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 Ca₃Ga₂Ge₃O₁₂:Bi garnet phosphor that exhibits long-lasting UVB and near-infrared (NIR) persistent luminescence (PersL) due to the copresence of Bi³⁺ and Bi²⁺ 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 (VO,VGa‴) and generated defects (VCa″,BiCa•) by aliovalent substitution, leading to prolonged afterglow and energy storage. Ca₃Ga₂Ge₃O₁₂: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 (Al³⁺, Sc³⁺, Sr²⁺, Mg²⁺, and Zn²⁺) allows precise modulation of shallow to deep trap depths and tunable UVB/NIR luminescence of Bi3+/2+ ions. Notably, Mg²⁺ and Zn²⁺ 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.