Unveiling negative capacitance as a fingerprint of delayed dynamic conductance in light-modulated halide-perovskite memristors

Low-frequency negative capacitance (NC) and resistive switching (RS) are prominent dynamic phenomena in halide-perovskite memristors, yet how the slow conductance dynamics underlying RS are encoded in NC remains unclear. Here, we combine current–voltage hysteresis, impedance spectroscopy, and small-signal modeling, using illumination as a controlled perturbation to probe this relationship. Across three device structures, NC correlates with pronounced RS and state-dependent conductance modulation, while illumination can suppress or induce NC by tuning the RS-associated dynamic-conductance response. We describe these observations with a dynamic parallel-conductance model, in which a delayed conductance response introduces a negative contribution to the apparent capacitance and competes with the positive capacitive background. The results identify delayed dynamic conductance as the dynamical link between resistive-state evolution and low-frequency NC and establish NC as a frequency-domain fingerprint of the slow conductance dynamics underlying RS.