Volatile Coordination-Driven Surface Reconstruction for Stable Tin Perovskite Transistors

Lead-free tin (Sn²⁺) halide perovskites offer tunable bandgaps and favorable charge transport, making them attractive candidates for next-generation optoelectronic and electronic devices. Their practical deployment, however, is constrained by a redox instability intrinsic to undercoordinated Sn²⁺ sites at the surface: this instability triggers uncontrolled self-p-doping and accelerates oxidative degradation. We address this limitation through a volatile coordination strategy, in which transient acetate species coordinate to the perovskite surface and subsequently volatilize, driving a reconstruction that converts reactive SnI₂-terminated surfaces into chemically equilibrated, defect-mitigated interfaces. As a result, undercoordinated Sn-related trap states are suppressed and local stoichiometry is stabilized. Transistors built on these reconstructed surfaces exhibit robust p-type transport, a near-zero threshold voltage, and on/off ratios above 10⁸. The reconstructed interface also functions as a self-passivating, thermally resilient barrier: devices retain stable operation for over one month at 100 °C, reflecting a substantial gain in environmental durability. Notably, the devices also exhibit markedly enhanced ambient stability, along with a reversible response to air exposure. Collectively, these results identify volatile coordination-driven surface reconstruction as a general strategy for defect equilibration in metastable semiconductors, opening a path toward durable, device-grade Sn²⁺-based electronics.