Polarity‐Controlled Coexistence of Electrochemical Metallization and Valence Change Mechanisms in a Unified Metal Halide Perovskite Memristor

ABSTRACT Metal halide perovskites (MHPs), owing to their mixed ionic‐electronic conductivity and defect‐tolerant lattice, have emerged as promising candidates for next‐generation memristors. Yet, the interplay of distinct resistive switching mechanisms remains poorly understood. Here, we provide direct experimental evidence that two distinct resistive switching mechanisms, electrochemical metallization (ECM), driven by the reactive metal electrode, and the valence change mechanism (VCM), mediated by intrinsic ion migration within the perovskite lattice, can coexist within the same perovskite memristor and can be selectively activated by simply reversing the electroforming voltage polarity, without altering the device structure or active layer composition. This controllable switching enables a systematic comparison of their intrinsic performance. ECM‐driven devices exhibit low operating voltages (+0.18/−0.3 V), high endurance (> 10 4 cycles), and moderate retention (∼ 4 × 10 3 s), whereas VCM switching achieves superior data retention (∼ 7 × 10 3 s) and a higher resistance contrast (∼ 10 5 ), albeit with higher operating voltages and reduced cycling stability. Replacing the active Ag electrode with inert contacts confirms the absence of ECM and isolates intrinsic ion migration as the origin of VCM switching. These findings establish a clear framework for distinguishing and engineering operating mechanisms in MHP‐based memristors, providing design guidelines for reliable, multifunctional memory and neuromorphic devices.