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

Abstract 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 Zn ²⁺ extraction and Pb ²⁺ 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 × 10 ¹¹ 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.