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

ABSTRACT This work reports the resistive switching performance and physical modeling analysis of hysteresis in lead‐free all‐inorganic mixed halide perovskite memristors. Ag/Cs ₃ Bi ₂ I ₉ ₋ _x Br _x /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 10 ¹ , 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.