Title: Display devices with organic-metal mixed layer
Abstract: A display device composed of: (a) a cathode; (b) an anode; (c) a luminescent region between the cathode and the anode; and an optional region adjacent one of the electrodes, wherein at least one of the cathode, the anode, the luminescent region, and the optional region includes a metal-organic mixed layer composed of: (i) an inorganic metal containing material, (ii) an organic material, and (iii) optionally, at least one component selected from the group consisting of metals, organic materials, and inorganic materials.
Patent Number: 6,841,932 Issued on 01/11/2005 to Aziz, et al.
| Inventors:
|
Aziz; Hany (Burlington, CA);
Liew; Yoon-Fei (Singapore, SG);
Popovic; Zoran D. (Mississauga, CA);
Hu; Nan-Xing (Oakville, CA);
Paine; Anthony J. (Mississauga, CA)
|
| Assignee:
|
Xerox Corporation (Stamford, CT)
|
| Appl. No.:
|
117812 |
| Filed:
|
April 5, 2002 |
| Current U.S. Class: |
313/503; 313/502; 313/504; 428/690; 428/917 |
| Intern'l Class: |
H01J 001/62 |
| Field of Search: |
313/502,503,504,498,499,505,506,511,311
428/690,917,212
315/169.3
359/58,60
|
References Cited [Referenced By]
U.S. Patent Documents
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|
| 4287449 | Sep., 1981 | Takeda et al. | 313/509.
|
| 4356429 | Oct., 1982 | Tang | 313/503.
|
| 4539507 | Sep., 1985 | VanSlyke et al. | 313/504.
|
| 4652794 | Mar., 1987 | Waite et al. | 313/506.
|
| 4720432 | Jan., 1988 | VanSlyke et al. | 428/457.
|
| 4767966 | Aug., 1988 | Simopoulos et al. | 313/509.
|
| 4769292 | Sep., 1988 | Tang et al. | 428/690.
|
| 4885211 | Dec., 1989 | Tang et al. | 428/457.
|
| 5049780 | Sep., 1991 | Dobrowolski et al. | 313/509.
|
| 5141671 | Aug., 1992 | Bryan et al. | 252/301.
|
| 5150006 | Sep., 1992 | Van Slyke et al. | 313/504.
|
| 5151629 | Sep., 1992 | VanSlyke | 313/504.
|
| 5227252 | Jul., 1993 | Murayama et al. | 428/690.
|
| 5247190 | Sep., 1993 | Friend et al. | 257/40.
|
| 5276381 | Jan., 1994 | Wakimoto et al. | 313/504.
|
| 5516577 | May., 1996 | Matsuura et al. | 428/212.
|
| 5593788 | Jan., 1997 | Shi et al. | 428/690.
|
| 5601903 | Feb., 1997 | Fujii et al. | 428/212.
|
| 5728801 | Mar., 1998 | Wu et al. | 528/422.
|
| 5846666 | Dec., 1998 | Hu et al. | 428/690.
|
| 5935720 | Aug., 1999 | Chen et al. | 428/690.
|
| 5942340 | Aug., 1999 | Hu et al. | 428/690.
|
| 5952115 | Sep., 1999 | Hu et al. | 428/690.
|
| 6023073 | Feb., 2000 | Strite | 257/40.
|
| 6054809 | Apr., 2000 | Haynes et al. | 313/505.
|
| 6057048 | May., 2000 | Hu et al. | 428/690.
|
| 6130001 | Oct., 2000 | Shi et al. | 428/690.
|
| 6274979 | Aug., 2001 | Celii et al. | 313/506.
|
| 2001/0053462 | Dec., 2001 | Mishima | 313/504.
|
| 2003/0038593 | Feb., 2003 | Aziz et al. | 313/506.
|
| Foreign Patent Documents |
| 0 977 287 | Feb., 2000 | EP.
| |
| 0 977 288 | Feb., 2000 | EP.
| |
| 1 160 890 | Dec., 2001 | EP.
| |
| 6-187913 | Jul., 1994 | JP.
| |
| 8-222374 | Aug., 1996 | JP.
| |
| WO 01/06816 | Jan., 2001 | WO.
| |
| WO 01/08240 | Feb., 2001 | WO.
| |
Other References
Liew et al., U.S. Applictaion Ser. No. 09/800,716, Filed Mar. 8, 2001,
"Cathodes for Electroluminescent Devices Having Improved Contrast and
Reduced Dark Spot Growth" (D/A1034).
Burrows et al., "Realiabilty and Degradation of Organic Light Emitting
Devices," Appl. Phys. Lett. vol. 65, p. 2922-2924 (1994).
Liang-Sun Hung et al., "Reduction of Ambient Light Reflection in Organic
Light-Emitting Diodes," Advanced Materials vol. 13, pp. 1787-1790 (2001).
Liang-Sun Hung et al., U.S. Application Ser. No. 09/577,092 (filed May 24,
2000).
O. Renault et al., "A low reflectivity multilayer cathode for organic
light-emitting diodes," Thin Solid Films, vol. 379, pp. 195-198 (2000).
David Johnson et al., Technical Paper 33.3, "Contrast Enhancement of OLED
Displays," http://www.luxell.com/pdfs/OLED_tech_ppr.pdf, pp. 1-3 (Apr.
2001).
Junji Kido et al., "Bright organic electroluminescent devices having a
metal-doped electron-injecting layer," Applied Physics Letters vol. 73,
pp.2866-2868 (1998).
Jae-Gyoung Lee et al., "Mixing effect of chelate complex and metal in
organic light-emitting diodes," Applied Physics Letters vol. 72, pp.
1757-1759 (1998).
Jingsong Huang et al., "Low-voltage organic electroluminescent devices
using pin structures," Applied Physics Letters vol. 80, pp. 139-141
(2002).
L.S. Hung et al., "Sputter deposition of cathodes in organic light emitting
diodes," Applied Physics Letters, vol. 86, pp. 4607-4612 (1999).
Hany Aziz et al., U.S. Application Ser. No. 09/935,031, filed Aug. 22,
2001.
Bernius et al., "Development progress of electroluminescent polymeric
materials and devices," SPIE Conference on Organic Light Emitting
Materials and Devices III, Denver, Colorado, Jul. 1999, SPIE, vol. 3797,
pp. 129-137.
