Eu3+-Tb3+-Tm3+ co-doped oxyfluoride glass with high quantum yield for a robust white LED color converter

Abstract

BaF2–Al2O3–B2O3–SiO2 glasses and glass-ceramics doped with Eu3+-Tb3+ were fabricated as an inorganic color converter for white LEDs. The BaF2–Al2O3–B2O3 glass composition was modified by adding SiO2, and thermal and mechanical stability improved with increasing SiO2 content while maintaining a quantum yield (QY) as high as 91%. To realize white color coordinates, Tm3+ was additionally introduced at varying contents, and Eu3+ content was also controlled. Excellent chromatic properties, such as a pure white color coordinates (x = 0.33, y = 0.33) with a co-related color temperature of 5772K, and a color rendering index (CRI) of 91 under 370 nm excitation, were successfully achieved. After the glass was heat-treated at 600 °C to fabricate a glass ceramic, the glass-ceramics were mounted on top of a 370 nm UV-LED, successfully demonstrating a white LED with nearly pure white color coordinates and a high CRI of 86. The increased emission intensity in the glass-ceramic was attributed to the formation of BaF2 crystals which were investigated by X-ray diffractometer (XRD) and a transmission electron microscope with energy dispersive spectroscopy (TEM-EDS).