Ultra-smooth sidewall pixelated array LEDs
Pixelated array light emitters are formed with closely-spaced pixels having ultra-smooth sidewalls. In methods for making such pixelated array light emitters, a converter layer of phosphor particles dispersed in a binder is disposed on a carrier, and then singulated by saw cuts or similar methods to form an array of phosphor pixels. The binder is fully cured prior to singulation of the converter layer. Further, the carrier is rigid rather than flexible. As a consequence of fully curing the binder and of using a rigid carrier to support the converter layer, singulation results in phosphor pixels having smooth side walls. The array of phosphor pixels is subsequently attached to a corresponding array of LEDs with an adhesive layer, separate from the binder used to form the converter layer. The pixel sidewalls may be formed with controlled morphology, for example at acute or obtuse angles with respect to the carrier.
1. A wavelength converter structure comprising:
a carrier substrate;
a converter layer disposed on a surface of the carrier substrate and comprising phosphor particles dispersed in a fully cured binder;
an adhesive layer, separate from the binder in the converter layer, deposited on the converter layer and;
trenches formed through the adhesive layer and the converter layer to define a plurality of spaced-apart phosphor pixels each comprising a portion of the adhesive layer, the trenches defining side walls of the phosphor pixels having a roughness parameter Ra of less than or equal to about 100 nanometers.
2. The wavelength converter structure of claim 1 , wherein the side walls of the phosphor pixels are oriented at acute or obtuse angles with respect to the surface of the carrier substrate.
3. The wavelength converter structure of claim 1 , wherein the binder is or comprises a silicone.
4. The wavelength converter structure of claim 1 comprising a plurality of LEDs each attached to a corresponding phosphor pixel by the portion of the adhesive layer on the phosphor pixel.
5. The wavelength converter structure of claim 1 , wherein the roughness parameter Ra is less than or equal to about 10 nanometers.
6. The wavelength converter structure of claim 1 , wherein:
the side walls of the phosphor pixels are oriented at acute or obtuse angles with respect to the surface of the carrier substrate;
the binder is or comprises a silicone; and
the adhesive is or comprises a silicone.
7. The wavelength converter structure of claim 1 , wherein the adhesive layer has a thickness of about 100 nanometers to about 5 microns.
8. The wavelength converter structure of claim 1 , further comprising a reflective or scattering layer disposed between the phosphor pixels.
9. The wavelength converter structure of claim 8 , wherein the reflective or scattering layer comprises TiO 2 particles embedded in silicone.
10. The wavelength converter structure of claim 8 , wherein the reflective or scattering layer comprises one or more Distributed Bragg Reflector structures each having a stack of alternating layers of high and low refractive index material.
11. The wavelength converter structure of claim 8 , wherein the reflective or scattering layer comprises one or more reflective layers.
12. The wavelength converter structure of claim 8 , wherein the reflective or scattering layer is separated by phosphor pixels, and is not directly disposed on light output surfaces of the phosphor pixels.
13. The wavelength converter structure of claim 1 , wherein the phosphor pixels are spaced apart from each other at a distance less than or equal to about 20 microns.
14. The wavelength converter structure of claim 2 , wherein the side walls of the phosphor pixels oriented at acute or obtuse angles extend from light input surfaces of the phosphor pixel to light output surfaces of the phosphor pixel in straight lines.
15. The wavelength converter structure of claim 2 , wherein each phosphor pixel is tapered with a light output surface opposite a light input surface smaller in area than the light output surface and in direct contact with the adhesive layer.
16. The wavelength converter structure of claim 1 , wherein each of the trenches has a width of about 5 microns to 200 microns.
17. The wavelength converter structure of claim 16 , wherein the trenches are tapered and the width of the trenches is a narrowest width of the trenches, and the trenches are spaced apart from each other at a distance from about 5 microns to about 200 microns.
18. The wavelength converter structure of claim 1 , wherein the converter layer has a thickness of about 50 microns to about 200 microns.
19. The wavelength converter structure of claim 1 , wherein the phosphor pixels are spaced apart from each other at a distance of about 5 microns to 200 microns.
20. The wavelength converter structure of claim 6 , wherein the adhesive layer is fully cured.