平面型五环苯并稠合噻吩同分异构体的OFET性能研究

Organic field-effect transistors (OFETs) have potential applications in low-cost and large-area flexible electronics, but the low mobility limits their practical application. The derivatives of benzothiophene as organic semiconductor possess high mobilities, which may be further improved by replacing the thiophene unit with fused thiophenes. In this project, we plan to synthesize a series of five-membered benzo-fused thienothiophene isomers with planar structure and systematically study their OFET properties. The effects of molecular scaffolds with benzene units changing and the S atoms with quality and positions changing, on the intermolecular interaction and the molecular arrangement, the energy levels of these materials and the habits of films growth, and the field effect mobility and devices stability, will be mainly investigated. The relationship between molecular scaffolds and the properties of OFETs will be systematically studied from macroscopic aspect. Combing with the theoretical calculations, the correlation between the quality and positions of S atoms and the intermolecular interactions and carriers transporting will be investigated from microcosmic aspect. We wish to get some organic semiconductors with high mobility, and expect this project will be helpful to provide the academic basis and application materials for seeking the relationship between molecular structures and their properties, and generate a new research perspective for studying the carrier transport in organic semiconductors.

有机场效应晶体管在低成本、可大面积加工的柔性电子产品中具有潜在的应用前景，但迁移率较低一直是制约其实际应用的瓶颈。苯并噻吩衍生物是一类高迁移率有机半导体材料，如果将其噻吩结构单元替换为具有多种分子间作用力的稠合噻吩可能会进一步提高其迁移率。本项目拟设计合成一系列平面型五环苯并稠合噻吩同分异构体，旨在系统地研究其OFET性能，考察苯环单元数变化引起的分子骨架不同以及S原子数量和位置不同时:1)对分子间作用力和分子堆积方式的影响；2）对材料能级和薄膜生长习性的影响；3）对材料的场效应迁移率和稳定性的影响。从宏观上探寻材料的分子结构与其OFET性能之间的内在联系和规律，同时结合理论计算从微观上探讨S原子数量和位置对分子间作用力和载流子输运特性的影响规律。希望该项目的实施能够得到一批高迁移率的有机半导体材料，为探寻其构效关系提供理论依据和应用素材，为深入研究其载流子输运机制提供一个新的角度。

OFET在低成本、可大面积加工的柔性电子产品中具有潜在的应用前景，目前已报道的高迁移率有机半导体材料多数都是苯并噻吩衍生物，但迁移率较低一直是制约其实际应用的瓶颈。无机半导体材料以强的共价键结合形成有序的结构，而有机半导体材料是由弱的分子间作用力结合在一起。因此我们认为这种结合方式的差别是有机半导体材料迁移率低的本质原因。本项目从增强分子间作用力来提高有机半导体材料迁移率的角度出发，以稠合噻吩来代替苯并噻吩衍生物中的单噻吩结构单元，设计合成了三个系列31种五元稠环苯并稠合噻吩同分异构体。从分子骨架、S原子位置、分子间作用等角度，结合单晶结构和理论计算，系统研究分析了分子结构与其OFET性能之间的内在联系和规律。研究结果表明：1）并五噻吩同分异构体的OFET性能优于苯并四噻吩同分异构体，苯并四噻吩同分异构体的OFET性能优于萘并三噻吩；2）含有连续噻吩单元结构五环苯并稠合噻吩同分分异构体中S原子整体参与共轭的程度较高，π-π间距较小，同时在多个方向上存在S--S相互作用，当S--S相互作用与π-π相互作用不在同一个方向时，分子间作用力中对载流子传输的贡献程度为S-S > S-C/π- π > C-C。