Dual-Functional Halide-Based Double Perovskite for Memristive and Temperature-Responsive Optical Encryption

Lead-free double perovskite (Cs2CuSbX6, X = Br, I) was systematically investigated as a multifunctional stimulus-responsive material for electronic memory and physical encryption applications. Structural and spectroscopic analyses confirmed the presence of phase-pure Cs2CuSbX6 with halide-dependent electronic structures. Memristor devices using Cs2CuSbBr6 and Cs2CuSbI6 exhibited reliable bipolar resistive switching, governed by electrochemical metallization, with distinct switching characteristics depending on halide composition. While Cs2CuSbI6 enabled low-voltage and analog conductance modulation, Cs2CuSbBr6 demonstrated superior switching uniformity and energy-efficient synaptic behavior. Beyond electrically driven operations, Cs2CuSbBr6 precursor inks enabled reversible, temperature-gated information encryption. Written patterns were concealed on paper substrates at low temperatures and revealed upon heating. X-ray diffraction analyses confirmed that visibility changes originated from reversible physical modulation rather than irreversible chemical transformation. These results highlight Cs2CuSbBr6 as a versatile, stimulus-responsive material combining memristive electronics and physical security platforms.