Baldo et al., "Highly efficient organic phosphorescent emmision from
organic electroluminescent devices," Nature vol. 395, pp. 151-154 (1998).
Kido et al., "White light emitting organic electroluminescent device using
lanthanide complexes," Jpn. J. Appl. Phys. vol. 35, pp. L394-L396 (1996).
|
Primary Examiner: Patel; Nimeshkumar D.
Assistant Examiner: Leurig; Sharlene
Attorney, Agent or Firm: Soong; Zosan S.
Parent Case Text
CROSS REFERENCE TO RELATED APPLICATIONS
This application is a continuation-in-part application of parent U.S.
application Ser. No. 09/800,716 (filed Mar. 8, 2001) now abandoned, from
which priority is claimed, the disclosure of which is totally incorporated
herein by reference.
Claims
We claim:
1. A display device comprising:
(a) a cathode;
(b) an anode; and
(c) a luminescent region between the cathode and the anode;
wherein at least one of the cathode, the anode, and the luminescent region
comprises a light absorbing binary metal-organic mixed layer consisting
of:
(i) a single inorganic metal containing material, wherein the metal of the
inorganic metal containing material is selected from the group consisting
of Cu, Ag, Au, Ni, Pd, Pt, Se, and Te, and
(ii) a single organic material
wherein the light absorbing metal-organic mixed layer is selected such that
the device reduces light reflection by at least about 30%.
2. The device of claim 1, wherein the metal of the inorganic metal
containing material is selected from the group consisting of Cu, Ag, and
Au.
3. The device of claim 1, wherein the metal of the inorganic metal
containing material is selected from the group consisting of Ni, Pd, and
Pt.
4. The device of claim 1, wherein the metal of the inorganic metal
containing material is selected from the group consisting of Se and Te.
5. The device of claim 1, wherein the cathode includes the metal-organic
mixed layer.
6. The device of claim 1, wherein the cathode includes the metal-organic
mixed layer and an electron injection region.
7. The device of claim 1, wherein the cathode includes a capping region.
8. The device of claim 1, wherein the luminescent region includes an
organic electroluminescent material.
9. The device of claim 1, wherein the luminescent region includes an
inorganic electroluminescent material.
10. The device of claim 1, wherein the node includes the metal-organic
mixed layer.
11. The device of claim 1, wherein the anode includes the metal-organic
mixed layer and a hole injection region.
12. The device of claim 1, wherein the anode includes a capping region.
13. The device of claim 1, wherein the metal of the inorganic metal
containing material is Ag and the organic material is
tris(8-hydoxyquinoline)aluminum.
14. The device of claim 1, wherein the device reduces light reflection by
at least about 50%.
15. The device of claim 1, wherein the cathode is a single layer consisting
of the metal-organic mixed layer.
16. The device of claim 1, wherein the anode is a single layer consisting
of the metal-organic mixed layer.
17. A display device comprising:
(a) a cathode;
(b) an anode;
(c) a luminescent region between the cathode and the anode; and
(d) a region adjacent an electrode selected from the group consisting of
the cathode and the anode, wherein the region includes a light absorbing
metal-organic mixed layer including:
(i) an inorganic metal containing material,
(ii) an organic material, and
(iii) optionally at least one component selected from the group consisting
of metals, organic materials, and inorganic materials
wherein the light absorbing metal-organic mixed layer is selected such that
the device reduces light reflection by at least about 30%.
18. The device of claim 17, wherein the metal of the inorganic metal
containing material is selected from the group consisting of Li, Na, K,
Rb, Cs, Be, Mg, Ca, Sr, Ba, Sc, Y, La, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W,
Mn, Tc, Fe, Ru, Os, Co, Rh, Ir, Ni, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga,
In, Sn, Pb, Sb, Bi, Se, Te, Ce, Nd, Sm, and Eu.
19. The device of claim 17, wherein the electrode includes a capping
region.
20. The device of claim 17, wherein the region is a single layer consisting
of the metal-organic mixed layer.
21. The device of claim 17, wherein the region comprises a plurality of
layers.
22. The device of claim 17, wherein the electrode is the cathode.
23. The device of claim 17, wherein the electrode is the anode.
24. The device of claim 17, wherein the metal-organic mixed layer includes
tris(8-hydroxyquinoline)aluminum and the metal in the inorganic metal
containing material is Ag.
25. The device of claim 17, wherein the device reduces light reflection by
at least about 50%.
26. A display device comprising:
(a) a cathode;
(b) an anode; and
(c) a luminescent region between the cathode and the anode;
wherein at least one of the cathode, the anode, and the luminescent region
comprises a light absorbing metal-organic mixed layer including:
(i) an inorganic metal containing material,
(ii) an organic material, and
(iii) at least one component selected from the group consisting of metals,
organic materials, and inorganic materials
wherein the light absorbing metal-organic mixed layer is selected such that
the device reduces light reflection by at least about 30%.
27. The device of claim 26, wherein the metal of the inorganic metal
containing material and the metals are selected from the group consisting
of Li, Na, K, Rb, Cs, Be, Mg, Ca, Sr, Ba, Sc, Y, La, Ti, Zr, Hf, V, Nb,
Ta, Cr, Mo, W, Mn, Tc, Fe, Ru, Os, Co, Rh, Ir, Ni, Pd, Pt, Cu, Ag, Au, Zn,
Cd, B, Al, Ga, In, Sn, Pb, Sb, Bi, Se, Te, Ce, Nd, Sm, and Eu.
28. The device of claim 26, wherein the cathode includes the metal-organic
mixed layer.
29. The device of claim 26, wherein the cathode includes the metal-organic
mixed layer and an electron injection region.
30. The device of claim 26, wherein the cathode includes a capping region.
31. The device of claim 26, wherein the luminescent region includes an
organic electroluminescent material.
32. The device of claim 26, wherein the luminescent region includes an
inorganic electroluminescent material.
33. The device of claim 26, wherein the node includes the metal-organic
mixed layer.
34. The device of claim 26, wherein the anode includes the metal-organic
mixed layer and a hole injection region.
35. The device of claim 26, wherein the anode includes a capping region.
36. The device of claim 26, wherein the cathode includes the metal-organic
mixed layer and the metal-organic mixed layer includes
tris(8-hydroxyquinoline)aluminum, Ag, and Ca.
