Colloidal Synthesis of Sub‐1‐nm PbSe Nanowires via Cation Exchange for High‐Performance Near‐Infrared Self‐Powered Photoelectrochemical‐Type Photodetectors

Sub-1-nm nanowires (NWs) with fascinating physicochemical properties have demonstrated remarkable potential for applications across various fields. However, it remains a great challenge to prepare sub-1-nm NWs with near-infrared (NIR) absorption characteristics and explore their optoelectronic applications, so far. Herein, a novel cation-exchange strategy in N, N-dimethylformamide (DMF) solvent is introduced to synthesize sub-1-nm PbSe NWs, starting from sub-1-nm ZnSe NWs. Theoretical calculations and nuclear magnetic resonance (NMR) measurements have confirmed that the cation exchange reaction in DMF effectively reduces the barriers for Zn²⁺ extraction and Pb²⁺ introduction compared to the conventional toluene/methanol system. Notably, the resulting sub-1-nm PbSe NWs exhibit a strong absorption peak at ≈940 nm. Leveraging their unique NIR absorption features and superior carrier transport properties, self-powered photoelectrochemical-type (PEC) photodetectors is fabricated based on sub-1-nm PbSe NWs embedded in polyvinylidene fluoride (PVDF) composite films. These photodetectors demonstrated exceptional photoresponse performance under 940 nm illumination (8.0 mW cm^-2), with a typical on/off ratio of 4860, a detectivity of 4.65 × 10¹¹ Jones, and a responsivity of 113 mA W^-1. This work provides a new approach for developing and investigating NIR photoactive sub-1-nm semiconductor NWs with broad application prospects.