Phosphor materials and illumination devices made therefrom
This invention provides a phosphor material capable of absorbing primary light and converting that light into white light having a high color rendering index and illumination devices made from the phosphor material. The white light may have a color rendering index of 100 and may be produced with an efficiency of at least 30 lm/w. In one embodiment, the illumination device includes a secondary light source made from a plurality of Group IV semiconductor nanoparticles.
1. A light emitting device comprising:
(a) a primary light source which emits primary light; and
(b) a phosphor material comprising a plurality of nanoparticles, the nanoparticles comprising a Group IV semiconductor, which absorbs at least a portion of the primary light and emits a secondary light, wherein the secondary light or the combination of the secondary light with the primary light comprises a white light.
2. The light emitting device of claim 1 , wherein the primary light is ultraviolet or blue light.
3. The light emitting device of claim 2 , wherein the primary light source is a fluorescent lamp.
4. The light emitting device of claim 1 , wherein the primary light comprises wavelengths of from 320 nm to 480 nm and the secondary light has a lower energy than the primary light.
5. The light emitting device of claim 4 , wherein the primary light source is a blue light emitting diode or an ultraviolet light emitting diode.
6. The light emitting device of claim 1 , wherein the primary light source is an infrared light source and the secondary light has a higher energy than the infrared light.
7. The light emitting device of claim 6 , wherein the primary light source is a red light emitting diode.
8. The light emitting device of claim 6 , wherein the primary light is a halogen lamp or an incandescent lamp.
9. The light emitting device of claim 1 , wherein the nanoparticles have an average particle diameter of from about 1 to about 150 angstroms.
10. The light emitting device of claim 1 , wherein the phosphor material has an emission profile comprising emission peaks in the green to red regions of the visible spectrum.
11. The light emitting device of claim 1 , wherein the phosphor material has an emission profile comprising emission peaks in the blue to red regions of the visible spectrum.
12. The light emitting device of claim 1 , wherein the Group IV semiconductor is silicon.
13. The light emitting device of claim 1 , wherein the Group IV semiconductor is germanium.
14. The light emitting device of claim 1 , wherein the nanoparticles comprises core/shell nanoparticles comprising a Group IV semiconductor core and an inorganic shell.
15. The light emitting device of claim 14 , wherein the inorganic shell comprises ZnS or CdS.
16. The light emitting device of claim 14 , wherein the core comprises silicon and the shell comprises Si 3 N 4 or SiC.
17. The light emitting device of claim 14 , wherein the core comprises silicon and the shell comprises Ge.
18. The light emitting device of claim 14 , wherein the core comprises germanium and the shell comprises Si.
19. The light emitting device of claim 1 , wherein the nanoparticles are dispersed in a binder.
20. The light emitting device of claim 1 , wherein the primary light source comprises an electroluminescent device.
21. The light emitting device of claim 1 , wherein the primary light source comprises an organic light emitting material.
22. The light emitting device of claim 1 , wherein the nanoparticles are dispersed in the organic light emitting material.
23. The light emitting device of claim 1 , wherein the Group IV semiconductor is doped with impurities.
24. The light emitting device of claim 1 , wherein the nanoparticles are embedded in an inorganic binder.
25. The light emitting device of claim 1 , wherein nanoparticles comprising a Group IV semiconductor are SiGe alloy nanoparticles.
26. The light emitting device of claim 1 , wherein the white light has a color rendering index of at least 90.
27. The light emitting device of claim 1 , wherein the device produces white light with an efficiency of at least 30 lm/w.
28. A phosphor material comprising a plurality of domains deposited on an organic film, each domain comprising a plurality of luminescent semiconductor nanoparticles having a substantially monodisperse size distribution.
29. The phosphor material of claim 28 , wherein the organic film has a plurality of luminescent nanoparticles dispersed therein.
30. The phosphor material of claim 29 , wherein the luminescent nanoparticles dispersed in the organic film have a substantially monodisperse size distribution.
31. The phosphor material of claim 29 , wherein the luminescent nanoparticles dispersed in the organic film have a polydisperse size distribution.
32. The phosphor material of claim 28 , wherein the domains have dimensions of no more than about 100 microns.
33. The phosphor material of claim 28 , wherein the plurality of domains comprise a monolayer of nanoparticles.