Light emitting device with porous structure to enhance color point shift as a function of drive current

1. A light emitting device (LED), comprising:

a light emitting layer; and

a wavelength converting material comprising a plurality of pores and configured to absorb light emitted by the light emitting layer and in response emit light of a longer wavelength; and

a fill material disposed in at least one of the pores in the wavelength converting material, such that one or more of the pores is each entirely filled by fill material if the wavelength converting material is at a first temperature, and only partially filled by fill material if the wavelength converting material is at a second temperature.

2. The LED of claim 1 , wherein the absolute value of the ratio of the coefficient of thermal expansion of the fill material to the coefficient of thermal expansion of the phosphor material is at least two.

3. The LED of claim 1 , wherein the phosphor material comprising the plurality of pores further comprises one of a ceramic phosphor element or phosphor particles in a transparent or translucent binder or matrix.

4. The LED of claim 1 , wherein one or more of the pores is each partially filled with the fill material, wherein remaining volume of the one or more partially filled pores comprises gas or vacuum.

5. The LED of claim 1 , wherein the fill material is one of silicone, epoxy, urethane, and mixtures of one or more of silicone, epoxy and urethane.

6. The LED of claim 1 , wherein the pores have diameters ranging between one 10 nm to 10 μm, 10 nm to 0.5 μm, or 50 nm to 0.5 μm.

7. The LED of claim 1 , wherein the phosphor material has a porosity ranging between one of 0 to 0.8, 0 to 0.5, 0 to 0.1, 0 to 0.05, 0.01 to 0.1, and 0.01 to 0.05.

8. The LED of claim 1 , wherein:

the light emitting semiconductor diode structure has a first surface, a second surface opposite the first surface and a plurality of side surfaces,

the phosphor material has a first surface, a second surface opposite the first surface, and a plurality of side surfaces,

the first surface of the phosphor material is disposed adjacent the first surface of the light emitting semiconductor diode structure, and

pores formed in the first surface of the phosphor material contain a silicone having a lower molecular weight or lower index than pores formed in the second surface and side surfaces of the phosphor material.

9. The LED of claim 1 , wherein the pores are formed uniformly through an entire thickness of the phosphor material or graded in porosity through at least a portion of the thickness of the phosphor material.

10. The LED of claim 1 , wherein:

the plurality of pores include pores formed in a surface of the phosphor material that has pores that at least one of dead end, cross link to pores formed in a surface of the phosphor material, and throat from one surface to at least one other surface of the phosphor material, and pores that are not formed in, and

the one or more pores that contain the fill material are at least one of the pores.

11. The LED of claim 1 , comprising:

a coating material disposed as a coating on the phosphor material, the coating comprising a second plurality of pores; and

a second fill material disposed in the pores in the coating;

wherein an absolute value of a ratio of a coefficient of thermal expansion of the second fill material to a coefficient of thermal expansion of the coating material is at least two.

12. A light emitting device (LED) comprising:

a light emitting semiconductor diode structure comprising a light emitting active layer disposed between an n-layer and a p-layer; and

a phosphor material having a first surface adjacent the light emitting semiconductor diode structure and a second surface opposite the first surface of the phosphor material; and

a coating material disposed as a coating on and in direct contact with the second surface of the phosphor material, the coating material including a plurality of pores, at least one of the plurality of pores containing a fill material such that the at least one pore is each entirely filled by fill material if the phosphor material is at a first temperature, and only partially filled by fill material if the phosphor material is at a second temperature.

13. The LED of claim 12 , wherein the phosphor material comprises one of a layer of phosphor particles and a ceramic phosphor element.

14. The LED of claim 12 , wherein the phosphor material further comprises a plurality of other pores, at least one of the plurality of other pores being filled with the fill material.

15. The LED of claim 12 , wherein the coating has an index of refraction that matches that of the phosphor material on which the coating is disposed.

16. The LED of claim 12 , wherein the phosphor material comprises one of red emitting K 2 (Ti,Si)F 6 :Mn having an index of refraction of approximately 1.4, yellow-green emitting garnets having an index of refraction of approximately 1.8, and orange-red emitting nitridosilicates having an index of refraction above 2.0, and the coating is formed from a material comprising one of silica having an index of refraction of approximately 1.4, AlOX having an index of refraction of approximately 1.8, and SiON or Si 3 N 4 having an index of refraction above 2.0.

17. The LED of claim 12 , wherein the fill material is a silicone material.

18. The LED of claim 12 , wherein the one or more of the pores is each entirely filled by fill material if the phosphor material is at a temperature of at least 125° C. and only partially filled by fill material if the phosphor material is at a temperature of 30° C.

19. The LED of claim 12 , wherein the pores have diameters ranging between one of 10 nm to 10 μm, 10 nm to 0.5 μm, or 50 nm to 0.5 μm.

20. The LED of claim 12 , wherein phosphor material has a porosity ranging between one of 0 to 0.8, 0 to 0.5, 0 to 0.1, 0 to 0.05, 0.01 to 0.1, and 0.01 to 0.05.