Voltage-Programmable Switching in Halide Perovskite Memristors by Asymmetric Contact Engineering

Metal halide perovskites combine mixed ionic-electronic conduction with low-temperature processing, yet most perovskite memristors operate in a single mode, either nonvolatile bipolar resistive switching (RS) or volatile threshold switching (TS). This limits in-device multi-role reuse and drives peripheral overhead. We introduce a single asymmetric transport layer at one contact that makes bias polarity the mode selector. The built-in field adds to or opposes the applied field, yielding nonvolatile RS under positive sweeps and volatile TS with self-reset under negative sweeps in the same device. The approach is process-compatible across C₆₀, NiO_x, and Spiro-OMeTAD. In C₆₀-based devices, we further observe improved retention (∼2.0 × 10⁴ s), endurance (∼6 × 10³ cycles), and storage stability (∼1300 h) vs. symmetric control. Mechanistically, Mott-Schottky analysis reveals a finite built-in voltage that stabilizes or dissolves halide-vacancy filaments depending on polarity, explaining the reconfigurability. Functionally, negative pulses realize short-term, self-erasing updates, while positive pulses consolidate long-term weights under a unified read bias-providing an intrinsic stability-plasticity balance. This minimal asymmetry streamlines compute-in-memory and neuromorphic systems.