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

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 Bi1.5ZnNb1.5O7 (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 approximate to 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.