Effects of YAG: Ce Phosphor Particle Size on Luminous Flux and Angular Color Uniformity of Phosphor-Converted White LEDs

Effects of YAG:Ce phosphor particle size on the luminous flux and angular color uniformity have been studied by using Monte Carlo ray-tracing simulation. A white LED model basing on Cree XLamp is constructed. The phosphor particle size is changed from 2 to 20 mu m. Different simulation cases are carried out by changing the phosphor concentration and thickness. Results revealed that the luminous flux and angular color uniformity have complex relationships with the particle size depending on applied phosphor concentration and desired color temperature. A general finding is that an increase of the particle size is beneficial for the improvement of luminous flux but leads to worse angular color uniformity. A 2 mu m particle achieves not only the best angular color uniformity but the lowest luminous flux. A particle size larger than 10 mu m generates the highest luminous flux at low color temperature when the concentration is around 1.5 g/cm. A particle size between 2 mu m and 10 mu m shows combined moderate performance when the phosphor concentration is higher than 2 g/cm(3). To realize the best combined performance, a particle size around 6 mu m is suggested.