37. The device of claim 26, wherein the cathode includes the metal-organic
mixed layer and the metal-organic mixed layer includes
tris(8-hydroxyquinoline)aluminum, Ag, Ca, and LiF.
38. The device of claim 26, wherein the cathode includes the metal-organic
mixed layer and the metal-organic mixed layer includes
tris(8-hydroxyquinoline)aluminum, Ag, Mg, and LiF.
39. The device of claim 26, wherein the device reduces light reflection by
at least about 50%.
40. The device of claim 26, wherein the cathode is single layer consisting
of the metal-organic mixed layer.
41. The device of claim 26, wherein the anode is a single layer consisting
of the metal-organic mixed layer.
42. An electroluminescent device comprising
(a) a cathode;
(b) an anode; and
(c) a luminescent region including an organic electroluminescent material
between the cathode and the anode;
wherein the cathode comprises a light absorbing metal-organic mixed layer
including:
(i) a metal,
(ii) an organic material, and
(iii) at least one component selected from the group consisting of metals,
organic materials, and inorganic materials
wherein the light absorbing metal-organic mixed layer is selected such that
the device reduces light reflection by at least about 30%.
43. The device of claim 42, wherein the cathode includes a plurality of
layers with the metal-organic mixed layer being in contact with the
luminescent region.
44. The device of claim 42, wherein the metal and the metals are selected
from the group consisting of Mg, Ag, Al, In, Ca, Sr, Au, Li, Cr.
45. The device of claim 42, wherein the inorganic materials are selected
from the group consisting of SiO, SiO.sub.2, LiF, and MF.sub.2.
46. The device of claim 42, wherein the organic materials include
tris(8-hydroxyquinolinate)aluminum.
47. The device of claim 42, wherein the metal-organic mixed layer includes
Mg, tris(8-hydroxyquinolinate)aluminum, and Ag.
48. The device of claim 42, wherein the device reduces light reflection by
at least about 50%.
49. The device of claim 42, wherein the cathode is a single layer
consisting of the metal-organic mixed layer.
Description
BACKGROUND OF THE INVENTION
Organic light emitting devices (OLEDs) represent a promising technology for
display applications. A typical organic light emitting device includes a
first electrode; a luminescent region comprising one or more
electroluminescent organic material(s); and a second electrode; wherein
one of the first electrode and the second electrode functions as a
hole-injecting anode, and the other electrode functions as an
electron-injecting cathode; and wherein one of the first electrode and the
second electrode is a front electrode, and the other electrode is a back
electrode. The front electrode is transparent (or at least partially
transparent) while the back electrode is usually highly reflective to
light. When a voltage is applied across the first and second electrodes,
light is emitted from the luminescent region and through the transparent
front electrode. When viewed under high ambient illumination, the
reflective back electrode reflects a substantial amount of the ambient
illumination to the observer, which results in higher ratios of reflected
illumination as compared to the device's own emission, resulting in
"washout" of the displayed image.
In order to improve the contrast of electroluminescent displays in general,
light absorbing layers as described, for example, in U.S. Pat. No.
4,287,449, or optical interference members as described, for example, in
U.S. Pat. No. 5,049,780, have been used to reduce the ambient illumination
reflection.
Another problem of known organic light emitting devices originates from the
use of metals with low work functions, and hence high reactivity, in the
cathodes. Due to their high reactivity, such cathode materials are
unstable in ambient conditions and react with atmospheric O.sub.2 and
water to form non-emissive dark spots. See, for example, Burrows et al.,
"Reliability and Degradation of Organic Light Emitting Devices," Appl.
Phys. Lett. Vol. 65, pp. 2922-2924 (1994). To reduce such ambient effects,
organic light emitting devices are typically hermetically sealed,
immediately after fabrication, under stringent conditions, such as, for
example, less than 10 ppm moisture atmospheres.
Thus, there is a need which the present invention addresses for new display
devices that avoid or minimize a number of the above mentioned problems.
In particular, as described herein, the present display devices provide in
embodiments a reduced light reflection.
Other documents that may be relevant to the present invention include the
following:
Liang-Sun Hung et al., "Reduction of Ambient Light Reflection in Organic
Light-Emitting Diodes," Advanced Materials Vol. 13, pp.1787-1790 (2001);
Liang-Sun Hung et al., U.S. application Ser. No. 09/577,092 (filed May 24,
2000);
EP 1 160 890 A2 (claims priority based on above U.S. application Ser. No.
09/577,092;
Japanese laid open patent document No. 8-222374 (laid open date Aug. 30,
1996);
O. Renault et al., "A low reflectivity multilayer cathode for organic
light-emitting diodes," Thin Solid Films, Vol. 379, pp.195-198 (2000);
WO 01/08240 A1;
WO 01/06816 A1;
David Johnson et al., Technical Paper 33.3, "Contrast Enhancement of OLED
Displays," http://www.luxell.com/pdfs/OLED_tech_ppr.pdf, pp. 1-3 (April
2001);
Junji Kido et al., "Bright organic electroluminescent devices having a
metal-doped electron-injecting layer," Applied Physics Letters Vol. 73,
pp.2866-2868 (1998);
Jae-Gyoung Lee et al., "Mixing effect of chelate complex and metal in
organic light-emitting diodes," Applied Physics Letters Vol. 72,
pp.1757-1759 (1998);
Jingsong Huang et al., "Low-voltage organic electroluminescent devices
using pin structures," Applied Physics Letters Vol. 80, pp.139-141 (2002);
L. S. Hung et al., "Sputter deposition of cathodes in organic light
emitting diodes," Applied Physics Letters, Vol. 86, pp. 4607-4612 (1999);
EP 0 977 287 A2;
EP 0 977 288 A2;
Hany Aziz et al., U.S. application Ser. No. 09/935,031, filed Aug. 22,
2001.
