Dual‐Stimuli Reversible Photochromism and Persistent Luminescence in Eu ³⁺ ‐Doped Sr ₂ YTaO ₆ for Multimode Optical Encryption

The increasing sophistication of counterfeiting has created an urgent demand for advanced optical materials with dynamic, multidimensional, and difficult‐to‐replicate responses for high‐security information protection. Although multi‐stimuli‐responsive luminescent materials have attracted considerable attention, many still suffer from single excitation modes or limited reversibility, restricting their practical use in advanced anti‐counterfeiting. Herein, we report a Eu 3+ ‐doped Sr 2 YTaO 6 material that integrates reversible photochromism (PC), photoluminescence (PL), and persistent luminescence (PersL) within a single material. Under both UV light and X‐ray irradiation, the material exhibits pronounced reversible PC, and the coloration degree can be precisely regulated by the Eu 3+ doping concentration, enabling grayscale optical encryption. In addition, the material shows characteristic red emission under multiple excitation modes together with red PersL. Thermoluminescence (TL) demonstrates that the PC and PersL behaviors originate from a synergistic trap system consisting of shallow, medium, and deep traps, which govern carrier trapping, storage, and release. Benefiting from these properties, a practical screen‐printing strategy was developed to fabricate complex stimulus‐responsive encrypted patterns, and a concentration‐gradient‐based encoding/decoding system was constructed. The Sr 2 YTaO 6 :Eu 3+ material provides a versatile platform for integrating reversible photochromic performance, tunable luminescence, and PersL, and offers a scalable route toward high‐security optical encryption for product authentication and document protection.