Polythiophenes as electron donors in organic solar cells

Recent advancements in organic solar cells (OSCs) highlight the critical need for low-cost, readily available polymer donors to facilitate the commercialization of OSCs. Among the various photovoltaic materials, polythiophene (PT) and its derivatives have emerged as the most promising candidates for commercial applications, primarily due to their affordability and ease of scalable synthesis. Over the past few years, the combination of PTs with nonfullerene acceptors (NFAs) has led to significant improvements in photovoltaic efficiency. This paper provides a comprehensive overview of design strategies for polythiophene electron donors utilized in NFA-based OSCs, focusing on the modulation of energy levels and aggregation properties. It also evaluates recent progress in optimizing film morphology in PT:NFA blends, emphasizing key factors like donor-acceptor miscibility, solution-state aggregation control, and film-formation kinetics. Additionally, the paper explores the applications of PTs in all-polymer OSCs and large-area OSCs, as well as the stability of PT-based OSCs. Finally, the paper addresses scientific challenges associated with PT-based OSCs, aiming to provide guidance and stimulate new ideas for further research.