Relative to the increase of open-circuit voltage and short-circuit current, promoting fill factor (FF) of the polymer solar cells (PSCs) seems to be more challenging. Here, we designed and synthesized two asymmetrical small molecule acceptors (IDT6CN-M and IDT8CN-M) with large dipole moments. We find that the strong intermolecular interaction and favorable antiparallel packing induced by the dipole moment can effectively enhance both lamellar packing and π–π stacking. The PSCs based on PBDB-T:IDT6CN-M and PBDB-T:IDT8CN-M achieved FFs of up to 76.1% and 78.9%, corresponding to PCEs of 11.23% and 12.43%, respectively. To the best of our knowledge, 78.9% FF is a new record for nonfullerene PSCs. Overall, our work provides a simple and effective molecule-designing method to promote FF of nonfullerene PSCs.

中文翻译：

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使非富勒烯聚合物太阳能电池的填充系数接近79％的不对称小分子受体

相对于开路电压和短路电流的增加，提高聚合物太阳能电池（PSC）的填充因子（FF）似乎更具挑战性。在这里，我们设计并合成了两个具有大偶极矩的不对称小分子受体（IDT6CN-M和IDT8CN-M）。我们发现，偶极矩引起的强烈的分子间相互作用和良好的反平行堆积可以有效地增强层状堆积和π-π堆积。基于PBDB-T：IDT6CN-M和PBDB-T：IDT8CN-M的PSC的FF分别高达76.1％和78.9％，分别对应于PCE分别为11.23％和12.43％。据我们所知，非富勒烯PSC的新记录为78.9％。总体而言，我们的工作提供了一种简单有效的分子设计方法来促进非富勒烯PSC的FF。