Encapsulation for phosphor-converted white light emitting diode

• US 9,287,469 B2
• Filed: 05/02/2008
• Issued: 03/15/2016
• Est. Priority Date: 05/02/2008
• Status: Active Grant

• Current Assignee: Creeled Incorporated
• Original Assignee: CREE Incorporated (Wolfspeed, Inc.)
• Inventors: Chakraborty, Arpan
• Primary Examiner(s): Ingham, John C
• Application Number:
  US12/151,089
• Publication Number:
  US 20090272996A1
• Time in Patent Office: 2,874 Days
• Field of Search: 257/99, 257/100, 257/E23.119, 438/27
• US Class Current: 1/1
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/0002 Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00
• CPC Class Codes: H01L 2933/0091 Scattering means in or on the semiconductor body or semiconductor body package H01L33/22 takes precedence
• CPC Class Codes: H01L 33/501 characterised by the materials, e.g. binder
• CPC Class Codes: H01L 33/56 Materials, e.g. epoxy or silicone resin
• CPC Class Codes: H01L 33/60 Reflective elements

Abstract

An improved light emitting device, especially a phosphor-converted white light device, wherein the light extraction efficiency and the color temperature distribution uniformity are improved by the introduction of both nanoparticles and light scattering particles proximate to the light source. Nanoparticles having a high index of refraction are dispersed throughout a wavelength conversion layer to adjust the index of refraction of the layer for improved light extraction. Light scattering particles may be dispersed in the wavelength conversion layer and/or in a surrounding medium to improve the spatial correlated color temperature uniformity.

Claims

1. A light emitting diode (LED) device, comprising:

an LED chip on a mount surface;

a conversion layer on said LED chip, said conversion layer comprising a binder material and a plurality of phosphor particles throughout said binder material;

a plurality of nanoparticles throughout said binder material such that the effective refractive index of a combination of said binder material and said nanoparticles is between the refractive index of said phosphor particles and the refractive index of a surrounding medium; and

a light scattering layer on said conversion layer and in contact with said mount surface, said light scattering layer comprising a plurality of light scattering particles throughout said surrounding medium, the refractive index of said light scattering particles being greater or less than the refractive index of said surrounding medium, wherein light conversion only takes place in the conversion layer.

2. The LED device of claim 1, wherein said conversion layer comprises greater than 5% nanoparticles by volume.

3. The LED device of claim 1, wherein said conversion layer comprises greater than 10% nanoparticles by volume.

4. The LED device of claim 1, wherein said conversion layer comprises 20-40% nanoparticles by volume.

5. The LED device of claim 1, wherein said conversion layer comprises approximately 20% nanoparticles by volume.

6. The LED device of claim 1, said light scattering particles comprising particles comprising a diameter of approximately 0.1-2 mm.

7. The LED device of claim 1, wherein said conversion layer comprises approximately 0.01-5% light scattering particles by volume.

8. The LED device of claim 1, further comprising an encapsulant substantially enveloping said LED chip and said conversion layer, such that said encapsulant comprises said light scattering layer.

9. The LED device of claim 8, wherein additional light scattering particles are throughout said encapsulant.

10. The LED device of claim 8, wherein said light scattering particles are throughout said binder material and said encapsulant.

11. The LED device of claim 1, wherein said nanoparticles are throughout said binder material such that the effective refractive index of said combination of said binder material and said nanoparticles is approximately 1.7.

12. The LED device of claim 1, further comprising a spacer layer interposed between said LED chip and said conversion layer.

13. The LED device of claim 1, wherein said nanoparticles comprise titanium (IV) dioxide (TiO₂) particles.

14. The LED device of claim 1, wherein said nanoparticles comprise diamond particles.

15. The LED device of claim 1, wherein a primary emission surface of said LED chip is textured.

16. The LED device of claim 1, further comprising a reflective element on said LED chip opposite said conversion layer.

17. The LED device of claim 1, wherein said LED chip is nitride based.

18. The LED device of claim 1, wherein said nanoparticles have a higher refractive index than said binder material.

19. A light emitting diode (LED) device, comprising:

an LED chip on a mount surface, said LED chip comprising a textured primary emission surface;

a wavelength conversion layer comprising a flat primary emission surface on said LED chip, wherein light conversion only takes place within said wavelength conversion layer, said conversion layer comprising;

a binder material comprising a first refractive index;

a plurality of phosphor particles throughout said binder material;

a plurality of nanoparticles throughout said binder material such that the effective refractive index of a combination of said binder material and said nanoparticles is between the refractive index of said phosphor particles and the refractive index of a surrounding medium; and

an encapsulant over said wavelength conversion material and in contact with said mount surface, said encapsulant comprising a plurality of light scattering particles throughout said surrounding medium, the refractive index of said light scattering particles being greater or less than the refractive index of said surrounding medium.

20. The LED device of claim 19, wherein said conversion layer comprises approximately 0.01-5% light scattering particles by volume.

21. The LED device of claim 19, wherein said encapsulant substantially envelopes said LED chip.

22. The LED device of claim 21, wherein additional light scattering particles are throughout said encapsulant.

23. The LED device of claim 21, wherein said light scattering particles are throughout said binder material and said encapsulant.