Other documents that may be relevant to the present application were
submitted in parent U.S. application Ser. No. 09/800,716 (filed Mar. 8,
2001), such other documents being:
U.S. Pat. No. 4,885,211;
U.S. Pat. No. 5,247,190;
U.S. Pat. No. 4,539,507;
U.S. Pat. No. 5,151,629;
U.S. Pat. No. 5,150,006;
U.S. Pat. No. 5,141,671;
U.S. Pat. No. 5,846,666;
U.S. Pat. No. 5,516,577;
U.S. Pat. No. 6,057,048
U.S. Pat. No. 5,227,252;
U.S. Pat. No. 5,276,381;
U.S. Pat. No. 5,593,788;
U.S. Pat. No. 3,172,862;
U.S. Pat. No. 4,356,429;
U.S. Pat. No. 5,601,903;
U.S. Pat. No. 5,935,720;
U.S. Pat. No. 5,728,801;
U.S. Pat. No. 5,942,340;
U.S. Pat. No. 5,952,115;
U.S. Pat. No. 4,720,432;
U.S. Pat. No. 4,769,292;
U.S. Pat. No. 6,130,001;
Bernius et al., "developmental progress of electroluminescent polymeric
materials and devices," SPIE Conference on Organic Light Emitting
Materials and Devices III, Denver, Colo., July 1999, SPIE, Vol. 3797, pp.
129-137;
Baldo et al., "highly efficient organic phosphorescent emission from
organic electroluminescent devices," Nature Vol. 395, pp. 151-154 (1998);
Kido et al., "white light emitting organic electroluminescent device using
lanthanide complexes," Jpn. J. Appl. Phys. Vol. 35, pp. L394-L396 (1996);
SUMMARY OF THE INVENTION
The present invention is accomplished in embodiments by providing display
device comprising:
(a) a cathode;
(b) an anode; and
(c) a luminescent region between the cathode and the anode;
wherein at least one of the cathode, the anode, and the luminescent region
comprises a binary metal-organic mixed layer consisting of:
(i) a single inorganic metal containing material, wherein the metal of the
inorganic metal containing material is selected from the group consisting
of Cu, Ag, Au, Ni, Pd, Pt, Se, and Te, and
(ii) a single organic material.
There is also provided in embodiments, a display device comprising:
(a) a cathode;
(b) an anode;
(c) a luminescent region between the cathode and the anode; and
(d) a region adjacent an electrode selected from the group consisting of
the cathode and the anode, wherein the region includes a metal-organic
mixed layer including:
(i) an inorganic metal containing material,
(ii) an organic material, and
(iii) optionally at least one component selected from the group consisting
of metals, organic materials, and inorganic materials.
In further embodiments of the present invention, there is provided a
display device comprising:
(a) a cathode;
(b) an anode; and
(c) a luminescent region between the cathode and the anode;
wherein at least one of the cathode, the anode, and the luminescent region
comprises a metal-organic mixed layer including:
(i) an inorganic metal containing material,
(ii) an organic material, and
(iii) at least one component selected from the group consisting of metals,
organic materials, and inorganic materials.
In still other embodiments, there is provided an electroluminescent device
comprising:
(a) a cathode;
(b) an anode; and
(c) a luminescent region between the cathode and the anode;
wherein the cathode comprises a metal-organic mixed layer including:
(i) a metal,
(ii) an organic material, and
(iii) at least one component selected from the group consisting of metals,
organic materials, and inorganic materials.
BRIEF DESCRIPTION OF THE DRAWINGS
Other aspects of the present invention will become apparent as the
following description proceeds and upon reference to the Figures which
represent illustrative embodiments:
FIG. 1 illustrates an organic light emitting device comprising a cathode
according to an embodiment of this invention;
FIG. 2 illustrates an organic light emitting device comprising a cathode
according to another embodiment of this invention;
FIG. 3 illustrates an organic light emitting device similar to the organic
light emitting device shown in FIG. 1 comprising a luminescent region
including a hole transport zone and an electron transport zone;
FIG. 4 illustrates an organic light emitting device comprising a
conventional cathode structure;
FIG. 5 illustrates an organic light emitting device comprising an
embodiment of a cathode according to this invention;
FIG. 6A shows a light emitting region of an organic light emitting device
including a conventional cathode immediately after device fabrication;
FIG. 6B shows the light emitting region of the organic light emitting
device of FIG. 6A after the device has been stored for 48 hours under
ambient conditions;
FIG. 7A shows a light emitting region of an organic light emitting device
including a cathode according to this invention immediately after device
fabrication;
FIG. 7B shows the light emitting region of the organic light emitting
device of FIG. 7A after the device has been stored for 48 hours under
ambient conditions;
FIG. 8 shows a graph of % reflection versus wavelength for a conventional
organic light emitting device and an organic light emitting device
according to this invention;
FIG. 9 shows a graph of % reflection versus wavelength for organic light
emitting device according to this invention at different viewing angles;
FIG. 10 shows a graph of % reflection versus wavelength for organic light
emitting device according to this invention having different metal-organic
mixed layer compositions;
FIG. 11 shows a graph of % reflection versus wavelength for a conventional
organic light emitting device and an organic light emitting device
according to this invention;
FIG. 12 illustrates an embodiment of the present display device where a
single layer electrode incorporates the MOML;
FIG. 13 illustrates an embodiment of the present display device where an
electrode includes the MOML and a capping region;
FIG. 14 illustrates an embodiment of the present display device where an
electrode includes a charge injection region and the MOML;
FIG. 15 illustrates an embodiment of the present display device where an
electrode includes a charge injection region, the MOML, and a capping
region;
FIG. 16 illustrates an embodiment of the present display device where the
luminescent region includes the MOML; and
FIG. 17 illustrates an embodiment of the present display device where the
MOML is located in a region that is not considered part of the adjacent
electrode.
Unless otherwise noted, the same reference numeral in different Figures
refers to the same or similar feature.
DETAILED DESCRIPTION
This invention in embodiments provides cathodes for electroluminescent
devices. This invention in embodiments also provides electroluminescent
devices comprising the cathodes. This invention in embodiments also
provides methods for forming the cathodes.
Cathodes according to embodiments of this invention can be used for example
in electroluminescent devices and, more specifically, in organic
electroluminescent devices (i.e., "organic light emitting devices" or
OLEDs). The cathodes can provide advantages including reduced light
reflection, and hence improved contrast. The cathodes can also provide
reduced growth rates of dark spots. Dark spots result from the exposure of
organic light emitting devices to ambient conditions.
