Fine‐Tuning Batch Factors of Polymer Acceptors Enables a Binary All‐Polymer Solar Cell with High Efficiency of 16.11%

Abstract Random conjugated polymers, such as typical polymerized small molecular acceptors (PSMAs), concurrently suffer from the dual batch factors of molecular weights (MWs) and regioregularity, which seriously interfere with the study of the relationship between batch factors and polymer properties. Here, four isomer‐free PSMAs, PA‐5 and three members of a PA‐6 series with low (L), medium (M), and high (H) MWs, in which 5 and 6 define linkage position throughout conjugated backbone, are designed and synthesized to clearly investigate polymer batch effects. These studies reveal that PA‐6‐L and PA‐6‐M have ignorable batch differences within deviations, which deliver comparable maximum efficiencies of 14.81% and 14.99%, respectively. The PA‐6‐H based cell is processed from chlorobenzene with its high boiling point, due to the limited solubility in other common solvents, leading to large‐size phase separation during prolonged film drying process, and thereby inferior performance. In contrast, PA‐5 possesses diverse absorption characteristics, and ordered crystallization, which prompts higher short‐circuit current density and fill factor in the cell. As a result, the corresponding device realizes a photovoltaic performance of 16.11%, which is one of the best binary all‐polymer solar cells in the reported literature to date. This study provides a new insight into complicated batch effects of PSMAs on device performance while avoiding cross‐talk between them.