Enhancing the performance of the electron acceptor ITIC-Th via tailoring its end groups

We choose the high-performance nonfullerene acceptor ITIC-Th as an example, and incorporate electron-donating methoxy and electron-withdrawing F groups onto the terminal group 1,1-dicyanomethylene-3-indanone (IC) to construct a small library of four fused-ring electron acceptors. With this series, we systematically investigate the effects of the substituents on the end-groups on the electronic properties, charge transport, film morphology, and photovoltaic properties of the ITIC-Th series. The electron-withdrawing ability increases from methoxylated to unsubstituted, fluorinated, and difluorinated IC, leading to a downshift of energy levels and a redshift of absorption spectra. Optimized organic solar cells based on the ITIC-Th series show power conversion efficiencies ranging from 8.88% to 12.1%.