Self-Passivating Perovskite-Electrode Interfaces Enabled by Field-Induced Phase Transformation

Halide perovskites are promising semiconductors for optoelectronic and radiation-detection applications, yet their operational stability is often constrained by dynamically uncontrolled electrode/perovskite interfaces under electrical bias. Here, we report a self-passivating perovskite-electrode interface enabled by field-induced phase transformation. Unlike conventional molecular passivation or buffer-layer engineering, this strategy exploits chemical potential differences among the metal electrode, halide species, and ambient environment to redirect bias-driven interfacial reactions into adaptive stabilization. Using Bi/FAPbBr₃ as a model system, we show electrical bias drives a controllable in situ electrochemical transformation that converts the contact into dense, and self-limiting BiOBr interlayer while preserving the perovskite bulk. This metal oxyhalide layer provides robust interfacial bonding, favorable energy-level alignment, and ultradense nanometer-scale barrier against further ionic accumulation and degradation. As a stringent demonstration under kilovolt-level bias, γ-ray detectors based on this adaptive junction tolerate up to 1000 V and achieve an energy resolution of 3.6 keV at 122 keV, among the best values reported for perovskite γ-ray detectors. This work establishes field-induced interfacial phase transformation as a general strategy for stabilizing perovskite contacts under realistic operating conditions.