Phosphors with narrow green emission
Green emitting phosphors have the empirical composition RE 1−w A w M x E y , where RE may be one or more Rare Earth elements (for example, Eu or Gd), A may be one or more elements selected from the group Mg, Ca, Sr, or Ba, M may be one or more elements selected from the group Al, Ga, B, In, Sc, Lu or Y, E may be one or more elements selected from the group S, Se, O, or Te, w is greater than or equal to zero, or greater than or equal to 0.01, or greater than or equal to 0.05, and less than or equal to about 0.8, 2≤x≤4, and 4≤y≤7.
1. A light emitting device comprising:
a light emitting diode that emits primary light; and
a RE 1−w A w M x E y phosphor material 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;
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, or Selenium, or Sulfur and Selenium, and optionally Oxygen, Tellurium, or Oxygen and Tellurium;
0.01≤w≤0.8;
2≤x≤4; and
4≤y≤7.
2. The light emitting device of claim 1 , wherein RE is Europium.
3. The light emitting device of claim 1 , wherein 0.30≤w≤0.66.
4. The light emitting device of claim 1 , wherein the RE 1−w A w M x E y phosphor has exclusively an EuM 2 E 4 pseudoorthorhombic crystal structure.
5. The light emitting device of claim 1 , wherein the RE 1−w A w M x E y phosphor has a mixture of predominantly an EuM 2 E 4 pseudoorthorhombic crystal structure and one or more binary chalcogenide crystal structures.
6. The light emitting device of claim 1 , wherein the light emitting diode is a laser diode.
7. The light emitting device of claim 1 , wherein the primary light has a wavelength between about 380 nanometers and about 500 nanometers.
8. The light emitting device of claim 7 , wherein the primary light is blue light.
9. The light emitting device of claim 1 , wherein the secondary light has a wavelength between about 475 nanometers and about 560 nanometers.
10. The light emitting device of claim 1 , wherein:
RE is Europium; and
0.30≤w≤0.66.
11. The light emitting device of claim 10 , wherein the RE 1−w A w M x E y phosphor has exclusively an EuM 2 E 4 pseudoorthorhombic crystal structure.
12. The light emitting device of claim 10 , wherein the primary light is blue light.
13. The light emitting device of claim 1 , comprising a second phosphor material capable of absorbing at least a portion of the primary light and in response emitting red light; wherein the combined emission from the light emitting device of unabsorbed primary light, the secondary light, and the red light appears white to a human observer with normal color vision.
14. The light emitting device of claim 13 , wherein:
RE is Europium; and
0.30≤w≤0.66.
15. The light emitting device of claim 14 , wherein the RE 1−w A w M x E y phosphor has exclusively an EuM 2 E 4 pseudoorthorhombic crystal structure.
16. The light emitting device of claim 14 , wherein the primary light is blue light.
17. The light emitting device of claim 16 , wherein the secondary light has a wavelength between about 475 nanometers and about 560 nanometers.