Effect of phosphor settling on the optical performance of phosphor-converted white light-emitting diode

Phosphor settling phenomena exists during the phosphor coating process in the light emitting diode (LED) packaging industry. It is perceived that phosphor settling will affect the concentration of the phosphor, and consequently the concentration will influence the optical performance of phosphor-converted white LED light source. In this paper, an experiment based on the real packaging process was conducted to investigate the phosphor settling phenomena. It was found that the concentration variation of the phosphor embedded in the silicone matrix was very small (less than 1%). Based on the observation of the experiments, the effect of the phosphor settling in the silicone matrix on light extraction efficiency (LEE), correlated color temperature (CCT), angular color uniformity (ACU) and light intensity distribution curve (LIDC) was investigated and discussed by the three dimensional Monte Carlo ray-tracing simulations. It was discovered that the effect of the phosphor settling on the optical performance could be neglected when using the present packaging process. (C) 2011 Elsevier B.V. All rights reserved.