Uniform White Emission of WLEDs Realized by Multilayer Phosphor With Pyramidal Shape and Inversed Concentration Distribution

The effect of pyramidal multilayer phosphor layout on the color uniformity of white light-emitting diodes is analyzed, using the Monte Carlo ray-tracing optical simulation. The color uniformity has been improved by tailoring the number of layers, the pyramidal shape, and the phosphor concentration distribution. Results show that Layout C, with five layers and a three step inversed concentration distribution, can realize a much more uniform white emission with an angular color variation of 55 K and an angular color uniformity of 99.17%.