Light emitting diode (LED) device that produces white light by performing phosphor conversion on all of the primary radiation emitted by the light emitting structure of the LED device

• US 6,501,102 B2
• Filed: 08/28/2001
• Issued: 12/31/2002
• Est. Priority Date: 09/27/1999
• Status: Expired due to Term

• Current Assignee: Lumileds Lighting US LLC (Apollo Global Management, Inc.)
• Original Assignee: Lumileds Lighting US LLC (Apollo Global Management, Inc.)
• Inventors: Craford, George M., Mueller-Mach, Regina B., Mueller, Gerd O.
• Primary Examiner(s): Chaudhuri, Olik
• Assistant Examiner(s): LOUIE, WAI SING
• Application Number:
  US09/941,452
• Publication Number:
  US 20020003233A1
• Time in Patent Office: 490 Days
• Field of Search: 257/14, 257/15, 257/18, 257/20, 257/22, 257/94, 257/95, 257/96, 257/98, 257/103, 313/463, 313/467, 313/468, 313/473, 313/501, 313/502, 313/505
• US Class Current: 257/84
• CPC Class Codes: H01L 33/504 Elements with two or more wavelength conversion materials

Abstract

Presented is an LED device that produces white light by performing phosphor conversion on substantially all of the primary light emitted by the light emitting structure of the LED device. The LED device comprises a light emitting structure and at least one phosphor-converting element located to receive and absorb substantially all of the primary light. The phosphor-converting element emits secondary light at second and third wavelengths that combine to produce white light. Some embodiments include an additional phosphor-converting element, which receives light from a phosphor-converting element and emits light at a fourth wavelength. In the embodiments including an additional phosphor-converting element, the second, third, and fourth wavelengths combine to produce white light. Each phosphor-converting element includes at least one host material doped with at least one dopant. The phosphor-converting element may be a phosphor thin film, a substrate for the light emitting structure, or a phosphor powder layer.

Claims

1. A light emitting device for generating white light, the light emitting device comprising:

a light emitting structure that emits primary light of a first wavelength when driven, said first wavelength being shorter than about 460 nm; and

a phosphor-converting element located to receive and absorb substantially all of said primary light emitted by said light emitting structure, said phosphor-converting element emitting secondary light at second and third wavelengths that combine to produce white light, said phosphor-converting element generating said secondary light and said third wavelength in response to excitation by at least one of said primary light and said secondary light at said second wavelength, said phosphor-converting element comprising at least one host material doped with at least one dopant, and said white light appearing substantially white to an average human eye; and

wherein said at least one host material comprises at least one of a Yttrium-Aluminum-Oxide compound, SrGa₂S₄, a Yttrium-Aluminum-Lanthanide-Oxide compound, a Yttrium-Aluminum-Lanthanide-Gallium-Oxide compound, SrS and a Nitridosilicate.

2. The light emitting device of claim 1, wherein said at least one dopant is selected from a group consisting of Cerium, Europium, Holmium, Ytterbium, and Praseodymium.

3. The light emitting device of claim 1, wherein concentration of each of said at least one dopant is between about 0.01 mol % and about 5 mol %.

4. The light emitting device of claim 1, wherein said at least one host material comprises one of a substrate for said light emitting structure, a phosphor thin film, a phosphor powder, and a phosphor-converting dye.

5. The light emitting device of claim 1, wherein said phosphor-converting element comprises a substrate for said light emitting structure and said substrate comprises a Yttritum-Aluminum-Oxide compound.

6. The light emitting device of claim 5, wherein said substrate has a thickness between about 0.2 mm and about 0.4 mm, said light emitting structure emitting a peak wavelength of about 410-460 nm and a dopant in said YAG substrate emits a peak of about 550-570 nm.

7. The light emitting device of claim 5, wherein said substrate comprises a (Y_0.75Gd_0.25)AG substrate having a thickness between about 0.2 mm and about 0.4 mm, said light emitting structure emitting a peak wavelength of about 410-460 nm and a dopant in said YAG substrate emits a peak of about 575 nm.

8. The light emitting device of claim 1, wherein said phosphor-converting element is a first phosphor-converting element, further comprising a second phosphor-converting element, said second phosphor-converting element comprising at least one additional host material doped with at least one additional dopant, said at least one additional dopant emitting light at a fourth wavelength, said light at said fourth wavelength being emitted in response to excitation by at least one of (a) said primary light, (b) said secondary light at said second wavelength and (c) said secondary light at the third wavelength.

