Coated thioaluminate phosphor particles
View Patent ↗Thioaluminate phosphor particles having a coating comprising or consisting essentially of a nitride, and methods for making such phosphor particles, are disclosed. Phosphor-converted light emitting diodes may comprise such coated phosphor particles. The nitride coatings on the thioaluminate phosphor particles provide a significantly improved barrier to water compared, to an aluminum oxide coating, and extend the operational lifetime of such a phosphor-converted light emitting diode.
1. A luminescent composition of matter comprising:
particles of a sulfide phosphor material characterized by the formula RE 1-w A w M x E y , wherein:
RE is a Rare Earth element or a mixture of Rare Earth elements;
A is selected from the group consisting of Magnesium, Calcium, Strontium, Barium, and mixtures thereof;
M is selected from the group consisting of Aluminum, Gallium, Boron, Indium, Scandium, Lutetium, Yttrium, and mixtures thereof;
E comprises sulfur and optionally at least one of Selenium, Oxygen, and Tellurium;
0≤w≤1.0;
2≤x≤4; and
4≤y≤7;
and a nitride coating layer comprising aluminum nitride, gallium nitride, or a mixture of aluminum nitride and gallium nitride on each particle.
2. The luminescent composition of matter of claim 1 , wherein the nitride coating layer comprises aluminum nitride.
3. The luminescent composition of matter of claim 1 , wherein the nitride coating layer consists essentially of aluminum nitride.
4. The luminescent composition of matter of claim 1 , wherein the nitride coating layer comprises gallium nitride.
5. The luminescent composition of matter of claim 1 , wherein the nitride coating layer consists essentially of gallium nitride.
6. The luminescent composition of matter of claim 1 , wherein the sulfide phosphor material is capable of absorbing blue, violet, or ultraviolet light and in response emitting light having a peak wavelength in the green region of the visible spectrum.
7. The luminescent composition of matter of claim 1 , wherein the nitride coating layer is disposed directly on the sulfide phosphor material.
8. The luminescent composition of matter of claim 1 , wherein each particle comprises an oxide layer disposed between the sulfide phosphor material and the aluminum nitride coating layer.
9. The luminescent composition of matter of claim 1 , wherein each particle comprises at least a second coating layer disposed on the nitride coating layer.
10. The luminescent composition of matter of claim 9 , wherein the second coating layer is an oxide layer.
11. The luminescent composition of matter of claim 1 , wherein RE is Europium.
12. A light emitting device comprising:
a light emitting diode that emits primary light; and
particles of a sulfide phosphor material characterized by the formula RE 1-w A w M x E y , wherein:
RE is a Rare Earth element or a mixture of Rare Earth elements;
A is selected from the group consisting of Magnesium, Calcium, Strontium, Barium, and mixtures thereof;
M is selected from the group consisting of Aluminum, Gallium, Boron, Indium, Scandium, Lutetium, Yttrium, and mixtures thereof;
E comprises sulfur and optionally at least one of Selenium, Oxygen, and Tellurium;
0≤w≤1.0;
2≤x≤4; and
4≤y≤7;
wherein the sulfide phosphor material is capable of absorbing at least a portion of the primary light and in response emitting secondary light having a wavelength longer than a wavelength of the primary light, and each particle of the sulfide phosphor material comprises a nitride coating layer comprising aluminum nitride, gallium nitride, or a mixture of aluminum nitride and gallium nitride.
13. The light emitting device of claim 12 , wherein the nitride coating layer comprises aluminum nitride.
14. The light emitting device of claim 12 , wherein the nitride coating layer consists essentially of aluminum nitride.
15. The light emitting device of claim 12 , wherein the nitride coating layer comprises gallium nitride.
16. The light emitting device of claim 12 , wherein the nitride coating layer consists essentially of gallium nitride.
17. The light emitting device of claim 12 , wherein the secondary light has a peak wavelength in the green region of the visible spectrum.
18. The light emitting device of claim 12 , wherein RE is Europium.
19. The light emitting device of claim 18 , wherein the primary light is blue light.
20. The light emitting device of claim 19 , wherein the secondary light has a peak wavelength in the green region of the visible spectrum.