Light-emitting device with light scatter tuning to control color shift
A system and methods for light-emitting diode (LED) devices with a dimming feature that can tailor a color point shift in the light color temperature of a scattering/transparent layer to enlarge a dim to warm range are disclosed herein. A light-emitting device may include a wavelength converting structure configured to receive light from a light emitting semiconductor structure and an adjacent light scattering structure. The light scattering structure may comprise a plurality of scattering particles with a lower refractive index (RI) than the RI of the matrix material in which the scattering particles are disposed. The wavelength converting structure may include a red phosphor and a green phosphor such that to adjust overlap between green emission and absorption by the red phosphor to correspondingly adjust scattering and magnitude of color shift. In an embodiment, the light scattering structure may be integrated in the wavelength converting structure.
1. A light-emitting device configured to produce a white light comprising:
a light emitting semiconductor structure configured to emit blue light;
a wavelength converting structure disposed in a path of the light emitted by the light emitting semiconductor structure and comprising a green phosphor material, a broad red phosphor material, and a narrow red phosphor material; and
a light scattering structure arranged with respect to the wavelength converting structure to scatter light back toward the wavelength converting structure; the light scattering structure configured to scatter more light as the temperature of the light scattering structure increases;
in operation with the light scattering structure at 25° C., the white light output of the light-emitting device has a correlated color temperature of less than 2500K and with the light scattering structure at 85° C., the white light output of the light-emitting device has a correlated color temperature of greater than 2700K.
2. The light-emitting device of claim 1 wherein the green phosphor material comprises (Lu,Y) 3 (Al,Ga) 5 O 12 :Ce 3+ or (Ba,Sr) 2 SiO 4 :Eu 2+ .
3. The light-emitting device of claim 1 , wherein the narrow red phosphor material comprises SLA phosphor Sr(LiAl 3 N 4 ):Eu 2+ .
4. The light-emitting device of claim 1 , wherein the broad red phosphor material comprises (Ca,Sr)AlSiN 3 :Eu 2+ or (Ga,Sr,Ba) 2 Si 5 N 8 :Eu 2+ .
5. The light-emitting device of claim 1 , wherein
the green phosphor material comprises (Lu,Y) 3 (Al,Ga) 5 O 12 :Ce 3+ or (Ba,Sr) 2 SiO 4 :Eu 2+ ;
the narrow red phosphor material comprises SLA phosphor Sr(LiAl 3 N 4 ):Eu 2+ ; and
the broad red phosphor material comprises (Ca,Sr)AlSiN 3 :Eu 2+ or (Ga,Sr,Ba) 2 Si 5 N 8 :Eu 2+ .
6. The light-emitting device of claim 1 , wherein the second material of the light scattering structure comprises silicone and the first material of the light scattering structure comprises MgF 2 .
7. The light-emitting device of claim 1 , wherein the second material of the light scattering structure comprises silicone and the first material of the light scattering structure comprises porous silica.
8. The light-emitting device of claim 1 , wherein the light scattering structure comprises a plurality of scattering particles of a first material having a first index of refraction n 1 dispersed in a second material having a second index of refraction n 2 , (n 2 −n 1 ) having a larger magnitude at 25° C. than at 85° C., and
a concentration of scattering particles in the second material and a change in the value of (n 2 −n 1 ) between 25° C. and 85° C. such that in operation with the light scattering structure at 25° C., the white light output of the light-emitting device has a correlated color temperature of less than 2500K and with the light scattering structure at 85° C., the white light output of the light-emitting device has a correlated color temperature of greater than 2700K.
9. The light emitting device of claim 1 , wherein
the narrow red phosphor material comprises SLA phosphor Sr(LiAl 3 N 4 ):Eu 2+ ; and
the broad red phosphor material comprises (Ca,Sr)AlSiN 3 :Eu 2+ or (Ga,Sr,Ba) 2 Si 5 N 8 :Eu 2+ .
10. The light emitting device of claim 1 , wherein in operation with the light scattering structure at 25° C., the white light output of the light-emitting device has a correlated color temperature of about 2000K and with the light scattering structure at 85° C., the white light output of the light-emitting device has a correlated color temperature of greater than 3000K.
