高载流子迁移率有机热电材料的设计合成及其热电性能研究

Considering the serious problems such as energy shortage and environmental pollution, thermoelectric (TE) materials can convert the temperature gradient into electric power, so it can be used to recycle waste heat to generate electricity, which is of great importance to improve the fossil fuels efficiency and reduce environmental pollutions. Therefore, organic thermoelectric materials are attracting broad attention from the scientific and industrial communities owing to its remarkable potential applications in processing lightweight, mechanically flexible and portable/wearable micro-thermoelectric devices. However, because of the low electrical conductivity and unclear structure information, existed organic thermoelectric materials usually show relatively low thermoelectric conversion efficiency and unclear structure-property relationships. Therefore, in order to develop high performance organic thermoelectric materials with high carrier mobility and electrical conductivity, this project designs a series of novel organic materials, such as conjugated polymers, organometallic coordination polymers and conjugated molecules based on functionalized dibenzothiophene and tetrathiafulvalene. By precisely controlling the doping conditions and performing theoretical calculations, this project will also investigate the effects of the carrier density, electronic band structure and stacking model on the properties, such as electrical conductivity, Seebeck coefficient and thermal conductivity, which will shed light on the relationships between the material composition, structure and thermoelectric properties. In short, the ultimate aim of this project is to develop novel high-performance organic thermoelectric materials and explore the charge and thermal transport mechanisms, which holds great theoretical value and practical significance in promoting organic thermoelectrics applications.

面对能源短缺、环境污染等重大问题，热电材料可以实现热能直接转换为电能、利用废热发电，对提高化石能源利用效率、减少环境污染具有重大意义。有机热电材料在制备质轻、柔性、可穿戴微型热电器件方面的独特优势引起了科学界及企业界广泛关注。但是，目前有机热电材料研究存在高性能材料体系少、结构信息不清晰、结构与性质间关系不明确等问题。本项目从提高材料载流子浓度和迁移率两个基本点出发，通过对苯并二噻吩和四硫富瓦烯等基团进行功能化修饰合成一系列共轭聚合物、金属有机配位聚合物及共轭小分子等，优化掺杂条件，发展高性能有机热电材料新体系；并在此基础上，研究其载流子浓度、能带结构、堆积方式等对电导率、Seebeck系数、热导率的影响，深入探究材料组成、结构与热电性能之间的关系。本项目旨在发展新型高性能有机热电材料，探索其内部电荷传输机理、热传输机制等问题，对推动有机热电器件商品化应用具有十分重要的理论价值和实际意义。

在实现碳达峰与碳中和“双碳”目标的所有途径中，发展新型环境友好的可再生能源及能源转换技术是重点突破方向。有机半导体材料在以溶液湿法制备质量轻、柔性可折叠甚至可卷曲的低成本电子器件方面具有独特的优势。但是，无论是应用于将热能直接转换为电能有机热电材料，还是将电能转换为光能有机电致发光材料，都面临能源转换性能较低的关键问题。本项目通过设计新型有机共轭小分子、有机聚合物以及有机金属配合物等手段开发具有电荷传输能力强、发光效率高、热稳定性能好等优点的有机半导体材料，根据材料性质特点制备有机热电器件或者有机电致发光器件，研究其能源转换性能。本项目成功合成得到15个有机共轭小分子、2个聚合物以及20个有机金属配合物材料，表征鉴定了它们的结构信息、热稳定性、基本光物理性质、基本电化学性质以及热电或者电致发光性质，同时利用理论计算对相关实验结果进行深入探究，建立结构与性能之间的关系。在有机共轭小分子中，通过掺杂可将TTFEDOTCN的电导率提高到4 S/cm，最终实现了功率因子3.33 μW/mK2 (300 K)；在聚合物中，通过掺杂P1聚合物能够实现功率因子高达86 μW/mK2的优异热电性能；在有机金属配合物中，实现最大外量子效率为25.8%的深红电致发光，最大外量子效率为22.4%的高色纯度黄色电致发光。这些热电性能或者电致发光性能在同类别类似条件下处于最好之列。本项目的研究结果表明，四硫富瓦烯基团有利于提升热电性能，多金属中心结构有利于增强电致发光效率。因此，本项目的研究成果为发展新型高效有机热电以及有机电致发光等能源转换有机半导体材料提供了新思路。