Thermal influence of phosphor to GaN-based white LEDs

In this study, we quantitatively investigate the influence of phosphor to the thermal properties of white LEDs. We find that although the junction temperature of white LEDs is higher than corresponding blue LEDs, due to the high thermal conductivity of the phosphor, it will help to improve the thermal dissipation and lower the thermal resistance of white LEDs. Based on this, a heat transfer model has been proposed, which has also been confirmed by simulation analysis. While for white LEDs with remote phosphors, although the lower junction temperature can help to improve performance and reliability, the thermal resistance has not been improved. The heat generated by phosphors is isolated by the silicone and this would increase the phosphor temperature and lead to a different degradation mechanism after a long time stress.