Benzodithiophene-Based Small-Molecule Donors for Next-Generation All-Small-Molecule Organic Photovoltaics

Organic solar cells (OSCs) have been considered being a promising candidate for next-generation photovoltaic technology because of their low carbon footprint, short energy payback time, and facile manufacture into lightweight, flexible, and semitransparent products. In this prosperous field, there is a rising trend of developing all-small-molecule (ASM) OSCs due to the distinct merits of small molecules, such as well-defined structures, facile purification, and pre-eminent batch-to-batch replicability, making it a preferential contender for industrialization. The majority of the best-performing ASM OSCs utilize benzodithiophene (BDT) donors, and recent breakthroughs demonstrate that this system has exceeded the 15% efficiency mark in the laboratory. This review analyzes the significant study that has led to this remarkable progress and focuses on the most effective BDT small-molecule donors. The pivotal structure-property relationships, donor-acceptor matching criteria, and morphology control approaches are discussed. Lastly, we summarize the remaining challenges and offer our perspective on the future advance of ASM OSCs.