Trap-Engineered Deep Ultraviolet and NIR Persistent Bi-Activated Phosphor: Luminescence Tailoring via Secondary Cation Substitution in the Garnet Framework

Deep ultraviolet-B (UVB)-emitting persistent luminescent materials have aroused great interest for applications in optical information storage in ambient light, anticounterfeiting, medical diagnosis, and sterilization. However, such materials are relatively scarce. Designing non-rare-earth, Bi-doped phosphors with trap-controlled luminescence presents a promising approach to developing efficient UVB persistent luminescent phosphors. Herein, we developed a Ca 3 Ga 2 Ge 3 O 12:Bi garnet phosphor that exhibits long-lasting UVB and near-infrared (NIR) persistent luminescence (PersL) due to the copresence of Bi 3+ and Bi 2+ and the visible emission of Bi pairs. Density functional theory calculations and experimental analysis, including thermoluminescence and positron annihilation lifetime spectroscopy, revealed the stabilization of intrinsic ( V O, V Ga ‴ ) and generated defects ( V Ca ″, Bi Ca • ) by aliovalent substitution, leading to prolonged afterglow and energy storage. Ca 3 Ga 2 Ge 3 O 12:Bi demonstrates excellent antibacterial efficiency owing to long UVB PersL and thus can be used for pathogen-free surfaces and long-term self-sterilizing materials. Furthermore, trap engineering through the introduction of secondary cations (Al 3+, Sc 3+, Sr 2+, Mg 2+, and Zn 2+ ) allows precise modulation of shallow to deep trap depths and tunable UVB/NIR luminescence of Bi 3+/2+ ions. Notably, Mg 2+ and Zn 2+ doping reduced shallow traps and favored deeper trap formation, enhancing the phosphor’s suitability for photostimulated luminescence applications. This study provides insights into trap-controlled luminescence in Bi-activated phosphors by composition modulation, offering potential applications in sterilization and optical information storage technologies.