Highly Luminescent Zero-Dimensional (Ph ₃ S) ₂ HfCl ₆ : Sb ³⁺ Hybrid Crystal Exhibiting Dual-Mode Afterglow for Information Encryption

Room-temperature phosphorescent materials have garnered significant attention in the realm of encryption and information encoding due to their unique capability of sustained emitting after the excitation source is removed. However, conventional single-mode encryption techniques often suffer from insufficient security, highlighting the imperative need to develop more robust, multimode encryption agents. In this study, a zero-dimensional organic-inorganic hybrid metal halide crystal, (Ph₃S)₂HfCl₆ ([Ph₃S]: triphenyl sulfonium), was successfully synthesized and explored for time-resolved information encryption applications. Through the strategic incorporation of Sb³⁺ ions into (Ph₃S)₂HfCl₆, an efficient energy transfer pathway was established from the singlet S₁ and triplet T_n state, enabling self-trapped excitons (STEs). This doping process significantly enhanced the crystal's photoluminescence quantum yield from 33.5% to a remarkable 71.26%. Furthermore, the (Ph₃S)₂HfCl₆: x%Sb³⁺ composite exhibited a fascinating combination of afterglow and STE emissions, each with distinct decay characteristics and durations. This unique two-level lifetime property facilitates encryption with higher security, which has been successfully demonstrated for ASCII binary and decimal encoding applications. These findings underscore the substantial potential of (Ph₃S)₂HfCl₆: x%Sb³⁺ as a sustainable encryption agent, which is capable of facilitating one-time encoding and twice-decoding processes.