Reductive Contact and Dipolar Interface Engineering Enable Stable Flexible CsSnI3 Nanowire Photodetectors

Abstract

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 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 * 10^13 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 in ambient air and maintains 94% of its initial photocurrent after 1000 bending cycles. This work establishes an effective strategy for stabilizing Sn-based perovskites toward high-performance flexible optoelectronic devices.