'H-2,2'-biimidazole-1,1'-diyl)bis(9-phenyl-9H-carbazole) (2 g,
53%) as a colourless solid. A portion of this material was further
purified firstly, by recrystallisation (EtOAc/petrol) and then by
distillation (sublimation apparatus 280.degree. C., 10.sup.-6
mBar): m.p. 245-253.degree. C. (DSC); .sup.1H NMR (CDCl.sub.3, 400
MHz) .delta. 2.37 (d, J 0.7 Hz, 6H), 6.67 (dd, 2.1, 8.6 Hz, 2H),
6.78 (d, J 0.9 Hz, 2H), 7.01 (d, J 8.6 Hz, 2H), 7.10 (dt, J 1.2,
7.0 Hz, 2H), 7.14 (d, J 1.9 Hz, 2H), 7.23-7.33 (m, 4H), 7.35-7.40
(m, 4H), 7.46 (tt, J 1.2, 6.7 Hz, 2H), 7.53-7.59 (m, 4H), 7.61 (d,
J, 7.8 Hz, 2H); .sup.13C NMR (CDCl.sub.3, 100 MHz) .delta. 13.7,
109.4, 109.8, 115.6, 118.2, 119.8, 120.0, 122.0, 122.4, 123.3,
126.4, 126.7, 127.6, 129.9, 130.2, 137.2, 137.4, 138.8, 139.0,
141.1; HRMS (EI) m/z 644.2664 C.sub.44H.sub.32N.sub.6
[M].sup.+.cndot. requires 644.2683.
Synthetic Example 10
1,1'-bis(6-methyl-9-p-tolyl-9H-carbazol-3-yl)-1H,1'H-2,2'-biimidazole
##STR00021##
[0100] A mixture of 1H,1'H-2,2'-biimidazole (890 mg, 6.6 mmol),
3-bromo-6-methyl-9-p-tolyl-9H-carbazole (6.49 g, 18.6 mmol) and
Cs.sub.2CO.sub.3 (7.55 g, 23.2 mmol) in DMF (80 mL) was degassed
(N.sub.2 bubbling, 15 min). Cu.sub.2O (380 mg, 2.7 mmol) was added
and the mixture was heated (140.degree. C., 96 h). The mixture was
allowed to cool to room temperature and filtered through Celite
washing with CH.sub.2Cl.sub.2. The combined filtrate and washings
were concentrated. The mixture was diluted with CH.sub.2Cl.sub.2
and H.sub.2O and the organic phase was separated. The aqueous phase
was re-extracted (CH.sub.2Cl.sub.2) and the combined organics were
washed (saturated aqueous NaCl), dried (MgSO.sub.4), filtered and
concentrated to give a solid residue. The residue was purified by
flash chromatography (EtOAc/CH.sub.2Cl.sub.2/MeOH 39:60:1 then
37:60:3 then 35:60:5) to give
1,1'-bis(6-methyl-9-p-tolyl-9H-carbazol-3-yl)-1H,1'H-2,2'-biimidazole
(1.42 g, 32%) as a colourless solid. A portion of this material was
further purified firstly, by recrystallisation
(CH.sub.2Cl.sub.2/toluene/petrol) and then by distillation
(sublimation apparatus 270.degree. C., 10.sup.-6 mBar): m.p.
208-214.degree. C. (DSC); .sup.1H NMR (CDCl.sub.3, 400 MHz) .delta.
2.38 (s, 6H), 2.49 (s, 6H), 6.71 (dd, J 1.8, 8.7 Hz, 2H), 7.03 (d,
J 8.6 Hz, 2H), 7.05-7.20 (m, 8H), 7.23-7.40 (m, 12H); .sup.13C NMR
(CDCl.sub.3, 100 MHz) .delta. 21.2, 21.3, 109.4, 109.4, 115.7,
119.7, 121.8, 122.4, 123.1, 126.5, 127.8, 129.3, 129.6, 130.4,
134.6, 137.4, 139.6, 139.7; HRMS (EI) m/z 671.2916
C.sub.46H.sub.35N.sub.6 [M-H].sup.+.cndot. requires 671.2918.
