Two novel small molecule acceptors (DTNIC6 and DTNIC8) based on a ladder-type dithienonaphthalene (DTN) building block with linear (hexyl) or branched (2-ethylhexyl) alkyl substituents are designed and synthesized. Both acceptors exhibit strong and broad absorption in the range from 500 to 720 nm as well as appropriate highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) levels. Replacing the linear hexyl chains with the branched 2-ethylhexyl chains has a large impact on the film morphology of photoactive layers. In the blend film based on DTNIC8 bearing the branched alkyl chains, morphology with well-defined phase separation was observed. This optimal phase morphology yields efficient exciton dissociation, reduced bimolecular recombination, and enhanced and balanced charge carrier mobilities. Benefited from these factors, organic solar cells (OSCs) based on PBDB-T:DTNIC8 deliver a highest power conversion efficiency (PCE) of 9.03% with a high fill factor (FF) of 72.84%. This unprecedented high FF of 72.84% is one of the highest FF values reported for nonfullerene OSCs. Our work not only affords a promising electron acceptor for nonfullerene solar cells but also provides a side-chain engineering strategy toward high performance OSCs.

中文翻译：

---

用于高效非富勒烯有机太阳能电池的梯型基于二噻吩并萘的小分子受体

设计并合成了两个基于梯形二噻吩萘（DTN）结构单元的新型小分子受体（DTNIC6和DTNIC8），该梯形二噻吩萘具有线性（己基）或支链（2-乙基己基）烷基取代基。两种受体均表现出在500至720 nm范围内的强而宽的吸收，以及适当的最高占据分子轨道（HOMO）和最低未占据分子轨道（LUMO）的水平。用支链的2-乙基己基链取代线性己基链对光敏层的膜形态具有很大的影响。在基于带有支链烷基链的DTNIC8的共混膜中，观察到具有明确相分离的形态。这种最佳的相形态可产生有效的激子解离，减少的双分子重组以及增强和平衡的载流子迁移率。受益于这些因素，基于PBDB-T：DTNIC8的有机太阳能电池（OSC）具有9.03％的最高功率转换效率（PCE）和72.84％的高填充率（FF）。此史无前例的72.84％的高FF是非富勒烯OSC报告的最高FF值之一。我们的工作不仅为非富勒烯太阳能电池提供了有希望的电子受体，而且还为高性能OSC提供了侧链工程策略。