Polymerized Small-Molecule Acceptors for High-Performance All-Polymer Solar Cells

All-polymer solar cells (all-PSCs) have drawn tremendous research interest in recent years, due to their inherent advantages of good film formation, stable morphology, and mechanical flexibility. The most representative and most widely used n-CP acceptor was the naphthalene diimide based D-A copolymer N2200 before 2017, and the power conversion efficiency (PCE) of the all-PSCs based on N2200 reached over 8% in 2016. However, the low absorption coefficient of N2200 in the near-infrared (NIR) region limits the further increase of its PCE. In 2017, we proposed a strategy of polymerizing small-molecule acceptors (SMAs) to construct new-generation polymer acceptors. The polymerized SMAs (PSMAs) possess low band gap and strong absorption in the NIR region, which attracted great attention and drove the PCE of the all-PSCs to over 15% recently. In this Minireview we explain the design strategies of the molecular structure of PSMAs and describe recent research progress. Finally, current challenges and future prospects of the PSMAs are analyzed and discussed.