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

Abstract

Lead-free tin-based halide perovskites are promising candidates for flexible and environmentally benign optoelectronic devices, yet their practical deployment is severely hindered by the rapid oxidation of Sn2+ to Sn4+ and the resulting performance degradation. Here, we report a flexible cesium tin triiodide (CsSnI3) nanowire photodetector that achieves remarkable stability and high near-infrared photoresponse through aluminium (Al) substrate contact engineering and dipolar interface modification. A 0.2 mm-thick anodized Al foil serves as the flexible substrate, where localized laser ablation exposes metallic Al regions that act as reductive sites, effectively suppressing Sn2+ oxidation during crystal growth. Simultaneously, a polar interlayer of 3-fluoro-2-nitroanisole is introduced to align energy levels and mitigate interfacial deprotonation, enhancing carrier extraction and environmental robustness.The resulting CsSnI3 nanowire 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, demonstrating excellent long-term operational and mechanical stability. This work establishes a synergistic "reductive contact + dipolar modification" paradigm for suppressing Sn2+ oxidation, offering a scalable route toward high-performance, durable, and flexible lead-free perovskite optoelectronics.