ORGANIC ELECTROLUMINESCENT DEVICE WITH A CERAMIC OUTPUT COUPLER AND METHOD OF MAKING THE SAME

• US 20040027062A1
• Filed: 01/16/2001
• Published: 02/12/2004
• Est. Priority Date: 01/16/2001
• Status: Active Grant

• Current Assignee: BOE Technology Group Co., Ltd.
• Original Assignee: General Electric Company
• Inventors: Shiang, Joseph John, Duggal, Anil Raj
• Granted Patent: US 6,703,780 B2
• Time in Patent Office: Days
• US Class Current: 313/506
• CPC Class Codes: H10K 50/85 Arrangements for extracting light from the devices
• CPC Class Codes: H10K 50/854 comprising scattering means
• CPC Class Codes: H10K 50/856 comprising reflective means
• CPC Class Codes: H10K 50/858 comprising refractive means, e.g. lenses

Abstract

An organic light emitting diode containing a first electrode, a second electrode, at least one organic light emitting layer, and a ceramic output coupler is provided. The index of refraction of the output coupler is matched to that of the adjacent layer of the device. The ceramic output coupler may be a ceramic substrate with a dimpled light emitting surface which reduces Fresnel and critical angle optical losses.

Claims

1. An organic electroluminescent light emitting device, comprising:

a first electrode;

a second electrode;

at least one organic light emitting layer; and

a ceramic output coupler.

2. The device of claim 1, wherein:

the device comprises an organic light emitting diode; and

the ceramic output coupler comprises a ceramic layer containing a light emitting surface of the device.

3. The device of claim 2, wherein:

the ceramic output coupler reduces a critical angle loss and a Fresnel loss; and

an index of refraction of the ceramic output coupler is matched to an index of refraction of an adjacent layer of the electroluminescent device.

4. The device of claim 3, wherein the index of refraction of the ceramic output coupler differs by 0.1 or less from the index of refraction of the adjacent layer of the electroluminescent device.

5. The device of claim 4, wherein the index of refraction of the ceramic output coupler is the same as the index of refraction of the adjacent layer of the electroluminescent device.

6. The device of claim 2, further comprising a transparent substrate between the ceramic output coupler and the at least one organic light emitting layer, wherein the index of refraction of the ceramic output coupler differs by 0.1 or less from an index of refraction of the substrate.

7. The device of claim 6, wherein the index of refraction of the ceramic output coupler is the same as or greater than the index of refraction of the substrate.

8. The device of claim 7, wherein the index of refraction of the ceramic output coupler is the same as the index of refraction of the substrate.

9. The device of claim 2, wherein the ceramic output coupler comprises a shaped ceramic material attached to the organic light emitting diode.

10. The device of claim 9, wherein the shaped ceramic material comprises translucent ceramic material having a corrugated or dimpled light emitting surface.

11. The device of claim 10, wherein each dimple has a height greater than 0.1 microns and a spacing between dimple or corrugation peaks is a factor of 10 or less of the dimple height.

12. The device of claim 11, wherein the dimples or corrugations have a sinusoidal, pseudo-pyramidal or conical shape.

13. The device of claim 2, wherein the ceramic output coupler randomly volume scatters light emitted by the organic light emitting layer to reduce a critical angle loss.

14. The device of claim 13, wherein the ceramic output coupler volume contains voids which randomly scatter light emitted by the organic light emitting layer.

15. The device of claim 2, wherein the ceramic output coupler material comprises Al₂O₃, Y₂O₃, Y₃Al₅O₁₂, MgAl₂O₄, MgAlON, AlN, AlON, or TiO₂ doped ZrO₂.

16. The device of claim 2, wherein the ceramic output coupler comprises a light emitting material.

17. The device of claim 16, wherein the light emitting material comprises a ceramic phosphor.

18. The device of claim 17, wherein the phosphor comprises YAG:

Ce³⁺.

19. The device of claim 2, wherein the ceramic output coupler comprises a ceramic matrix material containing light emitting particles.

20. The device of claim 19, wherein the light emitting particles comprise semiconductor particles.

21. The device of claim 2, wherein the ceramic output coupler comprises:

a first ceramic layer having a first index of refraction that is matched to an index of refraction of an adjacent layer of the electroluminescent device; and

a second ceramic layer having a second index of refraction lower than the first index of refraction.

22. The device of claim 21, wherein the first ceramic layer comprises Y₃Al₅O₁₂, and the second ceramic layer comprises MgAl₂O₄.

23. The device of claim 2, wherein the ceramic output coupler comprises a ceramic layer having a graded index of refraction, wherein an inner portion of the layer has a first index of refraction that is matched to an index of refraction of an adjacent layer of the electroluminescent device and an outer portion of the layer has a second index of refraction that is lower than the first index of refraction.

24. The device of claim 2, wherein:

the electroluminescent device emits white light;

the first electrode comprises a metal containing electrode;

the organic light emitting layer comprises at least one an organic molecule layer or at least one polymer layer over a first side of the first electrode;

the second electrode comprises a transparent electrode having a first side over the organic light emitting layer; and

further comprising a voltage source.

25. The device of claim 24, further comprising:

a first device electrical contact contacting a first side of the first electrode;

a second device electrical contact contacting a second side of the second electrode;

a sealing member over the second side of the second electrode;

a mounting substrate over the sealing member; and

a plurality of organic electroluminescent devices below the mounting substrate having a fill factor of greater than 0.3.

26. The device of claim 24, wherein:

a reflectivity of a non-light emitting side of the device is 80% or higher;

the output coupler optical thickness for scattering is about 0.1 to about 0.9; and

the device emission extraction is 53% or higher.

