“Twisted” small molecule donors with enhanced intermolecular interactions in the condensed phase towards efficient and thick-film all-small-molecule organic solar cells,Journal of Materials Chemistry A

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“Twisted” small molecule donors with enhanced intermolecular interactions in the condensed phase towards efficient and thick-film all-small-molecule organic solar cells
Journal of Materials Chemistry A ( IF 10.7 ) Pub Date : 2023-05-29 , DOI: 10.1039/d3ta01893h
Xiafei Cheng _{1,

2} , Ziqi Liang ₁ , Shifeng Liang ₁ , Xuwen Zhang ₁ , Jie Xu ₁ , Yan Xu ₁ , Wang Ni ₃ , Miaomiao Li ₁ , Yanhou Geng _{1,

4}

Affiliation

How to achieve high crystallinity and suitable phase scale simultaneously from the perspective of molecular engineering remains a long-standing challenge for all-small-molecule organic solar cells (ASM-OSCs). Herein, two small molecule donors, named DRTT-2Se (with two alkylselenophenyl chains) and DRTT-6Se (with six alkylselenophenyl chains), were designed and synthesized by introducing “twisted” backbones and building units with strong intermolecular interactions. The “twisted” skeletons of the molecules can suppress the molecular crystallization and avoid excessive aggregation during the film forming process, while the strong intermolecular interactions of the building units can encourage the formation of ordered molecular packing and nanoscale phase separation via post-treatments. Owing to the enhanced intermolecular interactions induced by alkylselenophenyl side chains, DRTT-2Se and DRTT-6Se with a “twisted” structure displayed more ordered π–π packing, and retained the similar nanoscale microstructures in the blend films in comparison to the “twisted” molecule with alkylthiophenyl side chains (DRTT-T), yielding improved hole transport and reduced charge recombination in OSCs. In addition, the alkylselenophenyl substituted molecules showed higher HOMO energy levels, which caused the larger HOMO offset to drive exciton dissociation, but did not increase the energy loss. As a result, the ASM-OSCs based on the selenophene-containing donors exhibited higher FF and J_sc, and similar V_oc, yielding superior PCEs (14.79% and 15.03%) compared to the DRTT-T based device (13.37%). More importantly, the appropriate film morphology made the device efficiency of DRTT-2Se and DRTT-6Se less sensitive to the thickness of active layers. This study provides some implications in designing small molecule donors with suitable crystallization behavior towards high-performance ASM-OSCs.

中文翻译：

“扭曲”小分子供体在凝聚相中具有增强的分子间相互作用，可用于高效厚膜全小分子有机太阳能电池

如何从分子工程的角度同时实现高结晶度和合适的相尺度仍然是全小分子有机太阳能电池（ASM-OSC）长期面临的挑战。在此，通过引入“扭曲”主链和具有强分子间相互作用的结构单元，设计并合成了两种小分子供体，命名为DRTT-2Se（具有两个烷基硒苯基链）和DRTT-6Se（具有六个烷基硒苯基链）。分子的“扭曲”骨架可以抑制分子结晶，避免成膜过程中的过度聚集，而结构单元的强分子间相互作用可以促进有序分子堆积和纳米级相分离的形成。后处理。由于烷基硒苯基侧链诱导的分子间相互作用增强，具有“扭曲”结构的DRTT-2Se和DRTT-6Se表现出更有序的π-π堆积，并且与“扭曲”结构相比，共混膜中保留了相似的纳米级微观结构。具有烷硫基侧链（DRTT-T）的分子，可改善 OSC 中的空穴传输并减少电荷复合。此外，烷基硒苯基取代的分子表现出更高的HOMO能级，这导致更大的HOMO偏移驱动激子解离，但并没有增加能量损失。结果，基于含硒吩供体的 ASM-OSC 表现出更高的 FF 和J _sc以及相似的V _oc，与基于 DRTT-T 的设备 (13.37%) 相比，产生了更高的 PCE (14.79% 和 15.03%)。更重要的是，适当的薄膜形貌使得DRTT-2Se和DRTT-6Se的器件效率对有源层的厚度不太敏感。这项研究为设计具有适合高性能 ASM-OSC 结晶行为的小分子供体提供了一些启示。

更新日期：2023-05-29

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