An organic light emitting device 10 comprising an exemplary embodiment of a
cathode according to this invention is shown in FIG. 1. The organic light
emitting device 10 is formed over a substrate 20. The substrate 20 is
shown at the bottom for illustration only. Those having ordinary skill in
the art will understand that the organic light emitting device 10, as well
as other organic light emitting devices according to this invention
described below, can be used with substrates having any other suitable
location relative to the organic light emitting devices. The organic light
emitting device 10 comprises an anode 30; a luminescent region 40
comprising an organic luminescent material on the anode 30; and the
cathode 50 over the luminescent region 40.
The cathode 50 comprises a metal-organic mixed layer (MOML). The
metal-organic mixed layer comprises at least two components, especially at
least three components; namely, (i) at least one inorganic metal
containing material first component, (ii) at least one organic material
second component, and optionally (iii) at least one third component that
can be selected from metals, organic materials and/or inorganic materials.
In some embodiments, the cathode 50 can consist essentially of the
metal-organic mixed layer. In such embodiments, the metal-organic mixed
layer can comprise the components (i), (ii) and (iii), or it can consist
essentially of these components.
FIG. 2 shows an organic light emitting device 110 comprising a cathode 150
according to another embodiment of this invention. The cathode 150
comprises one or more optional layers in addition to the metal-organic
mixed layer. For example, the cathode can comprise one, two, three or more
such optional additional layers. The organic light emitting device 110 is
shown on a substrate 120. The organic light emitting device 110 comprises
an anode 130; a luminescent region 140 on the anode 130; and the cathode
150 over the luminescent region 140. In this exemplary embodiment, the
cathode 150 comprises a metal-organic mixed layer 160 and two additional
layers 170 and 180 formed over the metal-organic mixed layer 160.
The metal-organic mixed layer 160 comprises at least three components;
namely, (i) at least one inorganic metal containing material first
component, (ii) at least one organic material second component, and (iii)
at least one third component that can be selected from metals, organic
materials and/or inorganic materials.
In some embodiments, the metal-organic mixed layer can consist essentially
of the components (i), (ii) and (iii).
In embodiments of the cathodes comprising one or more such additional
layers, such as the cathode 150, the metal-organic mixed layer 160 acts as
an electron injection contact. The metal-organic mixed layer 160 is formed
to contact the luminescent region 140 of organic light emitting devices.
In embodiments of the cathodes according to this invention, the
metal-organic mixed layer can comprise metals having a work function less
than about 4 eV.
In such embodiments of the cathodes, the one or more additional layer(s) of
the cathodes can comprise at least one metal and/or at least one inorganic
material. Suitable exemplary metals that can be used in the additional
layer(s) include, but are not limited to, Mg, Ag, Al, In, Ca, Sr, Au, Li,
Cr and mixtures thereof. Suitable exemplary inorganic materials that can
be used in the additional layer(s) include, but are not limited to, SiO,
SiO.sub.2, LiF, MgF.sub.2 and mixtures thereof. For example, in the
cathode 150 shown in FIG. 2, the layer 170 can comprise Mg:Ag, Mg, Ag, Al,
In, Ca, Sr, Au, Li, Cr, SiO or SiO.sub.2, and the layer 180 can comprise
Ag, Al, In, SiO or SiO.sub.2.
The one or more additional layer(s) can have the same or different
functions from each other. For example, one or more additional layers of
the cathode can comprise, or can consist essentially of, a metal to form a
conductive layer with a low sheet resistance (e.g., <10.OMEGA./square).
In addition, one or more additional layers of the cathode can protect the
metal-organic mixed layer from the ambient by forming a passivating layer
(such as, for example, a moisture barrier) that prevents, or at least
reduces, the permeation of ambient moisture to the MOML, the luminescent
region and the anode. Also, one or more additional layers of the cathode
can act as a thermal protective layer to provide protection from device
shorting at elevated temperatures. For example, such protection can be
provided at temperatures ranging from about 60.degree. C. to about
110.degree. C., as discussed in more detail in U.S. application Ser. No.
09/770,154, filed Jan. 26, 2001, which is incorporated herein by reference
in its entirety.
Some embodiments of the cathodes according to this invention comprise a
metal-organic mixed layer, which comprises at least one additional metal
component. That is, the third component of the metal-organic mixed layer
is at least one metal. Exemplary preferred embodiments of such cathodes
comprise a metal-organic mixed layer including (1) Ag, (2)
tris(8-hydroxyquinolinate) aluminum (AlQ3) and (3) Mg. However, in such
embodiments, the third component can be any suitable one or more metal(s)
and is not limited to Mg.
In some embodiments of cathodes according to this invention, Ag is needed
to achieve desired contrast effects.
In cathodes and anodes according to this invention, both the thickness of
the metal-organic mixed layer and the mixing ratio of the components of
the metal-organic mixed layer are selected to achieve the desired cathode
and anode performance; namely, increased contrast and reduced dark spot
growth.
In embodiments, the thickness of the metal-organic mixed layer (MOML) can
be for example from about 50 nm to about 1,000 nm, and particularly, from
about 100 nm to about 600 nm.
Certain ranges of the mixing ratio of the different components of the
metal-organic mixed layer are most effective in achieving the reduced rate
of growth of dark spots in the luminescent region and/or the desired light
reflection reducing properties of the metal-organic mixed layer needed to
achieve improved contrast in organic light emitting devices. The preferred
ranges of the mixing ratio depend on the selected components that form the
metal-organic mixed layer.
For example, in metal-organic mixed layers formed of AlQ3+Mg+Ag, the mixing
ratio of the components of the metal-organic mixed layer can be from about
20 volume % to about 80 volume % of AlQ3, from about 80 volume % to about
20 volume % of Mg, and from about 1 volume % to about 20 volume % of Ag.
An illustrative range of the components is from about 30 volume % to about
50 volume % of AlQ3, from about 30 volume % to about 50 volume % of Mg,
and from about 2 volume % to about 10 volume % of Ag. An exemplary
preferred metal-organic mixed layer composition comprises about 47.4
volume % AlQ3, about 47.4 volume % Mg, and about 5.2 volume % Ag.
In other embodiments of the MOML according to this invention, AlQ3 can be
replaced by other suitable metal complexes of 8-hydroxy quinolines.
The thickness of metal-organic mixed layers according to this invention can
also be controlled to achieve the desired effects. For example, in
metal-organic mixed layers comprised of AlQ3+Mg+Ag, the illustrative
thickness range of the metal-organic mixed layer is from about 80 nm to
about 300 nm.
