Kinetics-tunable photochromic platform in perovskites for advanced dynamic information encryption

Dynamically stimulated color-changing materials provide channels within a multidimensional spatial platform and hold significant potential in the field of information bearing. However, manipulating the photochromic conversion of individual lanthanide emitters and external stimuli to achieve color-switchable emission remains a challenge. Here, multiphonon relaxation between energy levels and cross-relaxation among ions have been manipulated to control the population distribution of different energy levels in Eu³⁺ ions doped ultra-low-phonon energy Cs₂NaYCl₆ (CNYC) crystals, finally achieving full-spectral color switching. Interestingly, the introduction of Tb³⁺, not only enriches the interaction of color information in the spatial dimension, but the water-stimulated phase transition, which triggers the energetic coupling between the Tb³⁺ and Eu³⁺ ions in the lattice. By controlling the water-soaking time, the reversible change in luminescence color from red-orange to yellow to green have been observed. When these materials encode information, the effectiveness of anti-counterfeiting is verified by demonstrated experiment. In this study, a breakthrough in reversible phase transition of CNYC triggered by water have been observed, and a multidimensional synergistic anti-counterfeiting platform, encompassing spacetime security − photoresponsive channel switching − stimulus remodeling, have been innovatively established. These have promoted the development and improvement of anti-counterfeiting mechanisms.