Luminescent particles, methods of identifying same and light emitting devices including the same

• US 9,464,225 B2
• Filed: 11/17/2009
• Issued: 10/11/2016
• Est. Priority Date: 11/17/2008
• Status: Active Grant

• Current Assignee: Creeled Incorporated
• Original Assignee: CREE Incorporated (Wolfspeed, Inc.)
• Inventors: Collins, Brian Thomas, Le Toquin, Ronan P.
• Primary Examiner(s): Choi, Ling
• Assistant Examiner(s): Miller, David L
• Application Number:
  US12/619,838
• Publication Number:
  US 20100127613A1
• Time in Patent Office: 2,520 Days
• Field of Search: 252/586, 252/301.4 R, 252/301.4 F, 252/301.6 F, 252/301.6 R, 313/503, 313/486, 356/311, 362/231, 362/260, 362/293, 362/800
• US Class Current: 1/1
• CPC Class Codes: C09K 11/0883 Arsenides; Nitrides; Phosphides
• CPC Class Codes: C09K 11/77347 Silicon Nitrides or Silicon Oxynitrides
• CPC Class Codes: C09K 11/77348 Silicon Aluminium Nitrides or Silicon Aluminium Oxynitrides

Abstract

A luminescent particle includes a luminescent compound that is configured to perform a photon down conversion on a portion of received light and a reflectance reducing outer surface of the luminescent particle that is operable to increase the portion of received light that is absorbed in the luminescent particle.

Claims

1. A plurality of luminescent particles, each of the luminescent particles comprising:

an interior portion comprising a luminescent compound comprising a nitride that is configured to perform a photon down conversion on a portion of received light;

a passivating region on an outer surface of the interior portion and operable to inhibit reactions involving the luminescent compound,

wherein the passivating region comprises nitrogen, the nitrogen being present at a reduced percentage compared to the interior portion of the luminescent particle; and

a reflectance reducing outer surface of each luminescent particle that is configured to increase the portion of received light that is absorbed in the luminescent particle, wherein the reflectance reducing outer surface includes a substantially continuous contoured surface,

wherein the plurality of luminescent particles comprise a first diffuse reflectance of from 31.1% to 34.2% at a dominant wavelength of light of about 450 nm.

2. A light emitting device comprising:

the plurality of luminescent particles of claim 1; and

a light emitting source.

3. The light emitting device according to claim 2,

wherein the plurality of luminescent particles are dispersed within a silicone encapsulant, 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 luminescent particles absorb 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.

4. The light emitting device according to claim 2,

wherein a plurality of first luminescent particles including the plurality of luminescent particles include a first size range and the first diffuse reflectance at the dominant wavelength of light,

where a plurality of second luminescent particles not including the plurality of luminescent particles include a second size range that is similar to the first size range and a second diffuse reflectance at the dominant wavelength of light.

5. The plurality of luminescent particles according to claim 1 comprising a D50 particle size of from 9.4 microns to 12.8 microns.

6. The plurality of luminescent particles according to claim 1, wherein the luminescent compound is selected from the group consisting of Ca_1-xSr_xAlSiN₃, Ca₂Si₅N₈, Sr₂Si₅N₈, Ba₂Si₅N₈, BaSi₇N₁₀, BaYSi₄N₇, Ca_1.5Si₉A1₃N₁₆, and CaSiN₂, where 0≦

x≦

1.

7. The plurality of luminescent particles according to claim 6, wherein the luminescent compound is Ca_1-xSr_xAlSiN₃, where 0≦

x≦

1.

8. The light emitting device according to claim 2,

wherein the plurality of luminescent particles are mixed with an encapsulant,

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 plurality of luminescent particles absorb at least some of the light emitted from the light emitting source and emit light having a maximum emission at a wavelength in a range of about 500 to about 700 nm, the plurality of luminescent particles being red-emitting luminescent particles.

9. The light emitting device according to claim 8, wherein a concentration of the red-emitting luminescent particles mixed with the encapsulant is about 6 wt.%.

10. The light emitting device according claim 9, further comprising a plurality of yellow-emitting luminescent particles, wherein a weight ratio of the yellow-emitting luminescent particles to the red-emitting luminescent particles is about 4.2.