27. The device of claim 26, wherein:

a reflectivity of the first electrode is 86% or higher;

the output coupler optical thickness for scattering is about 0.5; and

the device emission extraction is 58% or higher.

28. The device of claim 2, wherein the ceramic output coupler comprises a first ceramic material having surface recesses at grain boundaries and a second ceramic material in the recesses between the first ceramic material and an adjacent layer of the device.

29. An organic electroluminescent light emitting device, comprising:

a first electrode;

at least one organic light emitting layer over the first electrode;

a second transparent electrode over the at least one organic light emitting layer; and

a shaped ceramic material over the second transparent electrode, wherein;

the shaped ceramic material contains a corrugated or dimpled light emitting surface and a voids through out is volume which scatter light emitted by the organic light emitting layer; and

an index of refraction of the shaped ceramic material is matched to an index of refraction of an adjacent layer of the electroluminescent device.

30. The device of claim 29, wherein the index of refraction of the ceramic shaped ceramic material differs by 0.1 or less from the index of refraction of the adjacent layer of the electroluminescent device or of a transparent substrate.

31. The device of claim 30, wherein the dimples have a sinusoidal, pseudo-pyramidal or conical shape.

32. The device of claim 31, wherein the ceramic shaped ceramic material comprises Al₂O₃, Y₂O₃, Y₃Al₅O₁₂, MgAl₂O₄, MgAlON, AlN, AlON, or TiO₂ doped ZrO₂.

33. The device of claim 32, wherein the shaped ceramic material comprises a ceramic phosphor or a ceramic matrix material containing light emitting particles.

34. The device of claim 30, wherein the ceramic shaped ceramic material comprises:

a first ceramic layer having a first index of refraction that is matched to an index of refraction of an adjacent layer of the electroluminescent device; and

a second ceramic layer having a second index of refraction lower than the first index of refraction.

35. The device of claim 30, wherein:

the electroluminescent device comprises an organic light emitting diode which emits white light;

the first electrode comprises a metal containing electrode;

the organic light emitting layer comprises at least one an organic molecule layer or at least one polymer layer over a first side of the first electrode;

the second electrode comprises a transparent electrode having a first side over the organic light emitting layer; and

further comprising a voltage source.

36. The device of claim 35, further comprising:

a first device electrical contact contacting the first side of the first electrode, wherein the first electrode comprises aluminum, silver or gold;

a second device electrical contact contacting a second side of the second electrode, wherein the second electrode comprises indium tin oxide;

a sealing member over the second side of the second electrode;

a mounting substrate over the sealing member; and

a plurality of organic electroluminescent devices below the mounting substrate having a fill factor of greater than 0.3.

37. A method of making an organic electroluminescent light emitting device, comprising:

forming a first electrode;

forming at least one organic light emitting layer;

forming a second electrode; and

forming a ceramic output coupler.

38. The method of claim 37, further comprising:

forming the first electrode of a transparent conductive material over a first surface of a glass or polymer substrate;

forming the at least one organic light emitting layer over the first electrode;

forming a second electrode of a metal material over the at least one organic light emitting layer; and

forming the ceramic output coupler over the second surface of the glass or polymer substrate.

39. The method of claim 37, further comprising:

forming the first electrode of a transparent conductive material over the ceramic output coupler which comprises a ceramic substrate;

forming the at least one organic light emitting layer over the first electrode; and

forming a second electrode of a metal material over the at least one organic light emitting layer.

40. The method of claim 37, wherein the step of forming the ceramic output coupler comprises:

placing a ceramic precursor material into a mold cavity;

solidifying the precursor material to form a shaped ceramic output coupler having a corrugated or dimpled first light emitting surface; and

attaching the output coupler to the organic electroluminescent light emitting device.

41. The method of claim 40, wherein the step of placing comprises injecting a viscous heated ceramic precursor into the mold cavity.

42. The method of claim 41, wherein the step of solidifying comprises cooling the precursor material in the mold cavity.

43. The method of claim 40, wherein the step of solidifying comprises die pressing a ceramic precursor powder into the output coupler in the mold cavity.

44. The method of claim 40, wherein the ceramic precursor material comprises a ceramic precursor powder and a binder.

45. The method of claim 44, further comprising sintering the solidified precursor material until the material has a porosity of 0.1% or less and a transmittance of 95% or more.

46. The method of claim 45, further comprising heating the precursor material to evaporate the binder.

47. The method of claim 45, further comprising selecting the sintering conditions, precursor powder composition and precursor powder size to form a ceramic output coupler whose the index of refraction differs by 0.1 or less from the index of refraction of the adjacent layer of the electroluminescent device and which contains voids which randomly scatter light emitted by the organic light emitting layer.

48. The device of claim 47, wherein the ceramic output coupler material comprises Al₂O₃, Y₂O₃, Y₃Al₅O₁₂, MgAl₂O₄, MgAlON, AlN, AlON, or TiO₂ doped ZrO₂.

49. The method of claim 37, wherein the ceramic output coupler comprises a

ceramic phosphor or a ceramic matrix material containing light emitting particles.

50. The method of claim 37, wherein the ceramic output coupler comprises:

a first ceramic layer having a first index of refraction that is matched to an index of refraction of an adjacent layer of the electroluminescent device; and

a second ceramic layer having a second index of refraction lower than the first index of refraction.

51. The method of claim 37, further comprising forming a second ceramic material in surface recesses at grain boundaries of the ceramic output coupler by a sol-gel method.

52. The method of claim 37, further comprising:

forming a glass plate over the first electrode;

forming a metal coating over the glass plate; and

attaching the organic electroluminescent light emitting device to a mounting substrate.

53. The method of claim 52, further comprising attaching a plurality of organic electroluminescent light emitting devices to the mounting substrate such that the devices have a fill factor of greater than 0.3.