Kinetics‐Tunable Photochromism and Dual‐Mode Luminescence Modulation in BaTiO₃‐Based Phosphors for Dynamic Anti‐Counterfeiting Application

Abstract

The security level of traditional optical anti‐counterfeiting agents is increasingly insufficient to meet the demands of a rapidly advancing society, resulting in significant losses for individuals and corporations. In this study, a series of pure and lanthanides‐doped BaTiO3 （BTO） phosphors are synthesized, exhibiting reversible photochromic and bleaching phenomenon through alternating UV light irradiation and thermal treatment. The maximum coloration contrast of the samples is influenced by the choice of dopants, primarily due to the variation in oxygen vacancy concentrations. Notably, lanthanide doping accelerates the photochromic response compared to the undoped sample, attributed to enhanced carrier mobility and concentration from the introduction of intermediate energy levels. Multi‐mode upconversion luminescence modulation (UCL) is achieved through the re‐absorption effect, yielding maximum green (λex = 980 nm) and red (λex = 1550 nm) UCL modulation rate of 67% and 59%, respectively. Furthermore, an application in temporal encryption is demonstrated, leveraging the kinetics‐tunable photochromism and multi‐mode UCL of BaTiO3‐based phosphors.