Improved color rendering index and thermal stability of white LEDs with phosphor-in-glass using the SiO2-B2O3-ZnO-Na2O glass system

Abstract

Phosphor in glasses (PiGs) were fabricated for color tunable white LEDs using glass of the SiO2-B2O3-ZnO-Na2O system, which can be sintered at 550 °C. CaAlSiN3:Eu2 + (CASN:Eu2 +) red phosphor was added without its thermal degradation, and a mixture with Y3Al5O12:Ce3 + (YAG:Ce3 +) yellow phosphor demonstrated color tunable white LEDs when mounted on a blue LED. Variation of the glass to phosphor and phosphor to phosphor mixing ratio achieved a highly improved color rendering index (CRI), of up to 93. Thermal quenching property was also improved, reaching 98% of its original intensity even at 200 °C; the value depended on the phosphor content. Thermal conductivity values elucidate the improvement.