Design of Dimer, Oligomer and Polymer Acceptors for 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). Small-molecule acceptors (SMAs) are the core materials that have led to remarkable advances in the PCEs of the OSCs, but the resulting OSCs typically have poor long-term stability. The low glass transition temperatures (T_gs) and rapid diffusion of SMAs owing to their small molecular sizes are recognized as the main causes of the poor stability of OSCs. In addition, the PCEs of OSCs are still lower than those of other types of photovoltaic devices, such as perovskite solar cells, mainly because of their relatively low open-circuit voltage (V_oc < 0.90 V). In this talk, we present the development of different dimer and oligomer acceptors for improving the V_ocand PCE values of the OSCs. Interestingly, dimer and oligomer acceptors have significantly higher T_gand lower diffusion coefficient compared to SMAs, which enhances the photo and thermal stabilities of the OSCs. Finally, by adding the examples of polymer acceptors, we discuss the impact of molecular sizes of acceptors in the device stabilities and mechanical properties of the OSCs.