Nanocrystalline based phosphors and photonic structures for solid state lighting

• US 6,734,465 B1
• Filed: 11/19/2002
• Issued: 05/11/2004
• Est. Priority Date: 11/19/2001
• Status: Expired due to Fees

• Current Assignee: Nanocrystals Technology LP
• Original Assignee: Nanocrystals Technology LP
• Inventors: Bhargava, Rameshwar Nath, Taskar, Nikhil R.
• Primary Examiner(s): Nelms, David
• Assistant Examiner(s): HO, TU TU V
• Application Number:
  US10/299,410
• Time in Patent Office: 539 Days
• Field of Search: 257/80, 257/100
• US Class Current: 257/80
• CPC Class Codes: H01L 33/44 characterised by the coatings, e.g. passivation layer or anti-reflective coating
• CPC Class Codes: H01L 33/502 Wavelength conversion materials
• CPC Class Codes: H01L 33/54 having a particular shape

Abstract

A photonic structure for “white” light generation by phosphors under the excitation of a LED. The photonic structure mounts the LED and an optically transparent matrix having dispersed therein phosphors which will emit light under the excitation of the radiation of the LED. The transparent matrix may include nanoparticles for matching the index of refraction of the material of the matrix to that of the light generating phosphors. The matrix material may be readily formed by molding and formed into a variety of shapes including lenses for focusing the emitted light. A large number of the photonic structures may be arranged on a substrate to provide even illumination or other purposes. The phosphors dispersed in the matrix are preferably nanocrystalline.

Claims

1. A photonic structure for emission of white light under excitation by an LED, comprising:

a) a radiation emitting diode;

b) an optically transparent matrix material disposed so as to intercept the light emitted by said diode; and

c) nanocrystalline phosphors dispersed within said matrix material, that will emit light upon excitation by the radiation of the diode.

2. The photonic structure as claimed in claim 1 wherein the nanocrystalline phosphors comprise individual nanoparticles having an average diameter of less than 20 nm.

3. The photonic structure as claimed in claim 1 wherein the nanocrystalline phosphors comprise optically-nonscattering agglomerates of individual nanoparticles having an average diameter of less than 40 nm.

4. The photonic structure as claimed in claim 1 wherein the nanocrystalline phosphors comprise optically-scattering agglomerates of individual nanoparticles having an average diameter of greater than 40 nm and the matrix material has a index of refraction generally equal to that of the optically-scattering agglomerates of individual nanoparticles.

5. The photonic structure as claimed in claim 1 wherein the optically transparent matrix material surrounds said diode.

6. The photonic structure as claimed in claim 1 wherein the matrix material is selected from the group consisting of:

epoxy, silica, silica with a polymer, alumina, silicone and silicone-epoxy hybrids.

7. The photonic structure as claimed in claim 1 wherein the optically transparent matrix material includes a dispersion of non-light emitting nanoparticles for raising the refractive index of the matrix material.

8. The photonic structure as claimed in claim 1 further including a substrate to which multiple diodes are mounted.

9. The photonic structure as claimed in claim 1 wherein the diodes and the matrix are disposed within a light reflector.

10. The photonic structure as claimed in claim 1 wherein the diodes emit 370-470 nm radiation.

11. The photonic structure as claimed in claim 1 wherein the nanocrystalline phosphors comprise separate phosphors that emit red, green and blue light upon excitation by the radiation of the diode.

12. The photonic structure as claimed in claim 1 wherein the diode is at least one of a blue emitting diode and a UV emitting diode.

13. The photonic structure as claimed in claim 1 wherein the nanocrystalline phosphors comprise at least one of:

yttrium aluminum garnet doped with cerium and terbium aluminum garnet doped with cerium.

14. The photonic structure as claimed in claim 13 wherein the diode is a blue emitting diode.

15. The photonic structure as claimed in claim 1 further including a reflector disposed proximate to at least one of said radiation emitting diode and said optically transparent matrix material.

16. The photonic structure as claimed in claim 15 wherein said reflector also functions as an electrical connection to said radiation emitting diode.

17. The photonic structure as claimed in claim 1 wherein the diode and the nanocrystalline phosphors comprise complementary colors.

18. The photonic structure as claimed in claim 1 wherein the nanocrystalline phosphors comprise multiple wavelength phosphors.

19. A photonic structure for emission of white light under excitation by an LED, comprising:

a) a substrate;

b) a plurality of radiation emitting diodes, disposed on said substrate;

c) an optically transparent matrix material disposed so as to intercept the light emitted by said diodes; and

d) nanocrystalline phosphors dispersed within said matrix material, that will emit light upon excitation by the radiation of the diodes.

20. The photonic structure as claimed in claim 19 wherein the optically transparent matrix material includes a dispersion of non-light emitting nanoparticles for raising the refractive index of the matrix material.

21. The photonic structure as claimed in claim 19 wherein the nanocrystalline phosphors comprise separate phosphors that emit red, green and blue light upon excitation by the radiation of the diode.

22. The photonic structure as claimed in claim 19 wherein matrix material forms lenses.

23. A photonic structure for emission of white light under excitation by an LED, comprising:

a) a radiation emitting diode;

b) an optically transparent matrix material disposed so as to intercept the light emitted by said diode;

c) phosphors dispersed within said matrix material, that will emit light upon excitation by the radiation of the diode; and

d) non light emitting non-scattering nanoparticles dispersed within said matrix material so as to match the index of refraction of the matrix material to that of the phosphors.

24. The photonic structure as claimed in claim 23 wherein non light emitting non-scattering nanoparticles dispersed within said matrix material have an agglomerate size of less than 40 nm.