Cerium and Europium Doped Phosphor Compositions and Light Emitting Devices Including the Same

• US 20090121615A1
• Filed: 10/14/2008
• Published: 05/14/2009
• Est. Priority Date: 11/14/2007
• Status: Active Grant

• Current Assignee: CREE Led Incorporated (Smart Global Holdings Incorporated)
• Original Assignee: CREE Incorporated (Wolfspeed, Inc.)
• Inventors: Le Toquin, Ronan P.
• Granted Patent: US 8,119,028 B2
• Time in Patent Office: Days
• US Class Current: 313/503
• CPC Class Codes: C09K 11/0883 Arsenides; Nitrides; Phosphides
• CPC Class Codes: C09K 11/77218 Silicon Aluminium Nitrides or Silicon Aluminium Oxynitrides
• CPC Class Codes: C09K 11/77348 Silicon Aluminium Nitrides or Silicon Aluminium Oxynitrides
• CPC Class Codes: C09K 11/77928 Silicon Aluminium Nitrides or Silicon Aluminium Oxynitrides
• CPC Class Codes: H01L 2224/32245 the item being metallic
• CPC Class Codes: H01L 2224/48091 Arched
• CPC Class Codes: H01L 2224/48247 connecting the wire to a bond pad of the item
• CPC Class Codes: H01L 2224/73265 Layer and wire connectors
• CPC Class Codes: H01L 2224/8592 Applying permanent coating, e.g. protective coating
• 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 2924/00012 Relevant to the scope of the group, the symbol of which is combined with the symbol of this group
• CPC Class Codes: H01L 2924/00014 the subject-matter covered by the group, the symbol of which is combined with the symbol of this group, being disclosed without further technical details
• CPC Class Codes: H01L 2924/181 Encapsulation
• CPC Class Codes: H01L 33/502 Wavelength conversion materials
• CPC Class Codes: Y02B 20/00 Energy efficient lighting technologies, e.g. halogen lamps or gas discharge lamps

Abstract

Compounds of Formula I, which include both cerium and europium, may be useful as phosphors in solid state light emitting devices. Light emitting devices including such phosphors may emit warm white light.

Claims

1. A phosphor comprising a compound of Formula I:

A_aB_bC_cD_dE_e 

 

(I)

wherein A comprises one or more elements selected from the group consisting of Ca, Sr, Ba, Mg, Y, Hf, the lanthanide elements and the alkaline metals;

B comprises Eu and Ce;

C comprises one or more tetrahedrally-coordinated trivalent elements;

D comprises one or more tetrahedrally-coordinated tetravalent elements;

E comprises one or more elements selected from the group consisting of N, O, F, C, S, Cl, Br and I, wherein a+b=1 and c+d=2;

and the compound has a CaAlSiN₃-type crystal structure.

2. The phosphor according to claim 1, wherein a, b, c, d and e satisfy the following requirements:

a is in a range of 0.7 to 1.3;

b is in a range of 0.01 to 0.3;

c is in a range of 0.5 to 1.5;

d is in a range of 0.5 to 1.5;

e is in a range of 2.5 to 3.5.

3. The phosphor according to claim 1, wherein b is in a range of 0.05 to 0.2.

4. The phosphor according to claim 1, wherein A comprises one or more of elements selected from the group consisting of Mg, Ba, Sr and Ca.

5. The phosphor according to claim 4, wherein A comprises Ca.

6. The phosphor according to claim 1, wherein C comprises one or more elements selected from the group consisting of Al, B, Ga, P, In, Sc, Y, Gd, Lu and Zr.

7. The phosphor according to claim 6, wherein C comprises Al.

8. The phosphor according to claim 1, wherein D comprises one or more elements selected from the group consisting of Si, Ge, Sn, Ti, Zr and Hf.

9. The phosphor according to claim 8, wherein D comprises Si.

10. The phosphor according to claim 1, wherein E comprises N, C, S, Cl, Br, I and/or F.

11. The phosphor according to claim 10, wherein E comprises N.

12. The phosphor according to claim 1, wherein A comprises Sr and Ca, wherein χ

(Sr)+χ

(Ca)=1.

13. The phosphor according to claim 1, wherein C comprises Al and D comprises Si, wherein c+d=2.

14. The phosphor according to claim 1, wherein E comprises O and N, and χ

(O)+χ

(N)=3.

15. The phosphor according to claim 1, wherein the compound of Formula I is present as a powder having an average particle size in a range of about 0.5 μ

m to about 30 μ

m.

16. The phosphor according to claim 1, wherein cerium and europium are together present in the compound at concentration in a range of about 0.1% to about 20% by weight.

17. The phosphor according to claim 1, which has a maximum emission wavelength in a range of 500 to 700 nm.

18. The phosphor according to claim 17, wherein the maximum emission wavelength occurs when the phosphor is irradiated with radiation in a range of about 380 nm to about 480 nm.

19. The phosphor according to claim 18, wherein the full width at half maximum is less than about 200=nm.

20. A light emitting device comprising

the phosphor according to claim 1;

and

a light emitting source.

21. The light emitting device of claim 20, wherein the phosphor is dispersed within a silicone encapsulant.

22. The light emitting device according to claim 20, wherein the light emitting source emits radiation with a maximum emission at a wavelength in a range of about 380 to about 470 nm, and wherein the phosphor absorbs at least some of the light emitted from the light emitting source and emits light having a maximum emission at a wavelength in a range of about 500 to about 700 nm.

23. The light emitting device according to claim 22, wherein the full width at half maximum of the light emitted from the phosphor is in a range of about 120 to about 200 nm.

24. The light emitting device according to claim 20, which has a color rendering index (CRI) of at least 80.

25. The light emitting device according to claim 20, having a correlated color temperature in a range of about 2500 to about 4500 K.

26. The light emitting device according to claim 20, having a conversion efficiency in a range of about 60 to about 100%.

27. The light emitting device according to claim 20, further comprising a scattering layer applied to the surface of the phosphor.

28. The light emitting device according to claim 27, wherein the scattering layer comprises ZnO, TiO₂, Al₂O₃, SrO₂ and/or ZrO₂.

29. The light emitting device according to claim 20, further comprising a inert or emissive layer applied to a surface of the phosphor.

30. A light emitting device, comprising:

a light emitting element configured to emit light at a wavelength in a range of about 380 nm to about 470 nm;

a phosphor configured to absorb at least some of the light emitted from the light emitting element, wherein the phosphor emits light having a maximum emission wavelength in a range of about 500 to about 700 nm;

wherein the full width at half maximum of the light emitted from the phosphor is in a range of about 120 to about 200 nm.

31. The light emitting device of claim 30, wherein the conversion efficiency of the phosphor is in a range of about 60 to about 100%.