Differential Optical Responses of Robustly Single-Phased K ₃ YSi ₂ O ₇ :Ce/Tb/Gd under Diverse Stimulations toward Optical Thermometry, Dynamic Anticounterfeiting, Optical Storage, and Encryption Applications

(Co)doping luminescent center(s) in a host is a universal strategy to photoluminescence (PL) modulations for extensive applications, yet its mechanism and interactions between structure and behavior in many phosphors remain ambiguous. Herein, via a facile sol-gel reaction method, differently tendentious occupations of Ce³⁺ in distinct crystallographic sites of K₃YSi₂O₇ (KYS) lead to tunable PL in between blue and bluish-green under diverse excitations with high quantum efficiency. The generation of wide trap energy levels originating from heterovalent substitution Tb³⁺ → K⁺ could entrust Tb³⁺ as both PL and long-persistent PL (LPL) centers in green. Due to temperature-dependent filling/releasing rates of captured carriers, strong thermal-induced LPL could be obtained in KYS: Tb. By codoping Ce/Tb in KYS, multimode anticounterfeiting and information storage/encryption of KYS: Ce/Tb are realized with high security level via a screen printing technique. Because Ce and Tb possess different temperature-dependent quenching behaviors, optical temperature sensing is achieved with high absolute/relative sensitivity. To further enhance the KYS: Ce/Tb performance, trap depth engineering via equivalent substitution Gd → Y is further executed. The colorimetric/photometric analyses here provide new insights into designing novel stable and single-phased phosphor for applications in advanced anticounterfeiting technology and optical thermometry.