A highly crystalline non-fused ring small-molecule acceptor as a third component significantly enhances the efficiency of all-polymer solar cells

Abstract

All-polymer solar cells (all-PSCs) have received tremendous focus recently owing to their superior mechanical robustness and excellent thermal stability. However, only few studies on the application of small-molecule acceptors (SMAs) in all-PSCs have been reported. Herein, a highly crystalline non-fused ring (NFR) SMA, namely DFTQA-2FIC, was introduced as a third component to enhance the performance of an all-PSC based on PBDB-T:N2200. After introducing DFTQA-2FIC into the PBDB-T:N2200 blend, the energy levels of DFTQA-2FIC did not only cascade with those of PBDB-T and N2200, but also formed a more uniform and continuous interpenetrating structure and caused better phase separation, thereby mitigating losses caused by electron–hole recombination, minimizing energy dissipation, and significantly elevating charge transport with a well-balanced performance. Encouragingly, an impressively improved power conversion efficiency (PCE) from 6.45% in binary all-PSCs to 8.07% in the ternary system, with an increase of 25.1%, was obtained, which is one of the highest reported for PBDB-T:N2200-based all-PSCs thus far. This study highlights the potential of this type of NFR-SMA as a third component for highly efficient ternary OSCs.