Reductive contact and dipolar interface engineering enable stable flexible CsSnI₃ nanowire photodetectors

Lead-free tin-based halide perovskites are attractive for flexible and environmentally benign optoelectronics, but their application is limited by the rapid oxidation of Sn²⁺ to Sn⁴⁺ and poor operational stability. Here, we report a flexible CsSnI₃ nanowire photodetector that achieves both high near-infrared photoresponse and long-term stability through synergistic aluminium-substrate contact engineering and dipolar interface modification. A 0.2 mm anodized aluminium foil serves as the flexible substrate, where localized laser ablation exposes metallic aluminium regions that act as reductive sites, effectively suppressing Sn²⁺ oxidation during nanowire growth. Simultaneously, a polar interlayer of 3-fluoro-2-nitroanisole (3F-2NA) is introduced to improve energy-level alignment, suppress interfacial deprotonation, and enhance charge extraction. The resulting device exhibits a responsivity of 0.39 A W^-1, a specific detectivity of 1.38 × 10¹³ Jones, and a wide linear dynamic range of 156 dB under 850 nm illumination. Moreover, the device retains over 85% of its initial photocurrent after 60 days under ambient laboratory conditions and maintains 94% after 1000 bending cycles. This work establishes an effective strategy for stabilizing Sn-based perovskites toward high-performance flexible optoelectronic devices.