It is widely recognized that subtle changes in the chemical structure of organic semiconductors can induce dramatic variations in their optoelectronic properties and device performance, especially for the nonfullerene small‐molecule acceptors (SMAs). For instance, halogenation of the end groups in the acceptor–donor–acceptor‐type SMAs is an effective strategy to modulate the properties of the end group and thus the entire SMA. While previous position modulations have focused on only one substituent, this study shows the development of three isomeric SMAs (BTP‐ClBr, BTP‐ClBr1, and BTP‐ClBr2) via manipulating the position of two halogen substituents (chlorine and bromine) on the terminal unit. BTP‐ClBr exhibits a blueshifted absorption, a shallower lowest unoccupied molecular orbital energy level, and a weaker crystallization tendency relative to BTP‐ClBr1 and BTP‐ClBr2. A power conversion efficiency (16.82%) and an excellent fill factor (FF) (0.79) are realized in the optimal PM6:BTP‐ClBr organic solar cell device. The higher FF is consistent with the results of the characterization including a longer charge recombination lifetime, a faster photocurrent decay, a weaker bimolecular recombination, and a more favorable domain size for PM6:BTP‐ClBr, which all originate from a subtle change in the substitution sites that strongly influences the physicochemical properties of the SMA.

中文翻译：

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改变端基上氯和溴取代的位置可实现高性能受体和高效的有机太阳能电池

众所周知，有机半导体化学结构的细微变化会引起其光电特性和器件性能的巨大变化，尤其是对于非富勒烯小分子受体（SMA）。例如，受体-供体-受体型SMA中端基的卤化是调节端基以及整个SMA性能的有效策略。尽管以前的位置调节只集中在一个取代基上，但这项研究表明，通过操纵末端的两个卤素取代基（氯和溴）的位置，发展了三种同分异构的SMA（BTP-ClBr，BTP-ClBr1和BTP-ClBr2）。单元。BTP-ClBr表现出蓝移吸收，较浅的最低未占据分子轨道能级，与BTP-ClBr1和BTP-ClBr2相比，结晶趋势更弱。最佳的PM6：BTP-ClBr有机太阳能电池器件实现了功率转换效率（16.82％）和出色的填充因子（FF）（0.79）。较高的FF与表征结果一致，包括更长的电荷重组寿命，更快的光电流衰减，更弱的双分子重组以及更有利的PM6：BTP-ClBr畴尺寸，这些都源自微细的变化。强烈影响SMA物理化学性质的取代位点。