Influence of Thickness of Remote Phosphor Layer on the Phosphor Temperature for High Power White LEDs

摘要

Thermal management is of critical importance for high power light-emitting diodes (LEDs). More than 60% of the electrical power input is converted into heat and built up at the junctions of LED chips due to non-radiative recombination of electron-hole pairs and low light extraction. In phosphor based white LED emitters, the involvement of phosphors in the light extraction process not only reduces the optical efficiency but also deteriorates the thermal performance. The blue light emitted from the chip is partially absorbed, partially converted to yellow light, and partially scattered upon impinging on the phosphors. Therefore, heat is generated in phosphor materials due to non-unity wavelength conversion efficiency, Stokes shift loss, and self-absorption of yellow light by the phosphors. It is well established that the juncture temperature determines the lumen performance and the device life time for LED emitters. Interests are currently being aroused among researchers in the thermal performance of the phosphors, which determines the efficiency of the emitters. In this study, the influence of the thickness of remote phosphor layer on the phosphor temperature for high power white LEDs was investigated by considering the optical-thermal energy conversion process in real emitters.