Optimizing Photovoltaic Performance through Functional End‐Capping Units of Polymer Donor Materials

Abstract Advancing the photovoltaic performances of organic solar cells (OSCs) is vital for commercialization. High‐performance OSC active layers commonly comprise polymer donors and small molecule acceptors. Enhanced crystallinity, ordered molecular packing, and strong intermolecular interactions in polymer donors can improve carrier mobility and photovoltaic performance. This study introduces a new polymer, D18‐6F, synthesized using 2‐(3,4,5‐trifluorophenyl)thiophene as an end‐capping unit for the high‐performance polymer donor D18. D18‐6F exhibits improved intermolecular interactions, ordered molecular packing, and crystallinity, leading to better miscibility between donor and acceptor components and optimized blend film morphology. Consequently, OSC devices based on D18‐6F achieved a power conversion efficiency of 19.45%, up from 18.47% (D18). This research offers a valuable strategy for designing high‐efficiency polymer donor materials.