Small Molecule Acceptors with a Nonfused Architecture for High-Performance Organic Photovoltaics

Different from the widely studied non-fullerene acceptor molecules with a generally large fused backbone architecture, two novel small molecule acceptors (SMAs) with a nonfused architecture, namely, BDTS-4Cl and BDTC-4Cl, have been designed and synthesized with much simpler procedures using dithienosilole (DTS) and cyclopentadithiophene (DTC) as the pi donor moieties, respectively. PBDB-T:BDTC-4Cl-based organic solar cells (OSCs) show a power conversion efficiency (PCE) of 9.54% compared to a PCE of 3.73% for PBDB-T:BDTS-4Cl-based OSCs. When using PC71BM as a combinatory acceptor for a ternary system of BDTC-4Cl, the PCE has been enhanced significantly to 12.19%. These results are evidence of the highest-performance OSCs using SMAs with a nonfused framework, comparable to the widely studied large fused SMA-based OSCs. These results indicate that, benefiting from the high diversity of organic molecular structures, further design and studies are urgently needed and also important for exploring and/or optimizing OSC molecules for both better performance and simpler synthesis with different architectures, such as the case presented here with a nonfused architecture.