Synthetic Example 11
1,1'-bis(4-bromobenzyl)-1H,1'H-2,2'-biimidazole
##STR00022##
[0102] To a mixture of 1H,1'H-2,2'-biimidazole (2.1 g, 15.7 mmol)
in DMF at 0.degree. C. was added NaH (1.32 g of a 60% dispersion in
mineral oil, 32.8 mmol). The mixture was allowed to warm to room
temperature and stirred for 30 min. 1-bromo-4-(bromomethyl)benzene
(11.7 g, 46.8 mmol) was added and the mixture was heated to
80.degree. C. and stirred (2 h). The mixture was cooled to room
temperature and saturated aqueous NH.sub.4Cl (2 mL) was added and
the mixture was concentrated. The mixture was diluted with
CH.sub.2Cl.sub.2 and H.sub.2O and the organic phase was separated.
The aqueous phase was re-extracted (CH.sub.2Cl.sub.2) and the
combined organics were washed (saturated aqueous NaCl), dried
(MgSO.sub.4), filtered and concentrated to give a solid residue.
The residue was purified by flash chromatography
(EtOAc/CH.sub.2Cl.sub.2 0:100 then 50:50 then 80:20) to give
1,1'-bis(4-bromobenzyl)-1H,1'H-2,2'-biimidazole (4.12 g, 56%) as a
colourless solid. .sup.1H NMR (CDCl.sub.3, 400 MHz) .delta. 5.66
(s, 4H), 6.86-6.91 (m, 4H), 6.93 (d, J 1.2 Hz, 2H), 7.11 (d, J 1.2
Hz, 2H), 7.33-7.39 (m, 4H); .sup.13C NMR (CDCl.sub.3, 100 MHz)
.delta. 50.2, 121.5, 121.7, 128.5, 129.1, 131.8, 136.3, 138.0; HRMS
(EI) m/z 469.9741 C.sub.20H.sub.16N.sub.4Br.sub.2 [M].sup.+.cndot.
requires 671.2918.
Synthetic Example 12
1,1'-bis(4-(9H-carbazol-9-yl)benzyl)-1H,1'H-2,2'-biimidazole
##STR00023##
[0104] A mixture of 1,1'-bis(4-bromobenzyl)-1H,1'H-2,2'-biimidazole
(1.95 g, 4.13 mmol), 9H-carbazole (2.76 g, 16.5 mmol),
1,2-diaminocyclohexane (mixture of cis/trans, 220 .mu.L, 1.8 mmol)
and K.sub.3PO.sub.4 (2.63 g, 12.4 mmol) in toluene (120 mL) was
degassed (N.sub.2 bubbling, 15 min). CuI (240 mg, 1.2 mmol) was
added and the mixture was heated under reflux (72 h). The mixture
was allowed to cool to room temperature and filtered through Celite
washing with CH.sub.2Cl.sub.2. The combined filtrate and washings
were concentrated. The mixture was diluted with CH.sub.2Cl.sub.2
and H.sub.2O and the organic phase was separated. The aqueous phase
was re-extracted (CH.sub.2Cl.sub.2) and the combined organics were
washed (saturated aqueous NaCl), dried (MgSO.sub.4), filtered and
concentrated to give a solid residue. The residue was purified by
flash chromatography (EtOAc/CH.sub.2Cl.sub.2/MeOH 39:60:1 then
38:60:2) to give 1,1'-bis(4-(9H-(1.05 g, 39%) as a colourless
solid. .sup.1H NMR (CDCl.sub.3, 400 MHz) .delta. 5.96 (s, 4H), 7.10
(d, J 1.2 Hz, 2H), 7.22-7.28 (m, 6H), 7.30-7.38 (m, 8H), 7.42-7.47
(m, 4H), 7.48-7.53 (m, 4H), 8.11 (dt, J 7.6, 0.9 Hz, 4H); .sup.13C
NMR (CDCl.sub.3, 100 MHz) .delta. 50.6, 109.6, 120.0, 120.3, 121.6,
123.4, 125.9, 127.2, 128.7, 129.1, 136.6, 137.3, 138.4, 140.6.
