Zn Substitution-Induced Trapping-State Engineering in Gallate Phosphors for Optical Information Storage and Encryption

Long afterglow phosphors have attracted considerable attention in information encryption and storage fields due to their persistent emission characteristics under dark conditions. Generally, the afterglow properties are closely connected to the trapping states induced by atomic defects in phosphors. Although numerous phosphors with various atomic defects have been synthesized for optical applications, accurately tuning the atomic defects and trapping states in phosphors to achieve a desirable afterglow emission is a significant challenge. Herein, we report a series of gallate phosphors with tunable luminescence and afterglow emission via Zn-substitution strategies. In this SrGa2O4:Cu2+, Zn2+ phosphor system, the introduction of Zn leads to lattice distortion and modulated position/concentration of traps due to the generation of oxygen vacancies. Experimental and theoretical results demonstrate that increasing the Zn-substitution concentration can enhance the oxygen vacancy concentration in the obtained gallate phosphors, thereby delivering a prolonged afterglow time and increased intensity. Moreover, the concentration of deep traps increases with more oxygen defects in the phosphors, which can endow modulated afterglow properties under different thermal conditions. On account of the luminous behavior, the dual-channel information encryption and storage scheme is designed, providing new opportunities to exploit phosphors for advanced information storage and encryption.