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In the development of high‐performance organic solar cells (OSCs), the self‐organization of organic semiconductors plays a crucial role. This study focuses on the precisely manipulation of molecular assemble via tuning alkyl side‐chain topology in a series of low‐cost nonfused‐ring electron acceptors (NFREAs). Among the three NFREAs investigated, DPA‐4, which possesses an asymmetric alkyl side‐chain length, exhibits a tight packing in the crystal and high crystallinity in the film, contributing to improved electron mobility and favorable film morphology for DPA‐4. As a result, the OSC device based on DPA‐4 achieves an excellent power conversion efficiency of 16.67 %, ranking among the highest efficiencies for NFREA‐based OSCs. [ABSTRACT FROM AUTHOR]

Moving one subunit of the central core to the other side in a small‐molecule acceptor (SMA) is an effective approach to achieve the goal of isomerization, which has proven viable to enhance photovoltaic performance. Herein, two isomeric SMAs of ThPy5 and ThPy6 are developed by changing the position of the thiophene unit of the dithieno[3,2‐b:2′,3′‐d]pyrrol in IDTP‐4F. The effect of altering the thiophene position on morphological characteristics, macroscopic factors, and device performance is thoroughly investigated among these three isomeric SMAs. Compared to ThPy5, IDTP‐4F and ThPy6 show planar molecular structures and better molecular orientation. Moreover, tighter π–π stacking as well as enhanced electron mobility is observed in ThPy6 relative to IDTP‐4F. PM6:ThPy6‐based organic solar cells (OSCs) achieve the maximum efficiency of 16.11%, along with an excellent fill factor (FF) of 0.789, which are among the best results for A‐D‐A‐type SMA‐based OSCs. The high FF ascribes to the improved molecular packing and charge collection/extraction efficacy and the reduced charge recombination. The structure–morphology–performance relationship drawn from this work can offer better guidance for designing the molecular structure, especially the central cores of SMAs. [ABSTRACT FROM AUTHOR]