Moderate Trap Engineering for Enhanced Thermal Stability and High Efficiency in a Bi³⁺-Doped Phosphor

Trap engineering is widely applied to contend with thermal quenching of phosphors. However, the incidental detriment of the luminescent efficiency has long been neglected. Herein, we propose a paradigm for achieving a high-performing Bi3+-doped phosphor with moderate trap engineering. Through introducing appropriate traps in a neutral atmosphere and proper doping concentration, we have successfully created a novel Ba2GdAlO5:Bi3+ yellow phosphor that exhibits exceptional thermal stability (104.1%@423 K) and a high internal quantum yield (82.78%), which is the top performance among Bi3+-doped phosphors. The oxygen vacancy and Bi2+ were identified as the responsible traps through X-ray photoelectron spectroscopy, while their depth was measured to be 0.9 eV by using thermoluminescence. Notably, the phosphor exhibited photochromism upon near-ultraviolet (n-UV) excitation and could be bleached through heat treatment. These observations highlight its potential for various applications. Finally, two white lighting devices with a color rendering index exceeding 90 were prepared with n-UV LED chips by applying Ba2GdAlO5:Bi3+ as one of the phosphors. This study not only provides a high-performance Bi3+-doped phosphor suitable for high-quality white LED (WLED) lighting but also proposes a methodology for designing phosphors with high efficiency and thermal stability..