Device Fabrication
[0105] OLEDs were fabricated in a Kitano Seiki KVD OLED Evo II
system (base pressure of 10.sup.-6 Pa) on commercially patterned
indium tin oxide (ITO) coated glass (NA-32R Alumino Silicate, 25
mm.times.25 mm) having a sheet
resistance.ltoreq.12.OMEGA./.quadrature. (Sanyo Vacuum) using
stainless steel shadow masks to define the device area (10
mm.sup.2).
[0106] Substrates were ultrasonically cleaned with a standard
regimen of de-ionised water (Millipore Direct-Q 3) with 5%
concentration of deconex FPD-211 (Borer Chemie), de-ionised water,
isopropyl alcohol (Aldrich), de-ionised water and isopropyl alcohol
followed by drying with nitrogen gas (Entegris Wafergard GN Gas
Filter Gun) and a UV-ozone treatment (Novascan) for 15 minutes.
[0107] Following the deposition of the organic layers, lithium
fluoride (LiF) and aluminium (Al), the devices were encapsulated
with a desiccant (Dynic) in a dry nitrogen atmosphere (MBraun
MB20/200, <1 ppm H.sub.2O/O.sub.2) using a recessed glass can
(IND26) and ultraviolet curable resin (Nagase Chemtex XNR5516Z-B1)
perimeter seal.
Device Example 1
[0108] The device structure for the OLED is shown in FIG. 5 and is
as follows:
Device A
[0109] Device A comprises 150 nm ITO (anode)/50 nm .alpha.-NPD
(hole-transport layer)/40 nm CBP doped with Flrpic [8% by weight]
(emissive layer)/40 nm BCP (hole blocking/electron transport
layer)/1 nm LiF (electron-injection layer)/100 nm Al (cathode),
where .alpha.-NPD is N,N'
bis(napthalen-1-yl)-N,N'-bis(phenyl)-2,2'-dimethylbenzidine, CBP is
4,4'-di(9H-carbazol-9-yl)biphenyl, Flrpic is
bis(4,6-difluorophenylpyridinato-N,C2)picolinatoiridium and BCP is
2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline. .alpha.-NPD, CBP,
Flrpic and BCP were purchased from Luminescence Technology Corp.
The thickness of each layer was measured by a quartz crystal
microbalance (ULVAC CR.TM.-9000) calibrated by a stylus profiler
(Bruker Dektak 150).
Device B
[0110] Device B was fabricated using the compound of synthetic
example 1
(1,1-bis(9-phenyl-9H-carbazol-3-yl)-1H,1'H-2,2'-biimidazole,
synthesized by the authors and purified by gradient sublimation
prior to use) in place of CBP in conditions directly analogous to
Device A.
Device Characterisation
[0111] Voltage-current-luminance (V-1-L) measurements were taken
using a Keithley 2400 SourceMeter and TOPCON BM-7A luminance
colormeter (0.2.degree. measurement angle). [0112] The Commission
International d'Eclairage (CIE) chromaticity coordinates (x,y) and
peak emission wavelength (.lamda.P) were calculated from the
electroluminescent (EL) spectral power distribution (SPD) measured
using a Sphere Optics LCS-100 Characterisation System. [0113]
Calculation of the external quantum efficiency (EQE) was determined
from the forward intensity assuming a Lambertian distribution of
the EL emission. [0114] The device performance is summarised in
Table 1.
TABLE-US-00001 [0114] TABLE 1 Device performance data for both host
materials CBP (Device A) and the compound of example 1 (Device B).
j V L CIE1931 L/j .eta. Host (mA/cm.sup.2) (V) (cd/m.sup.2) x y
(cd/A) (lm/W) CBP 1 8.7 101 0.17 0.32 10.1 3.6 Example 1 1 4.8 255
0.18 0.40 25.5 16.6 compound
[0115] At a current density of 1 mA/cm2, Device A (CBP) showed a
current efficiency of 10.1 cd/A and a brightness of 101 cd/m2. The
colour was blue and the CIE co-ordinates were (0.17, 0.32).