11. The light emitting device of claim 1 , wherein in operation with the light scattering structure at 25° C., the white light output of the light-emitting device has a correlated color temperature between 2000K and 2200K and with the light scattering structure at 85° C., the white light output of the light-emitting device has a correlated color temperature of greater than 2700K.
12. The light emitting device of claim 1 , wherein in operation with the light scattering structure at 25° C., the white light output of the light-emitting device has a correlated color temperature between 1500K and 2500K and with the light scattering structure at 85° C., the white light output of the light-emitting device has a correlated color temperature of greater than 2700K.
13. A light-emitting device configured to produce a white light comprising:
a light emitting semiconductor structure configured to emit blue light when a drive current is applied to the light emitting semiconductor structure;
a wavelength converting structure disposed in a path of the light emitted by the light emitting semiconductor structure and comprising a green phosphor material, a broad red phosphor material, and a narrow red phosphor material;
a light scattering structure arranged with respect to the wavelength converting structure to scatter light back toward wavelength converting structure; the light scattering structure configured so that as the drive current is increased the light scattering structure scatters more light;
in operation when a drive current of approximately 30 mA is applied to the light emitting semiconductor structure, the white light output of the light-emitting device has a correlated color temperature of less than 2500K and when a drive current of approximately 250 mA is applied to the light emitting semiconductor structure, the white light output of the light-emitting device has a correlated color temperature of greater than 2700K.
14. The light-emitting device of claim 13 wherein the green phosphor material comprises (Lu,Y) 3 (Al,Ga) 5 O 12 :Ce 3+ or (Ba,Sr) 2 SiO 4 :Eu 2+ .
15. The light-emitting device of claim 13 , wherein the narrow red phosphor material comprises SLA phosphor Sr(LiAl 3 N 4 ):Eu 2+ .
16. The light-emitting device of claim 13 , wherein the broad red phosphor material comprises (Ca,Sr)AlSiN 3 :Eu 2+ or (Ga,Sr,Ba) 2 Si 5 N 8 :Eu 2+ .
17. The light-emitting device of claim 13 , wherein
the green phosphor material comprises (Lu,Y) 3 (Al,Ga) 5 O 12 :Ce 3+ or (Ba,Sr) 2 SiO 4 :Eu 2+ ;
the narrow red phosphor material comprises SLA phosphor Sr(LiAl 3 N 4 ):Eu 2+ ; and
the broad red phosphor material comprises (Ca,Sr)AlSiN 3 :Eu 2+ or (Ga,Sr,Ba) 2 Si 5 N 8 :Eu 2+ .
18. The light emitting device of claim 13 , wherein in operation when the drive current is approximately 30 mA, the white light output of the light-emitting device has a correlated color temperature between 2000K and 2200K and when the drive current is 250 mA, the white light output of the light-emitting device has a correlated color temperature of greater than 2700K.
19. The light emitting device of claim 13 , wherein in operation when the drive current is approximately 30 mA, the white light output of the light-emitting device has a correlated color temperature between 1500K and 2500K and when the drive current is approximately 250 mA, the white light output of the light-emitting device has a correlated color temperature of greater than 2700K.
20. A light-emitting device configured to produce a white light comprising:
a light emitting semiconductor structure configured to emit blue light;
a wavelength converting structure disposed in a path of the light emitted by the light emitting semiconductor structure and comprising a first phosphor material configured to emit green light, a second phosphor material configured to emit red light, and a third phosphor material comprising SLA phosphor Sr(LiAl 3 N 4 ):Eu 2+ ; and
a light scattering structure arranged with respect to the wavelength converting structure to scatter light back toward the wavelength converting structure; the light scattering structure configured to scatter more light as the temperature of the light scattering structure increases;
in operation with the light scattering structure at 25° C., the white light output of the light-emitting device has a correlated color temperature of less than 2500K and with the light scattering structure at 85° C., the white light output of the light-emitting device has a correlated color temperature of greater than 2700K.