A glass phosphor layer with ultra-high thermal stability appropriate for phosphor-converted white light-emitting diodes (PC-WLEDs) is demonstrated. The results showed PC-WLEDs utilizing the high thermal stable glass phosphor maintained good thermal stability in lumen, chromaticity, and transmittance characteristics under the thermal aging condition up to 350 °C. This is a considerable high operating temperature for a phosphor layer in the PC-WLEDs. The lumen degradation, chromaticity shift, and transmittance loss in the glass-based PC-WLEDs under thermal aging at 150 °C, 250 °C, 350 °C, and 450 °C are also presented and compared with those of silicone-based PC-WLEDs under thermal aging at 150 °Cand 250 °C. The result clearly demonstrated that the glass-based PC-WLEDs exhibited better thermal stability in lumen degradation, chromaticity shift, and transmittance loss than the silicone-based PC-WLEDs. The advantages of glass encapsulation in high-temperature operation of the PC-WLEDs could be explained that the glass transition temperature of the glass phosphor (567 °C) was much higher than it of silicone (150 °C). The newly developed ultra-high thermal-stable glass is essentially critical to the application of LED modules in the area where the high-power, high-temperature and absolute reliability are required for use in the next-generation solid-state lighting.
© 2013 IEEE
Chun-Chin Tsai, Wei-Chih Cheng, Jin-Kai Chang, Li-Yin Chen, Ji-Hung Chen, Yi-Cheng Hsu, and Wood-Hi Cheng, "Ultra-High Thermal-Stable Glass Phosphor Layer for Phosphor-Converted White Light-Emitting Diodes," J. Display Technol. 9, 427-432 (2013)