HI‐Mediated In Situ Nitro Reduction and Film Optimization Enable High‐Performance Water‐Stable Quasi‐1D Perovskite Photodetectors

Hybrid organic-inorganic perovskites show great promise for optoelectronics but suffer from moisture-induced degradation. Here, we report (4NBPZ)Pb₂I₆ (NBPI), a novel quasi-1D perovskite achieving exceptional water stability through cation-π interactions and outstanding photodetector performance via processing optimization. During synthesis, 4-nitrobenzylpyridine undergoes unprecedented in situ HI-mediated reduction to 4-aminobenzylpyridinium (4NBPZ). The crystal structure features long-range cation-π interactions (3.98 Å spacing) that effectively shield the inorganic framework from water-induced degradation, enabling structural and optical stability exceeding 100 days of continuous water exposure. While initial photodetector performance was limited by poor film morphology, systematic hydroiodic acid treatment dramatically enhanced device metrics by dissolving colloidal clusters and improving film uniformity. The optimized photodetector achieved remarkable performance: responsivity of 3.02 A/W, external quantum efficiency of 1020%, and detectivity of 2.36 × 10¹¹ Jones, representing three orders of magnitude improvement over pristine NBPI devices. This work demonstrates that combining intrinsic stability mechanisms with strategic performance enhancement provides a comprehensive solution to the dual challenges facing perovskite optoelectronics, opening pathways for practical water-stable, high-performance devices.