Linker Engineering of Dimerized Small Molecule Acceptors for Highly Efficient and Stable Organic Solar Cells

High power conversion efficiency (PCE) and long-term stability are important requirements for commercialization of organic solar cells (OSCs). In this study, we demonstrate efficient (PCE = 18.60%) and stable (t80% lifetime > 4000 h) OSCs by developing a series of dimerized small-molecule acceptors (DSMAs). We prepared three different DSMAs (DYT, DYV, and DYTVT) by using different linkers (i.e., thiophene, vinylene, and thiophene– vinylene– thiophene), to connect their two Y-based building blocks. We find that the crystalline properties and glass transition temperature (Tg) of DSMAs can be systematically modulated by the linker selection. A DYV-based OSC achieves the highest PCE (18.60%) among the DSMA-based OSCs owing to the appropriate backbone rigidity of DYV, leading to an optimal blend morphology and high electron mobility. Importantly, the DYV-based OSC also demonstrates excellent operational stability under 1-sun illumination, i.e., a t80% lifetime of 4005 h.