Pixelated LED array with optical elements
The pcLED pixels in a phosphor-converted LED array each comprise an optical element on the light-emitting surface above the phosphor layer. In methods for making such pixelated LED arrays, a thin layer of a sacrificial phosphor carrier substrate is retained as the optical element on the output surface of the phosphor pixels upon completion of the fabrication process.
1. A light emitting device comprising:
a plurality of semiconductor light emitting diode structures arranged in an array, each semiconductor light emitting diode structure comprising a first surface, an oppositely positioned second surface, and side surfaces perpendicular to and connecting the first and second surfaces;
a plurality of phosphor pixels each comprising a first surface, an oppositely positioned second surface, and side surfaces perpendicular to and connecting the first and second surfaces, the side surfaces being planar, each phosphor pixel having its second surface attached to the first surface of a corresponding semiconductor light emitting diode structure, each phosphor pixel having a thickness of about 20 microns to about 500 microns perpendicular to the first surface of the semiconductor light emitting diode structure and a longest dimension parallel to a plane of the array of about 5 microns to about 200 microns, adjacent phosphor pixels spaced apart from each other by a distance of about 5 microns to about 200 microns measured parallel to the plane of the array;
a plurality of optical elements each comprising a first surface that is textured and extending in a first direction, an oppositely positioned second surface that is planar, and side surfaces perpendicular to and connecting the first surface and second surface and extending in a second direction perpendicular to the first direction, the side surfaces being planar, each optical element having its second surface attached to the first surface of a corresponding phosphor pixel, its side surfaces aligned with corresponding ones of the side surfaces of the phosphor pixel and corresponding ones of the side surfaces of the semiconductor light emitting diode structure to collectively form a planar surface, and a thickness of about 5 microns to about 50 microns perpendicular to the first surface of the phosphor pixel, and
a reflective or scattering material disposed between and directly contacting adjacent ones of the semiconductor light emitting diode structures, adjacent ones of the phosphor pixels, and adjacent ones of the optical elements.
2. The light emitting device of claim 1 , wherein the second surface of each optical element is patterned to form a lens.
3. The light emitting device of claim 1 , wherein the second surface of each optical element is patterned to form a Fresnel lens.
4. The light emitting device of claim 1 , wherein the second surface of each optical element is patterned to enhance light extraction from the phosphor pixel.
5. The light emitting device of claim 1 , wherein the second surface of each optical element is patterned to scatter light so it appears white under white light illumination when the corresponding semiconductor light emitting diode structure is not operating.
6. The light emitting device of claim 1 , wherein each optical element is formed from a transparent or colored glass.
7. The light emitting device of claim 1 , further comprising TiO 2 particles embedded in silicone disposed between adjacent phosphor pixels.
8. The light emitting device of claim 1 , wherein each optical element is formed from a material that is translucent under white light illumination.
9. The light emitting device of claim 1 , wherein each optical element is formed from a crystalline material.
10. The light emitting device of claim 1 , wherein each optical element is a dichroic filter.
11. The light emitting device of claim 1 , wherein each optical element is permeable to oxygen.
12. The light emitting device of claim 1 , wherein each optical element polarizes light or rotates the polarization of light.
13. The light emitting device of claim 1 , comprising one or more air pockets between each optical element and the phosphor pixel to which it is attached.
14. The light emitting device of claim 1 , wherein each optical element is formed from a transparent glass.
15. The light emitting device of claim 1 , wherein each optical element is formed from a colored glass.