High Thermal Stability of Phosphor-Converted White Light-Emitting Diodes Employing Ce:YAG-Doped Glass

High thermal stability of phosphor-converted white light-emitting diodes (PC-WLEDs) using Ce:YAG-doped glass (CeYDG), instead of conventional Ce:YAG-doped silicone (CeYDS), as a PC layer is proposed and fabricated. The proposed CeYDG possesses host stability as glass and retains desired fluorescence as Ce:YAG. The CeYDG employed in the PC-WLED test demonstrates better performances than conventional CeYDS, including lumen loss, chromaticity shift, transmittance loss, and peak emission intensity undergoing three industry-standard reliability tests at either high (8 wt%) or low (2 wt%) doping concentrations of Ce:YAG. While the CeYDG reveals better stability than the CeYDS, we expect even better performance after refining the glass composition and fabrication process for CeYDG due to current processing facility limitations. However, this study clearly demonstrates the feasibility and advantages of adapting glass as a PC layer in PC-WLED modules that can potentially provide higher reliability and better performance for high-end LEDs, particularly in the area where strict reliability is highly required and in the environment where silicone fails to stand for long.