Methods and devices using high efficiency alkaline earth metal thiogallate-based phosphors
View Patent ↗The present invention provides a light emitting device comprising: a light output; a light source that produces light having a wavelengths of 530 nm or less; and a wavelength transformer located between the light source and the light output, where the wavelength transformer comprises Sr 1-x Ca x Ga 2 S 4 : yEu 2+ ·zGa 2 S 3 , where x is 0.0001 to 1, y is a value defining sufficient Eu 2+ to provide luminescent emission, and z is 0.0001 to 0.2 based on the mole amount of Sr x Ca 1-x Ga 2 S 4 , and where the wavelength transformer effectively increases the light at the light output, the light having a wavelength between 535 nm and 560 nm.
1. A light emitting device comprising:
a light output;
a light source producing light including wavelengths of 530 nm or less; and
a wavelength transformer located between the light source and the light output, comprising Sr 1-x Ca x Ga 2 S 4 :yEu 2+ ·zGa 2 S 3 , wherein:
x is 0.0001 to 1;
y is a value defining sufficient Eu 2+ to provide luminescent emission;
z is 0.0001 to 0.2 based on the mole amount of Sr x Ca 1-x Ga 2 S 4 ; and
the wavelength transformer effectively increases the light at the light output, the light having a wavelength between 535 nm and 560 nm.
2. The light emitting device of claim 1 , wherein z is 0.001 to 0.2.
3. The light emitting device of claim 1 , wherein z is 0.001 to 0.1.
4. The light emitting device of claim 1 , wherein y is 0.001 to 0.1 based on the mole amount of Sr 1-x Ca x Ga 2 S 4 .
5. The light emitting device of claim 4 , wherein y is 0.01 to 0.08.
6. The light emitting device of claim 4 , wherein y is 0.01 to 0.04.
7. The light emitting device of claim 1 , wherein the phosphor has an emission peak of 535 nm to 560 nm.
8. The light emitting device of claim 7 , wherein the emission peak has a bandwidth of 50 nm or less under excitation with an emission source at 440 nm±40 nm.
9. A method of making a strontium calcium thiogallate phosphor of formula Sr 1-x Ca x Ga 2 S 4 :yEu 2+ ·zGa 2 S 3 , wherein:
x is 0.0001 to 1;
y is a value defining sufficient Eu 2+ to provide luminescent emission; and
z is 0.0001 to 0.2 based on the mole amount of Sr 1-x Ca x Ga 2 S 4 , the method comprising:
forming a composition of sulfate salts of gallium, divalent europium, calcium and, if x is not 1, strontium; and
firing the composition under hydrogen sulfide.
10. The method of claim 9 , wherein z is 0.001 to 0.2.
11. The method of claim 9 , wherein an amount of gallium is tuned to the range of 0.1 to 7% in excess of the stoichiometric amount of Sr x Ca 1-x Ga 2 S 4 :yEu 2+ .
12. The method of claim 9 , further comprising:
a second firing of the composition following the fixing under hydrogen sulfide.
13. The method of claim 12 , wherein the firing under hydrogen sulfide is conducted at 500 to 850 degrees C.
14. The method of claim 13 , wherein the second firing is conducted at 750 to 950 degrees C.
15. The method of claim 13 , wherein the product of the firing under hydrogen sulfide is ground prior to the second firing.
16. The method of claim 9 , wherein z is 0.001 to 0.1.
17. The method of claim 9 , wherein y is 0.001 to 0.1 based on the mole amount of Sr 1-x Ca x Ga 2 S 4 .
18. The method of claim 17 , wherein y is 0.01 to 0.08.
19. The method of claim 18 , wherein y is 0.01 to 0.04.
20. The method of claim 9 , wherein the phosphor has an emission peak of 535 nm to 560 nm.
21. The method of claim 20 , wherein the emission peak has a bandwidth of 50 nm or less under excitation with an emission source at 440 nm±40 nm.