Synergistic chromatic switching in Cs₂NaYCl₆ perovskites composites for dynamic anti-counterfeiting

Traditional optical encryption technologies continue to encounter limitations in information security and transmission, presenting significant challenges for the development of advanced platforms in multidimensional encryption and complex information processing. Herein, by precisely modulating Ho³⁺ doping concentrations in Cs₂NaYCl₆ perovskite crystals (PCs), the single-ion-activated full-color dynamic responsiveness is achieved via the interplay between multiphonon relaxation and cross-relaxation processes. The introduction of Sb³⁺ ions induces self-trapped states that establish an effective energy transfer pathway, enhancing photoluminescence and chromaticity discrimination. Furthermore, the PCs are embedded into polyacrylonitrile (PAN) matrix to enhance crystalline stability, improve mechanical flexibility, and expand anti-counterfeiting applications. Leveraging the dual advantages of chromatic switching from PCs and fibrillar remodeling, a layered encryption platform with dynamic information display functionality is developed. This study demonstrates programmable and stimulus-responsive optical behavior under external fields, enhancing the information carrying capacity and decoding complexity, thereby offering an innovative solution for contemporary information protection.