Performance enhancement of white LED with TAG-Al2O3:Ce eutectic phosphor by partial Gd ion substitution

Abstract

In the traditional white LED, the phosphor is combined with the blue LED chip after mixed with the resin composite material. This combination affects the final light efficiency and color temperature, and cannot provide long-term stable work because of high emission and high temperature. Based on Tb3Al5O12-Al2O3:Ce (TAG-Al2O3:Ce) eutectic, we developed the eutectic Tb1.5Gd1.5Al5O12-Al2O3:Ce ((TG) AG-Al2O3:Ce) to overcome the shortcomings of traditional phosphors. The eutectic was grown by an optical floating zone method. X-ray diffraction shows that the structure of (TG) AG-Al2O3 do not have significant changes compared to TAG-Al2O3, and the doped Ce3+ ions do not influence the basic structure of eutectic. Scanning electron microscopy shows that these materials have typical eutectic structure of sapphire and garnet phases, which can increase the length of the optical path to reduce the reflection loss and cause a higher luminous efficiency compared to the resin phosphor. Photoluminescence emission and excitation properties of (TG) AG-Al2O3 eutectic were investigated. The main excitation is in the luminous range (450 nm to 480 nm) of the blue LED chip for white LED. Compared with TAG-Al2O3:Ce, the emission peak is slightly shifted to the red, which cause the color temperature of (TG) AG-Al2O3:Ce eutectic LED is closer to natural light. The luminous efficiency of (TG) AG-Al2O3:Ce eutectic white LED is much higher than that of TAG-Al2O3:Ce eutectic. These results show that (TG) AG-Al2O3: Ce eutectic is promising phosphor for white LEDs.