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 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mo>(</mml:mo><mml:msub><mml:mi>V</mml:mi><mml:mi>O</mml:mi></mml:msub><mml:mo>,</mml:mo><mml:mspace></mml:mspace><mml:msubsup><mml:mi>V</mml:mi><mml:mi>Ga</mml:mi><mml:mrow><mml:mo>‴</mml:mo></mml:mrow></mml:msubsup><mml:mo>)</mml:mo></mml:math> and generated defects <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mo>(</mml:mo><mml:msubsup><mml:mi>V</mml:mi><mml:mi>Ca</mml:mi><mml:mo>″</mml:mo></mml:msubsup><mml:mo>,</mml:mo><mml:mspace></mml:mspace><mml:msubsup><mml:mi>Bi</mml:mi><mml:mi>Ca</mml:mi><mml:mo>•</mml:mo></mml:msubsup><mml:mo>)</mml:mo></mml:math> 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 Bi^3+/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.