Exemplary metal-organic mixed layers according to this invention comprise
AlQ3+Mg+Ag, in a respective ratio of about 47.4 volume % of AlQ3: about
47.4 volume % of Mg: about 5.2 volume % of Ag. An illustrative thickness
of metal-organic mixed layers having this composition is about 150 nm.
The metal-organic mixed layer can be formed by any suitable process. For
example, the metal-organic mixed layer can be formed by thermal
deposition. As stated above, the metal-organic mixed layer comprises at
least two components, particularly at least three components. In
embodiments, the at least two components can be co-evaporated. The
deposition rate of each material component can be independently controlled
to achieve the desired mixing ratio of the components in the metal-organic
mixed layer.
In the organic light emitting devices 10, 110, the anode 30, 130,
respectively, can comprise suitable positive charge injecting electrodes
such as indium tin oxide (ITO), tin oxide, gold and platinum. Other
suitable materials for forming the anode include, but are not limited to,
electrically conductive carbon, .pi.-conjugated polymers such as
polyaniline, polythiophene, polypyrrole, and the like having, for example,
a work function equal to, or greater than, about 4 eV, and preferably from
about 4 eV to about 6 eV.
The anode 30, 130 can have any suitable form. A thin conductive layer can
be coated onto a light transmissive substrate, such as, for example, a
transparent or substantially transparent glass plate or plastic film.
Embodiments of organic light emitting devices can comprise a light
transmissive anode formed from tin oxide or indium tin oxide coated on
glass. Also, very thin light-transparent metallic anodes having a
thickness, for example, of less than about 200 .ANG., and, preferably,
from about 75 .ANG. to about 150 .ANG. can be used. These thin anodes can
comprise metals such as gold, palladium and the like. In addition,
transparent or semi-transparent thin layers of conductive carbon or
conjugated polymers such as polyaniline, polythiophene, polypyrrole and
the like can be used to form anodes. These thin layers can have a
thickness of, for example from 50 .ANG. to about 175 .ANG.. Additional
suitable forms of the anode 30, 130 are disclosed in U.S. Pat. No.
4,885,211, which is incorporated herein by reference in its entirety.
The thickness of the anode 30, 130 can range from about 1 nm to about 5000
nm. The preferred thickness range of the anode is dependent on the optical
constants of the anode material. One preferred thickness range of the
anode is from about 30 nm to about 300 nm. Although less preferred,
thicknesses outside of this range can also be used.
The luminescent region of the present display devices comprises in
embodiments at least one electroluminescent organic material. Suitable
organic electroluminescent materials include, for example,
polyphenylenevinylenes, such as poly(p-phenylenevinylene) PPV,
poly(2-methoxy-5-(2-ethylhexyloxy)1,4-phenylenevinylene) MEHPPV and
poly(2,5-dialkoxyphenylenevinylene) PDMeOPV, and other materials disclosed
in U.S Pat. No.5,247,190, which is incorporated herein by reference in its
entirety; polyphenylenes, such as poly(p-phenylene) PPP,
ladder-poly-para-phenylene (LPPP), and poly(tetrahydropyrene) PTHP; and
polyfluorenes, such as poly(9,9-di-n-octylfluorene-2,7-diyl),
poly(2,8-(6,7,12,12-tetraalkylindenofluorene) and copolymers containing
fluorenes such as fluorene-amine copolymers (see e.g., Bernius et al.,
"Developmental Progress of Electroluminescent Polymeric Materials and
Devices," Proceedings of SPIE Conference on Organic Light Emitting
Materials and Devices III, Denver, Colo., July 1999, Volume 3797, p. 129).
Another class of organic electroluminescent materials that can be utilized
in the luminescent region includes, but is not limited to, the metal
oxinoid compounds as disclosed in U.S. Pat. Nos. 4,539,507; 5,151,629;
5,150,006; 5,141,671 and 5,846,666, each incorporated herein by reference
in its entirety. Illustrative examples include
tris(8-hydroxyquinolinate)aluminum (AlQ3), which is one preferred example,
and bis(8-hydroxyquinolato)-(4-phenylphenolato)aluminum (BAlq) which is
another preferred example. Other examples of this class of materials
include tris(8-hydroxyquinolinate)gallium,
bis(8-hydroxyquinolinate)magnesium, bis(8-hydroxyquinolinate)zinc,
tris(5-methyl-8-hydroxyquinolinate)aluminum,
tris(7-propyl-8-quinolinolato)aluminum, bis[benzo{f}-8-quinolinate]zinc,
bis(10-hydroxybenzo[h]quinolinate)beryllium, and the like, and metal
thioxinoid compounds disclosed in U.S. Pat. No. 5,846,666 (which is
incorporated herein by reference in its entirety), such as metal
thioxinoid compounds of bis(8-quinolinethiolato)zinc,
bis(8-quinolinethiolato)cadmium, tris(8-quinolinethiolato)gallium,
tris(8-quinolinethiolato)indium, bis(5-methylquinolinethiolato)zinc,
tris(5-methylquinolinethiolato)gallium,
tris(5-methylquinolinethiolato)indium,
bis(5-methylquinolinethiolato)cadmium,
bis(3-methylquinolinethiolato)cadmium, bis(5-methylquinolinethiolato)zinc,
bis[benzo{f}-8-quinolinethiolato]zinc,
bis[3-methylbenzo{f}-8-quinolinethiolato]zinc,
bis[3,7-dimethylbenzo{f}-8-quinolinethiolato]zinc, and the like. Preferred
materials are bis(8-quinolinethiolato)zinc,
bis(8-quinolinethiolato)cadmium, tris(8-quinolinethiolato)gallium,
tris(8-quinolinethiolato)indium and bis[benzo{f}-8-quinolinethiolato]zinc.
More specifically, a class of organic electroluminescent materials that can
be used in the luminescent region comprises stilbene derivatives, such as
those disclosed in U.S. Pat. No. 5,516,577, incorporated herein by
reference in it entirety. A preferred stilbene derivative is
4,4'-bis(2,2-diphenylvinyl)biphenyl.