[0116] At a current density of 1 mA/cm2, Device B (1) showed a
current efficiency of 25.5 cd/A and a brightness of 255 cd/m2. The
colour was blue and the CIE co-ordinates were (0.18, 0.40).
Device Example 2
[0117] The device structure for the OLED is shown in FIG. 6 and is
as follows:
Device C
[0118] Device C comprises 145 nm ITO (anode)/70 nm TcTa
(hole-transport layer)/40 nm MCP doped with FlrPic [6% by weight]
(emissive layer)/40 nm TmPyPB (electron transport layer)/1 nm LiF
(electron-injection layer)/100 nm Al (cathode), where TcTa is
4,4',4''-tris(carbazol-9-yl)triphenylamine, MCP is
1,3-bis(carbazol-9-yl)benzene, FlrPic is
bis(4,6-difluorophenylpyridinato-N,C2)picolinatoiridium and TmPyPB
is 1,3,5-tri[(3-pyridyl)-phen-3-yl]benzene. TcTa, MCP, FlrPic and
TmPyPB were purchased from Luminescence Technology Corp. The
thickness of each layer was measured by a quartz crystal
microbalance (ULVAC CR.TM.-9000) calibrated by a stylus profiler
(Bruker Dektak 150).
Device D
[0119] Device D was fabricated using the compound of synthetic
example 1
(1,1-bis(9-phenyl-9H-carbazol-3-yl)-1H,1'H-2,2'-biimidazole,
(synthesized by the authors and purified by gradient sublimation
prior to use) in place of MCP in conditions directly analogous to
Device C.
[0120] Device Characterisation [0121] Device characterisation is as
for Device example 1. [0122] The device performance for Device
example 2 is summarised in Tables 2 and 3.
TABLE-US-00002 [0122] TABLE 2 Device performance data for both host
materials MCP (Device C) and the compound of example 1 (Device D)
at 1000 cd/m.sup.2. j L L/j .eta. (mA/ V (cd/ CIE1931 (cd/ (lm/
.lamda.P t1/2 Device cm2) (V) m2) x y A) W) (nm) (hours) C 2.7 6.1
1000 0.16 0.30 37.1 19.0 470 0.2 D 3.8 7.2 1000 0.16 0.32 26.2 11.5
472 4.6
[0123] At a brightness of 1000 cd/m.sup.2, Device C (MCP) showed a
current efficiency of 37.1 cd/A and a half life of 0.2 hours. The
colour was blue and the CIE co-ordinates were (0.16, 0.30).
[0124] At a brightness of 1000 cd/m.sup.2, Device D (1) showed a
current efficiency of 26.2 cd/A and a half life of 4.6 hours. The
colour was blue and the CIE co-ordinates were (0.16, 0.32).
TABLE-US-00003 TABLE 3 Device performance data for both host
materials MCP (Device C) and the compound of example 1 (Device D)
at 15,000 cd/m.sup.2. j V L CIE1931 L/j .eta. Device (mA/cm2) (V)
(cd/m2) x y (cd/A) (lm/W) C 124.5 11.0 15,000 0.16 0.31 12.0 3.4 D
84.8 10.9 15,000 0.16 0.31 17.7 4.9
[0125] At a brightness of 15000 cd/m.sup.2, Device C (MCP) showed a
current density of 124.5 mA/cm.sup.2 and a current efficiency of
12.0 cd/A. The colour was blue and the CIE co-ordinates were (0.16,
0.31).
[0126] At a brightness of 15000 cd/m.sup.2, Device D (1) showed a
current density of 84.8 mA/cm.sup.2 and a current efficiency of
17.7 cd/A. The colour was blue and the CIE co-ordinates were (0.16,
0.31).
* * * * *