Lead-Free Bismuth Halide Perovskite Memristors: Low-Voltage Switching and Physical Modeling of Resistive Hysteresis

[EN] This work reports the resistive switching performance and physical modeling analysis of hysteresis in lead-free all-inorganic mixed halide perovskite memristors. Ag/Cs3Bi2I9(-)xBrx/ITO memristors with I-rich (x = 3) and Br-rich (x = 6) crystallize in a layered trigonal phase and form smooth and uniform films confirmed by XRD, SEM, and AFM analyses. Both devices exhibit reproducible bipolar switching with below 0.3 V SET/RESET voltages, ON/OFF ratios above 101, and excellent cycling and retention stability. Crucially, this study provides the first direct experimental validation of the conductance-activated quasi-linear memristor (CALM) framework in bismuth-based halide PSK memristors, showing quantitative agreement between measured and simulated I-V hysteresis. Electrical analysis combined with scan-rate-dependent I-V physical modeling reveals ion-migration-controlled filament dynamics. I-rich layers form uniform and stable filaments due to stronger Bi-I bonding and lower density of mobile halide vacancies, produced uniform and stable conductive filaments. In contrast, Br-rich memristors exhibit ultralow voltage operations enabled by enhanced vacancy mobility, albeit with slightly broader switching thresholds. These findings demonstrate that compositional engineering in Pb-free bismuth PSK enables a balance between low-voltage operation and stable switching by the incorporation of Br- ions. The combined experimental-modeling approach establishes a robust lead-free materials platform for next-generation energy-efficient non-volatile memory and neuromorphic electronics.