OLEDs having increased external electroluminescence quantum efficiencies
OLED devices are disclosed having increased external electroluminescence quantum efficiencies, i.e., increased “out-coupling” efficiencies. OLED devices that have increased out-coupling efficiencies and that are also protected from environmental elements such as moisture and oxygen are also disclosed. The OLED device of the present invention comprises a substrate; an active region positioned on the substrate, wherein the active region comprises an anode layer, a cathode layer and a light-emitting layer disposed between the anode layer and the cathode layer; and a polymeric layer disposed (a) over the active region, (b) under the active region or (c) both over and under the active region. The polymeric layer has microparticles incorporated therein, and the microparticles are effective to increase the out-coupling efficiency of the OLED. In one embodiment, the OLED device comprises a composite barrier layer and the microparticles are incorporated in a polymeric planarizing sublayer of the composite barrier layer. The composite barrier layer in this embodiment also protects the OLED from damage caused by environmental elements such as moisture and/or oxygen.
1. An OLED device comprising:
(a) a substrate;
(b) an active region positioned over said substrate, wherein said active region comprises an anode layer, a cathode layer and a light-emitting layer disposed between the anode layer and the cathode layer; and
(c) a composite barrier layer disposed over said active region or under said active region, said composite barrier layer comprising an alternating series of one or more polymeric planarizing sublayers and one or more high-density sublayers, at least one of said polymeric planarizing sublayers having microparticles incorporated therein, said microparticles being effective to increase the out-coupling efficiency of the OLED.
2. The OLED of claim 1 , wherein the substrate comprises an inorganic material or an organic material.
3. The OLED of claim 2 , wherein the substrate comprises a transparent material.
4. The OLED of claim 2 , wherein the substrate comprises glass, metal, or a silicon-based material.
5. The OLED of claim 2 , wherein the substrate comprises a polymeric material.
6. The OLED of claim 5 , wherein the substrate comprises a flexible polymeric material.
7. The OLED of claim 5 , wherein the substrate comprises one or more polymeric materials selected from the group consisting of polyesters, polyolefins, polycarbonates, polyethers, polyimides and polyfluorocarbons.
8. The OLED of claim 1 , wherein the polymeric sublayer having said microparticles incorporated therein is disposed on a top surface of said substrate.
9. The OLED of claim 8 , wherein the substrate comprises glass or a transparent flexible polymeric material.
10. The OLED of claim 1 , wherein said composite barrier layer is disposed on a top surface of said substrate.
11. The OLED of claim 10 , wherein said substrate comprises glass or a transparent flexible polymeric material.
12. The OLED of claim 1 , wherein said composite barrier layer comprises an alternating series of two or more polymeric planarizing sublayers and two or more high-density sublayers.
13. The OLED of claim 12 , wherein said composite barrier layer is disposed over said active region.
14. The OLED of claim 12 , wherein said microparticles are incorporated within at least two of said polymeric planarizing sublayers.
15. The OLED of claim 12 , wherein said composite barrier layer is disposed on said substrate, and said microparticles are incorporated within a polymeric planarizing sublayer closest to said substrate.
16. The OLED of claim 12 , wherein said composite barrier layer is disposed on said substrate, and said microparticles are incorporated within a polymeric planarizing sublayer closest to said active region.
17. The OLED of claim 1 , wherein said composite barrier layer is disposed over said active region.
18. The OLED of claim 1 , wherein the active region comprises a pixel and the size of said microparticles is smaller than the smallest lateral dimension of said pixel.
19. The OLED of claim 18 , wherein the largest dimension of said pixel is from about 10 μm to about 300 μm and the size of said microparticles is from about 0.4 μm to about 10 μm.
20. The OLED of claim 1 , wherein said microparticles comprise a transparent inorganic or polymeric material.
21. The OLED of claim 20 , wherein said microparticles comprise glass.
22. The OLED of claim 20 , wherein said microparticles comprise a metal, a metal oxide or a ceramic material.
23. The OLED of claim 22 , wherein said microparticles comprise TiO 2 .
24. The OLED of claim 1 , wherein said microparticles comprise a material having a refractive index of about 1.7 or greater.
25. The OLED of claim 1 , wherein the refractive index of said microparticles is different from the refractive index of said polymeric sublayer.
26. The OLED of claim 25 , wherein the difference between the refractive index of said microparticles and the refractive index of said polymeric sublayer is greater than about 0.3.
27. The OLED of claim 1 , wherein said polymeric planarizing sublayer comprises a material selected from the group consisting of fluorinated polymers, parylenes, cyclotenes and polyacrylates.
28. The OLED device of claim 1 , wherein said high-density material is selected from the group consisting of metals, metal oxides, metal nitrides, metal carbides and metal oxynitrides.
29. The OLED device of claim 1 , wherein said high-density material is selected from the group consisting of silicon, silicon oxides, silicon nitrides, silicon carbides, silicon oxynitrides, indium oxides, indium tin oxides, zinc indium tin oxides, tin oxides, aluminum oxides, aluminum nitrides, and titanium oxides.
30. The OLED device of claim 1 , wherein said OLED device comprises a first composite barrier layer disposed over said active region and a second composite barrier layer disposed under said active region.