Rare‐Earth‐Ion Doped Bi1.5ZnNb1.5O7 Photochromics: A Fast Self‐Recoverable Optical Storage Medium for Dynamic Anti‐Counterfeiting with High Security

Abstract Conventional inorganic photochromic (PC) anti‐counterfeiting material generally require time‐consuming identification of information or response to changes in display information, resulting in low‐level readout and decoding efficiency. In this study, a new type of inorganic PC self‐bleaching material, i.e., rare‐earth‐ion‐doped Bi 1.5 ZnNb 1.5 O 7 (BZN) ceramic and corresponding mono‐/bi‐crystalline‐phase glass ceramic (GC) composite, are developed. The as‐prepared materials reveal maximum self‐recovery levels of the PC and the PC modulated upconversion luminescence ≈96.61% and 99.55%, respectively, and the self‐bleaching times are less than 20 min to the naked eyes. Unlike conventional thoughts of electrons’ trapping/detrapping with the aid of conduction band/valence band transportation, a new PC mechanism for ferroelectric oxides, involving the state exchanges between defects and color centers via direct electron transfer, is proposed. The proof‐of‐concept experiments demonstrate the unparalleled potentials offered by the self‐driven‐recovery BZN‐based bi‐crystalline‐phase GC composite for encoding, displaying, and erasing of time‐dependent information. The brought dynamical anti‐counterfeiting based on multimode optical storage favors to achieve complexity and concealment of the encrypted information to meet high‐security standard. This finding offers unique insight for designing integrated stimuli‐responsive and time‐dependent smart devices, particularly advanced anti‐counterfeiting technology.