Degree of Crystal Structure Distortion-Induced Tunable LiGaO2 Long Persistent Luminescence for Optical Information Encryption

Abstract

Tunable long persistent luminescence (LPL) phosphor materials have great potential for optoelectronic cryptographic applications. However, the mainstream techniques of modulating LPL generally have the characteristics of complex preparation processes, demanding crystal field environments, or expensive dopant ions, which restrict large-scale commercial application. Herein, we develop a simple, high-efficiency, and low-cost strategy to optimize the LPL of LiGaO₂(LGO):Cu²⁺ by changing the sintering time to regulate the degree of crystal structure distortion. The Cu²⁺ as charge compensation will substantially enhance the emission intensity of LGO by a factor of 11.02 originating from the appropriate ionic size and coordination mode. Besides, the LPL time of LGO:Cu²⁺ can be extended effectively to 2 h by adjusting the sintering temperature and time (900 °C@24 h). The extension mechanism is that Li and Ga can be substituted for each other more easily and induce crystal structure distortion due to the special crystal structure of LGO, resulting in an optimal trap concentration in LGO:Cu²⁺. Thus, our findings provide a simple way to modulate long persistent luminescence and further consider their potential impact on optical information encryption.