Chlorine-substituted conjugated polymers not only possess simple and high-yield synthetic steps due to the cheap raw materials available for their synthesis but also exhibit great potential for the commercial application of polymer solar cells (PSCs) with excellent photovoltaic performance. However, the current research of chlorine-substituted donor polymers is lagging compared to the rapid development of chlorinated acceptors. Here, a chlorine-free polymer PTBT and a chlorinated donor polymer PTBT-Cl were prepared and studied in parallel. The chlorine-substituted polymer PTBT-Cl showed a much lower highest occupied molecular orbital (HOMO) level value of 5.46 eV and an enhanced aggregation behavior in film, achieving an optimized phase separation morphology in blend with an efficient acceptor compared with that of PTBT. Surprisingly, the chlorine-free PTBT-based PSCs showed a negligible power conversion efficiency (PCE) of 3.88%, while the PTBT-Cl exhibited a decent PCE of 12.31%, with a simultaneously increased short circuit current density (J_sc) of 23.73 mA cm^–2 and a fill factor (FF) of 62.53%, when matched with the fused-ring electron acceptor (FREA) Y6. This work provides new insight into the economical design and synthesis of chlorine-substituted polymers, boosting the photovoltaic performance of PSCs.

中文翻译：

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共轭侧链的氯化作用可增强分子间的相互作用，从而提高太阳能转化率

氯取代的共轭聚合物不仅因其可用于合成的廉价原料而具有简单且高产率的合成步骤，而且对于具有优异光伏性能的聚合物太阳能电池（PSC）的商业应用也显示出巨大的潜力。但是，与氯化受体的快速发展相比，目前对氯取代的供体聚合物的研究滞后。在此，制备并平行研究了无氯聚合物PTBT和氯化供体聚合物PTBT-Cl。氯取代的聚合物PTBT-Cl显示出更低的最高占据分子轨道（HOMO）水平值为5.46 eV，并且膜中的聚集行为得到增强，与PTBT相比，在与有效受体混合的情况下实现了优化的相分离形态。出奇，与稠环电子受体（FREA）Y6匹配时，J _sc）为23.73 mA cm ^–2，填充系数（FF）为62.53％。这项工作为氯取代聚合物的经济设计和合成提供了新的见识，从而提高了PSC的光伏性能。