Another class of suitable organic electroluminescent materials suitable for
utilizing in the luminescent region is the oxadiazole metal chelates
disclosed in U.S. application Ser. No. 08/829,398, which is incorporated
herein by reference in its entirety. These materials include
bis[2-(2-hydroxyphenyl)-5-phenyl-1,3,4-oxadiazolato]zinc;
bis[2-(2-hydroxyphenyl)-5-phenyl-1,3,4-oxadiazolato]beryllium;
bis[2-(2-hydroxyphenyl)-5-(1-naphthyl)-1,3,4-oxadiazolato]zinc;
bis[2-(2-hydroxyphenyl)-5-(1-naphthyl)-1,3,4-oxadiazolato]beryllium;
bis[5-biphenyl-2-(2-hydroxyphenyl)-1,3,4-oxadiazolato]zinc;
bis[5-biphenyl-2-(2-hydroxyphenyl)-1,3,4-oxadiazolato]beryllium;
bis[2-hydroxyphenyl)-5-phenyl -1,3,4-oxadiazolato]lithium;
bis[2-(2-hydroxyphenyl)-5-p-tolyl-1,3,4-oxadiazolato]zinc;
bis[2-(2-hydroxyphenyl)-5-p-tolyl-1,3,4-oxadiazolato]beryllium;
bis[5-(p-tert-butylphenyl)-2-(2-hydroxyphenyl)-1,3,4-oxadiazolato]zinc;
bis[5-(p-tert-butylphenyl)-2-(2-hydroxyphenyl)-1,3,4-oxadiazolato]berylliu
m; bis[2-(2-hydroxyphenyl)-5-(3-fluorophenyl)-1,3,4-oxadiazolato]zinc;
bis[2-(2-hydroxyphenyl)-5-(4-fluorophenyl)-1,3,4-oxadiazolato]zinc;
bis[2-(2-hydroxyphenyl)-5-(4-fluorophenyl)-1,3,4-oxadiazolato]beryllium;
bis[5-(4-chlorophenyl)-2-(2-hydroxyphenyl)-1,3,4-oxadiazolato]zinc;
bis[2-(2-hydroxyphenyl)-5-(4-methoxyphenyl)-1,3,4-oxadiazolato]zinc;
bis[2-(2-hydroxy-4-methylphenyl)-5-phenyl-1,3,4-oxadiazolato]zinc;
bis[2-.alpha.-(2-hydroxynaphthyl)-5-phenyl-1,3,4-oxadiazolato]zinc;
bis[2-(2-hydroxyphenyl)-5-p-pyridyl-1,3,4-oxadiazolato]zinc;
bis[2-(2-hydroxyphenyl)-5-p-pyridyl-1,3,4-oxadiazolato]beryllium;
bis[2-(2-hydroxyphenyl)-5-(2-thiophenyl)-1,3,4-oxadiazolato]zinc;
bis[2-(2-hydroxyphenyl)-5-phenyl-1,3,4-thiadiazolato]zinc;
bis[2-(2-hydroxyphenyl)-5-phenyl-1,3,4-thiadiazolato]beryllium;
bis[2-(2-hydroxyphenyl)-5-(1-naphthyl)-1,3,4-thiadiazolato]zinc; and
bis[2-(2-hydroxyphenyl)-5-(1-naphthyl)-1,3,4-thiadiazolato]beryllium, and
the like; and the triazines including those disclosed in U.S. application
Ser. No. 09/489,144, filed on Jan. 21, 2000 and U.S. Pat. No. 6,057,048,
each incorporated herein in its entirety.
The luminescent region can further include from about 0.01 weight percent
to about 25 weight percent of a luminescent material as a dopant. Examples
of dopant materials that can be utilized in the luminescent region are
fluorescent materials, such as, for example, coumarin, dicyanomethylene
pyranes, polymethine, oxabenzanthrane, xanthene, pyrylium, carbostyl,
perylene, and the like. Another preferred class of fluorescent materials
are quinacridone dyes. Illustrative examples of quinacridone dyes include
quinacridone, 2-methylquinacridone, 2,9-dimethylquinacridone,
2-chloroquinacridone, 2-fluoroquinacridone, 1,2-benzoquinacridone,
N,N'-dimethylquinacridone, N,N'-dimethyl-2-methylquinacridone,
N,N'-dimethyl-2,9-dimethylquinacridone,
N,N'-dimethyl-2-chloroquinacridone, N,N'-dimethyl-2-fluoroquinacridone,
N,N'-dimethyl-1,2-benzoquinacridone, and the like as disclosed in U.S.
Pat. Nos. 5,227,252; 5,276,381 and 5,593,788, each incorporated herein in
its entirety. Another class of fluorescent materials that may be used is
fused ring fluorescent dyes. Exemplary suitable fused ring fluorescent
dyes include perylene, rubrene, anthracene, coronene, phenanthrecene,
pyrene and the like, as disclosed in U.S. Pat. No. 3,172,862, which is
incorporated herein by reference in its entirety. Also, fluorescent
materials include butadienes, such as 1,4-diphenylbutadiene and
tetraphenylbutadiene, and stilbenes, and the like, as disclosed in U.S.
Pat. Nos. 4,356,429 and 5,516,577, each incorporated herein by reference
in its entirety. Other examples of fluorescent materials that can be used
are those disclosed in U.S. Pat. No. 5,601,903, which is incorporated
herein by reference in its entirety.
Additionally, luminescent dopants that can be utilized in the light
luminescent region are the fluorescent dyes disclosed in U.S. Pat. No.
5,935,720 (which is incorporated herein by reference in its entirety),
such as, for example,
4-(dicyanomethylene)-2-I-propyl-6-(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H
-pyran (DCJTB); the lanthanide metal chelate complexes, such as for
example, tris(acety lacetonato)(phenanthroline)terbium, tris(acetyl
acetonato)(phenanthroline)europium, and tris(thenoyl
trisfluoroacetonato)(phenanthroline)europium, and those disclosed in Kido
et al., "White light emitting organic electroluminescent device using
lanthanide complexes," Jpn. J. Appl. Phys., Volume 35, pp. L394-L396
(1996), which is incorporated herein by reference in its entirety; and
phosphorescent materials, such as, for example, organometallic compounds
containing heavy metal atoms that lead to strong spin-orbit coupling, such
as those disclosed in Baldo et.al., "Highly efficient organic
phosphorescent emission from organic electroluminescent devices," Letters
to Nature, Volume 395, pp. 151-154 (1998), which is incorporated herein by
reference in its entirety. Preferred examples include
2,3,7,8,12,13,17,18-octaethyl-21H23H-phorpine platinum(II)(PtOEP) and fac
tris(2-phenylpyridine)iridium(Ir(ppy)3).
