Temperature-dependent trap engineering in gallate long afterglow phosphor for advanced information encryption and anti-counterfeiting

Long-persistent luminescence (LPL) materials have attracted significant attention in the fields of information encryption and anti-counterfeiting due to their unique afterglow emission under darkness. However, accurately modulating afterglow behavior as well as trap states of LPL materials is highly tricky. Herein, the temperature-dependent trap engineering in Cu 2+ -doped SrGa 2 O 4 (SGOC) phosphors for tunable afterglow emission is demonstrated. By changing the sintering temperature, the luminescence and afterglow performances of SGOC can be well tuned. A series of characterizations confirmed that increasing calcination temperature results in the formation of a higher concentration of oxygen vacancy defects in SGOC, which can bring out more traps in its band gap and move the trap position to a deeper region, so as to achieve longer and stronger afterglow performance. The theoretical calculations support the role of Cu 2+ in narrowing the bandgap and enhancing electron localization in SGOC for red luminescence and afterglow emission. By virtue of their distinct afterglow and luminescence performance, the SGOC phosphors obtained at different calcination temperatures for advanced anti-counterfeiting and time-resolved information encryption were demonstrated. The temperature-dependent trap engineering proposed in this work can inspire some new concepts in exploring LPL materials with multi-mode emission for advancing information anti-counterfeiting and encryption applications. The temperature-dependent trap engineering in Cu 2+ -doped SrGa 2 O 4 phosphors for tunable afterglow emission is demonstrated, which exhibits great prospects in information encryption and anti-counterfeiting applications.