Design of a novel bismuth-activated yellow-emitting phosphor CaBaTa2O7:Bi3+ with outstanding quantum efficiency and robust thermal stability for WLEDs

The development of highly efficient and thermally stable Bi 3+ -activated phosphors has emerged as a central focus in current research on phosphor materials. Based on the Bi 3+ -based metal-to-metal charge transfer (MMCT) transition and the characteristic of possessing a rigid crystal structure, this study successfully designed a yellow-emitting phosphor, designated as CaBaTa 2 O 7 :Bi 3+ , which exhibits high quantum efficiency and excellent thermal stability. The crystal structure, electronic structure, and luminescent properties of CaBaTa 2 O 7 :Bi 3+ were systematically investigated. Upon near-ultraviolet excitation, CaBaTa 2 O 7 :Bi 3+ emits bright yellow light centered at 552 nm, with a quantum efficiency of 96 % and thermal stability of 81 %@150 °C. The luminescence mechanism of CaBaTa 2 O 7 :Bi 3+ was explored through structural analysis, spectral characterization, and theoretical calculations, confirming that the luminescence originates from the Bi–Ta MMCT transition. Furthermore, the practical applicability of CaBaTa 2 O 7 :Bi 3+ was evaluated via WLED device packaging and hydrolysis tests. The results demonstrate that CaBaTa 2 O 7 :Bi 3+ holds significant promise for application in WLED technology.