3-Methylthiophene: A Sustainable Solvent for High-Performance Organic Solar Cells

The use of harmful halogenated or aromatic solvents such as chloroform (CF), chlorobenzene (CB), and <i>o</i>-xylene (<i>o</i>-XY) is one of the greatest barriers to the industrial-scale manufacturing of high-performance organic solar cells (OSCs). Therefore, it is necessary to eliminate the effects of these solvents to ensure practical feasibility of OSCs. We found that the anthracene-terminated polymer donor and small-molecule acceptor BO-4Cl had good solubility in 3-methylthiophene (3-MeT). There were no toxicity labels in the SDS and exposure control limits for 3-MeT. An overall power conversion efficiency of 16.87% was achieved by using 3-MeT as the solvent for solar cell fabrication, which was higher than that of the cells made from CF (16.18%) and <i>o</i>-XY (15.69%). The best OSC based on PM6:D18:L8-BO and fabricated with 3-MeT exhibited a high PCE of 18.13%, which is one of the highest values for cells fabricated from halogen-free solvents. These results indicate that 3-MeT is an eco-friendly and low-toxicity solvent for the sustainable fabrication of the OSC active layer.