Design and Synthesis of Acceptor-Donor-Acceptor Type Non-Fullerene Acceptors Using Oxindole-Based Bridge for Polymer Solar Cells Applications

Two acceptor-donor-acceptor (A-D-A) type non-fullerene acceptors (namely WH1 and WH7) containing the oxindole-based bridge are designed and synthesized for polymer solar cells(PSCs) applications. The bridge unit is introduced through a precursor (6-bromo-1-octylindoline-2, 3-dione) that contains both bromine and carbonyl and provides the feasibility of the Pd-catalyzed cross-coupling reaction and the Knoevenagel condensation, respectively. This facile synthetic approach exhibits the potential to gain high performance non-fullerene acceptors through extending π-conjugated backbone with strong light-absorbing building blocks. The synthesis and properties of WH1 and WH7 are demonstrated with different endcap units, then PSCs are fabricated using PBDB-T:WH1 and PBDB-T:WH7 as the active layers, and attain an average power conversion efficiency ( PCE) of 2.58％ and 6.24％, respectively. Further device physics studies afford the deep insight of structure variation influence on the device performance. This work provides a facile non-fullerene acceptor design strategy and shows how structure variations impact the PSC performance.