The luminescent region can also include one or more materials with
hole-transporting properties. Examples of hole-transporting materials that
can be utilized in the luminescent region include polypyrrole,
polyaniline, poly(phenylene vinylene), polythiophene, polyarylamine as
disclosed in U.S. Pat. No. 5,728,801, which is incorporated herein by
reference in its entirety, and their derivatives, and known semiconductive
organic materials; porphyrin derivatives such as
1,10,15,20-tetraphenyl-21H,23H-porphyrin copper (II) disclosed in U.S.
Pat. No. 4,356,429, incorporated herein by reference in its entirety;
copper phthalocyanine, copper tetramethyl phthalocyanine; zinc
phthalocyanine; titanium oxide phthalocyanine; magnesium phthalocyanine;
and the like.
A specific class of hole transporting materials that can be utilized in the
luminescent region are the aromatic tertiary amines such as those
disclosed in U.S. Pat. No. 4,539,507, which is incorporated herein by
reference in its entirety. Suitable exemplary aromatic tertiary amines
include, but are not limited to,
bis(4-dimethylamino-2-methylphenyl)phenylmethane, N,N,N-tri(p-tolyl)amine,
1,1-bis(4-di-p-tolylaminophenyl)cyclohexane,
1,1-bis(4-di-p-tolylaminophenyl)-4-phenyl cyclohexane,
N,N'-diphenyl-N,N'-bis(3-methylphenyl)-1,1'-biphenyl-4,4'-diamine,
N,N'-diphenyl-N,N'-bis(3-methylphenyl)-1,1'-biphenyl-4,4'-diamine,
N,N'-diphenyl-N,N'-bis(4-methoxyphenyl)-1,1'-biphenyl-4,4'-diamine,
N,N,N',N'-tetra-p-tolyl-1,1'-biphenyl-4,4'-diamine,
N,N'-di-1-naphthyl-N,N'-diphenyl-1,1'-biphenyl-4,4'-diamine,
N,N'-di(naphthalene-1-yl)-N,N'-diphenyl-benzidine ("NPB"), mixtures
thereof and the like. Another class of aromatic tertiary amines are
polynuclear aromatic amines. Examples of these polynuclear aromatic amines
include, but are not limited to,
N,N-bis-[4'-(N-phenyl-N-m-tolylamino)-4-biphenylyl]aniline;
N,N-bis-[4'-(N-phenyl-N-m-tolylamino)-4-biphenylyl]-m-toluidine;
N,N-bis-[4'-(N-phenyl-N-m-tolylamino)-4-biphenylyl]-p-toluidine;
N,N-bis-[4'-(N-phenyl-N-p-tolylamino)-4-biphenylyl]aniline;
N,N-bis-[4'-(N-phenyl-N-p-tolylamino)-4-biphenylyl]-m-toluidine;
N,N-bis-[4'-(N-phenyl-N-p-tolylamino)-4-biphenylyl]-p-toluidine;
N,N-bis-[4'-(N-phenyl-N-p-chlorophenylamino)-4-biphenylyl]-m-toluidine;
N,N-bis-[4'-(N-phenyl-N-m-chlorophenylamino)-4-biphenylyl]-m-toluidine;
N,N-bis-[4'-(N-phenyl-N-m-chlorophenylamino)-4-biphenylyl]-p-toluidine;
N,N-bis-[4'-(N-phenyl-N-m-tolylamino)-4-biphenylyl]-p-chloroaniline;
N,N-bis-[4'-(N-phenyl-N-p-tolylamino)-4-biphenylyl]-m-chloroaniline;
N,N-bis-[4'-(N-phenyl-N-m-tolylamino)-4-biphenylyl]-1-aminonaphthalene,
mixtures thereof and the like; 4,4'-bis(9-carbazolyl)-1,1'-biphenyl
compounds, such as, for example 4,4'-bis(9-carbazolyl)-1,1'-biphenyl and
4,4'-bis(3-methyl-9-carbazolyl)-1,1l'-biphenyl, and the like.
A specific class of the hole transporting materials that can be used in the
luminescent region are the indolo-carabazoles, such as those disclosed in
U.S. Pat. Nos. 5,942,340 and 5,952,115, each incorporated herein by
reference in its entirety, such as, for example,
5,11-di-naphthyl-5,11-dihydroindolo[3,2-b]carbazole, and
2,8-dimethyl-5,11-di-naphthyl-5,11-dihydroindolo[3,2-b]carbazole;
N,N,N'N'-tetraarylbenzidines, wherein aryl may be selected from phenyl,
m-tolyl, p-tolyl, m-methoxyphenyl, p-methoxyphenyl, 1-naphthyl, 2-naphthyl
and the like. Illustrative examples of N,N,N'N'-tetraarylbenzidine are
N,N;-di-1-naphthyl-N,N'-diphenyl-1,1'-biphenyl-4,4'-diamine, which is more
preferred;
N,N'-bis(3-methylphenyl)-N,N'-diphenyl-1,1'-biphenyl-4,4'-diamine;
N,N'-bis(3-methoxyphenyl)-N,N'-diphenyl-1,1'-biphenyl-4,4'-diamine, and
the like. Preferred hole transporting materials that can be used in the
luminescent region are the naphtyl-substituted benzidine derivatives.
The luminescent region can also include one or more materials with electron
transporting properties. An example of electron transporting materials
that can be utilized in the luminescent region is polyfluorenes, such as
poly(9,9-di-n-octylfluorene-2,7-diyl),
poly(2,8-(6,7,12,12-tetraalkylindenofluorene) and copolymers containing
fluorenes such as fluorene-amine copolymers, as disclosed in incorporated
Bernius et al., Proceedings of SPIE Conference on Organic Light Emitting
Materials and Devices III, Denver, Colo., July 1999, Volume 3797, p. 129.
Other examples of electron transporting materials that can be utilized in
the luminescent region can be selected from the metal oxinoid compounds,
the oxadiazole metal chelate compounds, the triazine compounds and the
stilbene compounds, examples of which have been described above in deta
