Cerium based phosphor materials for solid-state lighting applications

• US 8,920,676 B2
• Filed: 10/02/2006
• Issued: 12/30/2014
• Est. Priority Date: 09/30/2005
• Status: Active Grant

• Current Assignee: Regents of the University of California (University of California)
• Original Assignee: Regents of the University of California (University of California)
• Inventors: Cheetham, Anthony K., Le Toquin, Ronan P.
• Primary Examiner(s): Hoban, Matthew E
• Application Number:
  US11/541,708
• Publication Number:
  US 20070159066A1
• Time in Patent Office: 3,011 Days
• Field of Search: 252/301.4 F, 313/503
• US Class Current: 252/301.4F
• CPC Class Codes: C09K 11/0883 Arsenides; Nitrides; Phosphides
• CPC Class Codes: C09K 11/77217 Silicon Nitrides or Silicon Oxynitrides
• CPC Class Codes: C09K 11/77218 Silicon Aluminium Nitrides or Silicon Aluminium Oxynitrides
• CPC Class Codes: H01L 33/502 Wavelength conversion materials
• CPC Class Codes: H05B 33/14 characterised by the chemical or physical composition or the arrangement of the electroluminescent material , or by the simultaneous addition of the electroluminescent material in or onto the light source
• CPC Class Codes: Y02B 20/00 Energy efficient lighting technologies, e.g. halogen lamps or gas discharge lamps

Abstract

A luminescent cerium (Ce) doped compound emitting bright red light, comprising a calcium silicate nitride ternary system, such as CaSiN_2-δO_δ:Ce³⁺, that crystallizes in a face-centered cubic unit cell with a lattice parameter of ˜a=14.88 Å. The Ce doped compound can be used for white light applications either: (i) to enhance the light quality of the system based on a blue LED with a yellow or green phosphor, (ii) as an orange phosphor in combination with a blue LED and a green phosphor, or (iii) as a red phosphor in a setup comprising a ultraviolet (UV) LED and red, green and blue (RGB) phosphors. Substitution of smaller elements on the Ca site or larger elements on the Si site leads to a decrease of the emission wavelength towards the yellow or orange region.

Claims

1. An apparatus for solid state lighting applications, comprising:

a light emitting diode (LED); and

a luminescent cerium (Ce) compound including Calcium (Ca), Silicon (Si), Nitrogen, Ce³⁺ doping, and a cubic unit cell, wherein the luminescent Ce compound emits orange to red light when the luminescent Ce compound is excited by radiation from the light emitting diode.

2. The apparatus of claim 1, wherein the light emitting diode is a blue light emitting diode and the luminescent Ce compound is adjacent the blue light emitting diode in combination with a yellow or green phosphor.

3. The apparatus of claim 1, wherein the light emitting diode is a blue light emitting diode and the luminescent Ce compound is adjacent the blue light emitting diode as an orange phosphor in combination with a green phosphor.

4. The apparatus of claim 1, wherein the light emitting diode is an ultraviolet (UV) light emitting diode and the luminescent Ce compound is adjacent the ultraviolet light emitting diode as a red phosphor in a group of red, green and blue (RGB) phosphors.

5. A composition of matter, comprising:

a luminescent cerium (Ce) compound including Calcium (Ca), Silicon (Si), Nitrogen, Ce³⁺ doping, and a cubic unit cell, wherein the luminescent Ce compound emits orange to red light when the luminescent Ce compound is excited by radiation having one or more wavelengths in a range from ultraviolet (UV) to green wavelengths.

6. The composition of matter of claim 5, wherein the luminescent Ce compound is excited by the radiation that is ultraviolet (UV) radiation.

7. The composition of matter of claim 5, wherein the luminescent Ce compound is described by the formula:

M_xB_yN_z-δ

O<sub>δ

;

Ce</sub>³⁺

wherein x≈

y≈

1, z=2, 0≧

δ

<

2 and M includes the calcium (Ca), B includes the Si, and N includes the Nitrogen.

8. The composition of matter of claim 5, further comprising at least one additional element on the site of the Ca.

9. The composition of matter of claim 5, further comprising Strontium (Sr) on a site of the Ca.

10. The composition of matter of claim 5, wherein the luminescent Ce compound'"'"'s formula comprises CaSiN_2-δ

O_δ

;

Ce³⁺ with 0≦

δ

<

2 .

11. The composition of matter of claim 5, further comprising one or more additional elements on a site of the Si.

16. The composition of claim 5, wherein the luminescent Ce compound has an excitation spectrum that peaks in a blue wavelength range.

17. The composition of matter of claim 5, wherein the light has a peak intensity in a red wavelength range.

18. The composition of matter of claim 5, wherein the light has a peak intensity in an orange wavelength range.

19. The composition of matter of claim 5, wherein an emission spectrum of the light has a full width at half maximum that includes one or more wavelengths corresponding to orange light.

20. The composition of matter of claim 5, wherein an emission spectrum of the light has a full width at half maximum that includes one or more wavelengths corresponding to red light.

21. The composition of matter of claim 5, wherein the Ce³⁺ is an emitter.

22. The composition of matter of claim 5, wherein the luminescent Ce compound has an excitation spectrum that peaks in a green wavelength range.

12. A method for creating a luminescent compound, comprising the steps of:

(a) mixing stoichiometric amounts of;

(1) Ca₃N₂ or Ca metal, (2) AlN, (3) Si₃N₄, Si₂N₂NH, or Si(NH)₂, and (4) a rare earth source either as a metal, a nitride, or an oxide, in order to form a mixture, wherein the rare earth source is cerium (Ce);

(b) weighing and grinding the mixture in conditions of [O₂] <

1 parts per million (ppm) and [H₂O]<

1 ppm in order to prevent oxidation or hydrolysis; and

(c) heating the mixture under flowing N₂ in conditions of 0.5 to 4 liters per minute to between 1300°

C. and 1500°

C., such that

the luminescent compound that is created comprises Calcium (Ca), Silicon (Si), Nitrogen, Ce³⁺ doping, and a cubic unit cell, wherein the luminescent compound emits orange to red light when the luminescent compound is excited by radiation including one or more wavelengths in a range from ultraviolet to green wavelengths.

13. The method of claim 12, wherein the radiation is ultraviolet (UV) radiation.

14. The method of claim 12, wherein the luminescent Ce compound has an excitation spectrum that peaks in a blue wavelength range.

15. The method of claim 13, wherein the luminescent Ce compound'"'"'s formula comprises CaSiN_2-δ

O_δ

;

Ce³⁺ with 0≦

δ

<

2.

23. The method of claim 12, wherein the light has a peak intensity in a red wavelength range.

24. The method of claim 12, wherein the light has a peak intensity in an orange wavelength range.

25. The method of claim 12, wherein an emission spectrum of the light has a full width at half maximum that includes one or more wavelengths corresponding to orange light.

26. The method of claim 12, wherein an emission spectrum of the light has a full width at half maximum that includes one or more wavelengths corresponding to red light.

27. The method of claim 12, wherein the Ce³⁺ is an emitter.