9. The light emitting device of claim 8, wherein said at least one additional host material comprises at least one of a Yttrium-Aluminum-Oxide compound, SrGa₂S₄, a Yttrium-Aluminum-Lanthanide-Oxide compound, a Yttrium-Aluminum-Lanthanide-Gallium-Oxide compound, a Nitridosilicate, and SrS.

10. The light emitting device of claim 8, wherein said at least one additional dopant is selected from a group consisting of Cerium, Europium, Holmium, Ytterbium, and Praseodymium.

11. The light emitting device of claim 8, wherein concentration of each of said at least one additional dopant is between about 0.01 mol % and about 5 mol %.

12. The light emitting device of claim 8, wherein said second phosphor-converting element comprises one of a substrate for said light emitting structure, a phosphor thin film, a phosphor powder mixed in with an epoxy, and a phosphor-converting dye.

13. The light emitting device of claim 8, further comprising a light-transmissive substrate located between said light emitting structure and said phosphor-converting element.

14. The light emitting device of claim 8, wherein said first phosphor-converting element comprises a first host material doped with a first dopant and a second host material doped with a second dopant and said second phosphor-converting element comprises a third host material doped with a third dopant, wherein said second wavelength has a peak at about 480-510 nm, said third wavelength has a peak at about 525-580 nm, and said fourth wavelength has a peak at about 610-630 nm, each of said wavelengths having a halfwidth between about 20-150 nm.

15. The light emitting device of claim 8, wherein said first phosphor-converting element comprises a first host material doped with a first dopant and a second host material doped with a second dopant, wherein each of said first host material doped with said first dopant and said second host material doped with said second dopant comprises SrGa₂S₄ doped with Cerium (SrGa₂S₄:

Ce³⁺) and each of said at least one additional host material doped with at least one additional dopant comprises SrS doped with Europium (SrS;

Eu²⁺).

16. The light emitting device of claim 15, wherein said first and second phosphor-converting elements comprise multiple layers of phosphor thin films, each phosphor thin film having a thickness of about 5-25 μ

m.

17. The light emitting device of claim 15, wherein said primary light has a peak wavelength shorter than or about equal to 400 nm, said second wavelength has a peak at about 450-490 nm, said third wavelength has a peak at about 525-555 nm, and said fourth wavelength has a peak at about 610-630 nm, each of said wavelengths having a halfwidth between about 20 nm and about 150 nm.

18. The light emitting device of claim 1, wherein said at least one host material and at least one dopant comprises a first host material doped with a first dopant and a second host material doped with a second dopant, said first dopant emitting said secondary light at said second wavelength and said second dopant emitting said secondary light at said third wavelength.

19. The light emitting device of claim 18, wherein the light of the second wavelength is bluish having a wavelength between about 460 nm and about 510 nm and wherein the light of said third wavelength is yellowish having a wavelength between about 550 nm and about 580 nm, the light of said second and third wavelengths combining to form white light.

20. The light emitting device of claim 18, wherein each of said first and second host materials has a thickness of about 5-70 μ

m.

21. The light emitting device of claim 18, further comprising a light-transmissive substrate, said light-transmissive substrate being located between said light emitting structure and said phosphor-converting element.

22. The light emitting device of claim 21, further comprising a reflective electrode disposed on a surface of said light emitting structure, said reflective electrode reflecting a portion of said primary light toward said light-transmissive substrate.

23. The light emitting device of claim 18, wherein said first and second host materials comprise first and second phosphor thin films, respectively, said first phosphor thin film being disposed on a surface of a substrate and said second phosphor thin film being disposed on said first phosphor thin film.

24. The light emitting device of claim 1, wherein said phosphor-converting element comprises one host material doped with a first dopant and a second dopant wherein said first dopant emits said secondary light at said second wavelength and said second dopant emits said secondary light at said third wavelength.

25. The light emitting device of claim 24, wherein said one host material is a Yttrium-Aluminum-Oxide substrate and said first dopant and said second dopant are selected from a group consisting of Cerium, Europium, Holmium, Ytterbium, and Praseodymium.

26. The light emitting diode device of claim 1, wherein said first wavelength corresponds to a peak wavelength of a first spectral band, said second wavelength corresponds to a peak wavelength of a second spectral band, and said third wavelength corresponds to a peak wavelength of a third spectral band.

27. The light emitting device of claim 1, further comprising a substrate for said light emitting structure, said substrate being located so that said light emitting structure is between said substrate and said phosphor-converting element.