24. The LED device of claim 19, wherein said nanoparticles are throughout said binder material such that the effective refractive index of said combination of said binder material and said nanoparticles is approximately 1.7.

25. The LED device of claim 19, wherein said conversion layer comprises greater than 5% nanoparticles by volume.

26. The LED device of claim 19, wherein said conversion layer comprises greater than 10% nanoparticles by volume.

27. The LED device of claim 19, wherein said conversion layer comprises 20-40% nanoparticles by volume.

28. The LED device of claim 19, wherein said conversion layer comprises approximately 20% nanoparticles by volume.

29. The LED device of claim 19, said nanoparticles comprising titanium dioxide (TiO₂) particles.

30. The LED device of claim 19, said nanoparticles comprising diamond particles.

31. The LED device of claim 19, said light scattering particles comprising fused silica particles.

32. The LED device of claim 19, wherein said light scattering particles have a diameter of approximately 0.1-2 mm.

33. The LED device of claim 32, said light scattering particles comprising titanium dioxide (TiO₂) particles.

34. The LED device of claim 32, said light scattering particles comprising diamond particles.

35. The LED device of claim 32, said light scattering particles comprising fused silica particles.

36. The LED device of claim 19, further comprising a reflective element on said LED chip opposite said conversion layer.

37. The LED device of claim 19, wherein said LED chip comprises aluminum gallium indium nitride (AlGaInN) semiconductor layers.

38. The LED device of claim 19, wherein said nanoparticles have a higher refractive index than said binder material.

39. The LED device of claim 19, further comprising a spacer layer interposed between said textured primary emission surface and said conversion layer.

40. A light emitting diode (LED) device, comprising:

an LED chip on a mount surface, said LED chip comprising a textured primary emission surface;

a wavelength conversion layer on said LED chip, wherein said light conversion only takes place within said wavelength conversion layer, said conversion layer comprising;

a binder material comprising a first refractive index;

a plurality of phosphor particles throughout said binder material, wherein said plurality of phosphor particles comprises a mixture of phosphor particles comprising a diameter of less than approximately 10 nanometers and phosphor particles comprising a diameter greater than approximately 10 micrometers; and

a spacer layer interposed between said textured primary emission surface and said conversion layer, wherein said spacer layer has an index of refraction less than said conversion layer and said LED chip, wherein said spacer layer is conformal to said LED chip and wherein said wavelength conversion material is conformal to said spacer layer; and

an encapsulant over said LED chip and in contact with said mount surface comprising a plurality of light scattering particles throughout said encapsulant, the refractive index of said light scattering particles being greater or less than the refractive index of said encapsulant.

41. The LED device of claim 40, wherein said conversion layer comprises approximately 0.01-5% light scattering particles by volume.

42. The LED device of claim 40, wherein said encapsulant substantially envelopes said LED chip.

43. The LED device of claim 42, wherein additional light scattering particles are throughout said encapsulant.

44. The LED device of claim 40, wherein said light scattering particles are throughout said binder material and said encapsulant.

45. The LED device of claim 40, said light scattering particles comprising titanium dioxide (TiO2) particles comprising a diameter of approximately 0.1-2 mm.

46. The LED device of claim 40, said light scattering particles comprising diamond particles comprising a diameter of approximately 0.1-2 mm.

47. The LED device of claim 40, said light scattering particles comprising fused silica particles comprising a diameter of approximately 0.1-2 mm.

48. The LED device of claim 40, further comprising a reflective element on said LED chip opposite said conversion layer.

49. The LED device of claim 40, wherein said LED chip comprises aluminum gallium indium nitride (AlGaInN) semiconductor layers.

50. A light emitting diode (LED) device, comprising:

an LED chip on a mount surface;

a conversion layer on said LED chip, said conversion layer comprising a binder material and a plurality of phosphor particles throughout said binder material, wherein light conversion only takes place within said conversion layer;

a plurality of nanoparticles throughout said binder material such that the effective refractive index of a combination of said binder material and said nanoparticles is increased; and

an encapsulant over said conversion layer and in contact with said mount surface, said encapsulant comprising a plurality of light scattering particles throughout said encapsulant, the refractive index of said light scattering particles being greater or less than the refractive index of said encapsulant;

wherein said effective refractive index is between the refractive index of said phosphor particles and the refractive index of said encapsulant.

51. The LED device of claim 50, wherein said nanoparticles have a diameter smaller than the wavelength of light emitted from said LED chip.

52. The LED device of claim 50, wherein said nanoparticles comprise particles comprising a diameter less than about 10 nm.

53. The LED device of claim 50, wherein said nanoparticles are configured to downconvert at least some light emitted from said LED chip.

54. The LED device of claim 50, wherein said nanoparticles exhibit excitation in the blue and/or UV emission spectrum.

55. The LED device of claim 50, wherein said LED chip is configured to emit blue light;

and

wherein said nanoparticles are configured to absorb at least some of said blue light and re-emit red light.

56. The LED device of claim 50, wherein said nanoparticles comprise a second plurality of phosphor particles.

57. The LED device of claim 50, wherein said binder material is thermally conductive.

58. The LED device of claim 50, wherein said conversion layer is on a thermally conductive reflective element.