Despite recent progress in tailoring the molecular packing of donor–acceptor (D–A) copolymers in the solid state, studies on their solution-state aggregation and the dependence of the solid-state packing on solution aggregates remain to be clearly understood. Herein, we outline the relationship between the solution aggregates and solid-state crystal orentation in a specific class of D–A copolymers, i.e., 5,6-difluoro-4,7-bis(thiophen-2-yl)-2,1,3-benzothiadiazole (FBTT) units connected to bithiophene (2T) or thienothiophene (TT), by adjusting both the intrinsic (i.e., backbone planarity) and extrinsic factors (i.e., solvent) and investigate the influence of these structures with different crystal orientations on the organic field-effect transistor (OFET) performance. Remarkably, both PFBTT-2T and PFBTT-TT weakly aggregate in good solvents, forming face-on crystals in solid-state films. In contrast, they aggregate more strongly in relatively poor solvents and form edge-on crystals in films. When thin films are produced from the same solvent chlorobenzene (CB), PFBTT-2T with reduced planarity adopts face-on orientation, whereas PFBTT-TT with greater planarity adopts edge-on orientation. Moreover, the charge transport properties of both polymers strongly correlate with their various crystalline orientations. This work comprehensively elucidates how FBT-based polymers aggregate and pack in the solution and solid states and how these processes and electrical properties can be controlled by tuning the solvent quality and molecular structure.

中文翻译：

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溶液态聚集对供体-受体共轭共聚物中固态晶体取向的影响

尽管最近在定制固态供体-受体（D-A）共聚物的分子堆积方面取得了进展，但对其溶液态聚集以及固态堆积对溶液聚集体的依赖性的研究仍有待清楚了解。在此，我们概述了特定类别的 D-A 共聚物（即 5,6-二氟-4,7-双（噻吩-2-基）-2,1）中溶液聚集体和固态晶体取向之间的关系通过调整内在因素（即主链平面度）和外在因素（即溶剂），将 ,3-苯并噻二唑（FBTT）单元连接到联噻吩（2T）或噻吩并噻吩（TT），并研究不同晶体取向的这些结构的影响有机场效应晶体管（OFET）的性能。值得注意的是，PFBTT-2T 和 PFBTT-TT 在良溶剂中均弱聚集，在固态薄膜中形成面状晶体。相反，它们在相对较差的溶剂中聚集得更强烈，并在薄膜中形成边缘晶体。当使用相同的溶剂氯苯（CB）生产薄膜时，平面度降低的PFBTT-2T采用正面取向，而平面度较高的PFBTT-TT则采用边缘取向。此外，两种聚合物的电荷传输特性与其不同的晶体取向密切相关。这项工作全面阐明了基于 FBT 的聚合物如何在溶液和固态中聚集和堆积，以及如何通过调整溶剂质量和分子结构来控制这些过程和电性能。