Sulfur‐Containing Perylene Diimide Derivative as Electron Transport Layer in Organic Photovoltaics

Abstract While perylene diimide derivatives such as PDINN and PDINO have demonstrated excellent efficiency as electron transport layers (ETLs) in organic photovoltaic (OPV) devices, the parent compound PDIN exhibits limited solubility in methanol due to its extended conjugated aromatic structure, restricting its practical application. Herein, a sulfur‐containing ETL, PDIN‐SO, synthesized via a facile one‐step process is reported by introducing sulfur dioxide (SO ₂ ) gas to PDIN. This straightforward synthetic approach yields a compound with exceptional methanol solubility, addressing a key limitation of conventional materials. OPV devices with PDIN‐SO as the ETL demonstrated performance comparable to those utilizing established ETL materials, including PFN‐Br and PDINO. Notably, PDIN‐SO‐based devices exhibited remarkable tolerance to variations in sulfur content, indicating robust processing versatility. When implemented with a PM6: BTP‐eC9: L8‐BO active layer, optimized devices achieved an impressive power conversion efficiency (PCE) of 18%. This work demonstrates that PDIN‐SO, with its simplified synthesis pathway, excellent solubility, and outstanding device performance, represents a promising ETL material that can accelerate the development of high‐efficiency, stable OPVs.