High‐Performance All‐Small‐Molecule Organic Solar Cells With Nonfused Ring Acceptors Enabled by Halogen‐Free Processing

Small‐molecule organic photovoltaic materials offer advantages of precise molecular definition, high purity, and excellent reproducibility, making them promising for large‐scale applications. However, almost all‐small‐molecule organic solar cells (ASM‐OSCs) rely on fused‐ring electron acceptors and halogenated solvents, whose complex synthesis, high cost, and environmental hazards hinder commercialization. To address these challenges, we report halogen‐free ASM‐OSCs based on nonfused‐ring acceptors (NFREAs). Using the nonfused acceptor 2BTh‐2F and donor MPhS‐C6, we systematically investigated various halogen‐free processing solvents. The blend film processed with high‐boiling‐point toluene exhibited optimal nanoscale morphology, with balanced molecular self‐assembly and well‐defined nanofibrillar domains that promoted efficient charge transport. As a result, the corresponding device achieved a power conversion efficiency of 13.89%, substantially exceeding the 11.58% achieved with chloroform and representing the highest device performance reported for halogen‐free ASM‐OSCs employing NFREAs. This work provides a practical and environmentally friendly strategy toward scalable, high‐performance, halogen‐free OSCs.