Impact of isomers on the photovoltaic properties of polymerized small-molecule acceptors

All-polymer solar cells(all-PSCs)have attracted tremendous research interests due to their inherent advantages of excellent mechanical flexibility,film formation,and morphological stability.Recently,the development of polymerized small-molecule acceptors(PSMAs)has boosted the power conversion efficiencies(PCEs)of all-PSCs to over 18%.Polymerization sites on the terminal groups of small molecule acceptors play a decisive role in determining the absorption spectra,frontier molecular orbital energy levels,molecular packing and crystallinity,charge carrier mobilities and device performance of polymer acceptors.In this perspective,we focus on the latest advances of region-specific terminal groups and region-regular PSMAs,aiming to summarize the relationship between molecular structure–physicochemical properties–active layer morphology–device performance.Finally,the future design directions and challenges faced by region-specific terminal groups and regionregular PSMAs are discussed.In this Perspective article,we advocate that the region-regular PSMAs approach can advance better designs for high-performance polymer acceptors with good batch-to-batch reproducibility.