Light emitting device with phase changing off state white material and methods of manufacture
View Patent ↗Light emitting devices (LEDs) are described herein. An LED includes a light emitting semiconductor structure, a wavelength converting material and an off state white material. The light emitting semiconductor structure includes a light-emitting active layer disposed between an n-layer and a p-layer. The wavelength converting material has a first surface adjacent the light emitting semiconductor structure and a second surface opposite the first surface. The off state white material is in direct contact with the second surface of the wavelength converting material and includes multiple core-shell particles disposed in an optically functional material. Each of the core-shell particles includes a core material encased in a polymer or inorganic shell. The core material includes a phase change material.
1. A light emitting device (LED) comprising:
a light emitting semiconductor structure comprising a light-emitting active layer disposed between an n-layer and a p-layer;
a wavelength converting material having a first surface adjacent the light emitting semiconductor structure and a second surface opposite the first surface; and
an off state white material in direct contact with the second surface of the wavelength converting material, the off state white material comprising a plurality of core-shell particles disposed in an optically functional material, each of the core shell particles comprising a core material that includes a phase change material encased in a polymer or inorganic shell.
2. The LED of claim 1 , wherein the phase change material is selected from the group consisting of a paraffin and a deuterated paraffin analog.
3. The LED of claim 1 , wherein the off state white material comprises between 5 percent and 40 percent by volume fraction of the core-shell p articles.
4. The LED of claim 1 , wherein the core material further comprises silicone in a ratio of 50% to 90% silicone to the phase change material by weight.
5. The LED of claim 1 , wherein the polymer or inorganic shell is one of melamine formaldehyde based or silica based.
6. The LED of claim 1 , wherein the shell is a polymer shell and is deuterated.
7. The LED of claim 1 , wherein the phase change material has a melting point of between 43° C. and 100° C.
8. The LED of claim 1 , wherein the phase change material is one of deuterated tricosane, deuterated docosane, deuterated hexacosane, and deuterated octacosane.
9. The LED of claim 1 , wherein the light emitting semiconductor structure is a blue light emitting semiconductor structure.
10. The LED of claim 9 , wherein the wavelength converting material comprises one of a yellow-emitting phosphor material or green-emitting and red-emitting phosphor materials.
11. The LED of claim 1 , wherein each of the plurality of particles has a diameter of between 1 μm and 50 μm.
12. The LED of claim 1 , wherein the optically functional material comprises silicone and the plurality of core-shell particles are dispersed in the silicone.
13. The LED of claim 1 , wherein the optically functional material comprises a temperature and light resistant matrix and the plurality of core-shell particles are embedded in the temperature and light resistant matrix.
14. The LED of claim 1 , wherein the off state white material is disposed on the wavelength converting material as a layer or a film.
15. The LED of claim 1 , wherein the optically functional material forms a lens.