Backbone planarity is an inherent structural feature for fused ring electron acceptors and one of important prerequisites for their high photovoltaic performance. However, for non-fused ring electron acceptors (NFREAs), it is a challenging task to achieve it. In this work, two NFREAs ( and ) containing thiophene-benzene-thiophene or thiophene-benzothiadiazole-thiophene three non-fused aromatic rings in central scaffold were designed with an attempt to use a pair of 2,4,6-triisopropylphenyl substituents (referred as “embracing”-type side chains) at 3,3′-positions of the two thiophene units to lock the backbone in a planar conformation. X-ray crystallography revealed that has a quasi-planar backbone, whereas shows a twisted one, but both tend to form two-dimensional layered arrays through intermolecular π-π stacking involving terminal acceptor moieties. UV–vis light-absorption spectroscopy showed that both compounds have similar optoelectronic properties either in dilute solutions or in solid film state, thus confirming the conformation-lock function of the “embracing”-type side chains. While for photophysical properties, displays a red-shifted broader light absorption spectrum as compared to due to the introduction of an additional acceptor moiety in the structure. and were evaluated as the acceptor materials in organic solar cells in combination with , a typical donor polymer, and delivered the optimized power conversion efficiencies of 4.31 % and 3.78 %, respectively. Although the photovoltaic performances are modest, the work provides a new thought for maintaining the backbone planarity in NFREAs and would be useful in their future design.

中文翻译：

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有机太阳能电池用“环抱型”侧链非稠环电子受体设计


主干平面性是稠环电子受体的固有结构特征，也是其高光伏性能的重要先决条件之一。然而，对于非稠环电子受体（NFREA）来说，实现它是一项具有挑战性的任务。在这项工作中，设计了两个在中心支架中含有噻吩-苯-噻吩或噻吩-苯并噻二唑-噻吩三个非稠合芳环的NFREA（和），并尝试使用一对2,4,6-三异丙基苯基取代基（称为作为“拥抱”型侧链）位于两个噻吩单元的 3,3'-位置，将主链锁定在平面构象中。 X射线晶体学显示其具有准平面主链，而显示出扭曲主链，但两者都倾向于通过涉及末端受体部分的分子间π-π堆积形成二维层状阵列。紫外可见光吸收光谱表明，两种化合物无论在稀溶液还是在固膜状态下都具有相似的光电性质，从而证实了“拥抱”型侧链的构象锁定功能。而对于光物理性质，由于在结构中引入了额外的受体部分，因此显示出红移的更宽的光吸收光谱。并与典型的供体聚合物结合作为有机太阳能电池中的受体材料进行评估，并分别提供了 4.31% 和 3.78% 的优化功率转换效率。尽管光伏性能不高，但这项工作为保持 NFREA 的主干平面性提供了新的思路，并将对其未来的设计有用。