面向高效率小分子给体/聚合物受体型有机太阳电池的活性层材料设计和性能研究

During the past few years, the power conversion efficiencies of all small molecule-, all polymer-, and polymer donor/small molecule acceptor-based organic solar cells have been greatly improved. However, the efficiencies of small molecule donor/polymer acceptor (SD/PA)-based devices are significantly lower than those of the three blend systems mentioned above, and how to realize the improvement of the device performance is still unknown. Therefore, exploring and solving the main issues in SD/PA-type photovoltaic devices will overcome the blind spots in organic photovoltaic research, and provide new possibility to solve the problems, like the strong dependence of device performance on the film thickness for the recently reported high-efficiency blend systems. In this project, we will conduct in-depth investigations on photoactive material design and device fabrication method, aiming at solving multiple key issues related to the SD/PA-type devices. Specifically, new polymer acceptors with both high film absorption coefficient and electron mobility will be designed and synthesized, and newly designed small molecule donors that matched with the polymer acceptor will be synthesized. The blend morphology will be optimized by changing the aggregation effect of electron donor and electron acceptor, and the principle of selecting photoactive materials with matched aggregation effect will be obtained from the systematic studies. Based on the new materials and the new morphological optimization method, the efficiency of SD/PA-type device will be significantly improved.

近年来，全小分子、全聚合物和聚合物给体/小分子受体型有机太阳能电池的光伏效率均取得快速突破，但小分子给体/聚合物受体（SD/PA）体系的光伏效率显著低于上述三类体系，且如何实现该类器件光伏效率的提升尚未可知。因此，探索并解决SD/PA型光伏器件效率低下的问题，将打破本领域的研究盲区，并在解决现有高效率体系的性能对膜厚较为敏感等问题方面具有潜在可能。本项目拟针对SD/PA型器件光伏效率提升所面临的关键问题，进行光活性层材料的设计合成和器件研究，即设计合成兼具高消光系数和高迁移率的受体聚合物；从相容性、分子取向和偶极作用三方面，制备与受体聚合物相匹配的给体小分子；通过调控给受体材料的溶液聚集效应实现共混薄膜形貌的优化，并获得构筑高效SD/PA型器件的给受体材料聚集特性的匹配原则。基于上述工作，本项目将推进SD/PA型有机太阳能电池光伏效率的大幅提升，达到与上述三类光伏器件相当的水平。

小分子给体/聚合物受体体系作为有机光伏电池的重要组成，一直面临体系发展缓慢、光伏性能落后的困境。探索并解决这一问题对于打破本领域的研究盲区和推动有机光伏电池全面发展具有重要意义。本项目首先针对该体系中材料相对缺乏且性能尚有不足的现状，设计合成了具有高迁移率的小分子给体和具有高电致发光效率的聚合物受体，从而提高了光伏器件的膜厚耐受性和降低了器件电压损失；其次，从材料的相容性和成膜过程的聚集能力两方面，阐明导致小分子给体/聚合物受体共混形貌差异的成因，并建立起薄膜形貌特征与器件光伏性能之间的关系；最后，通过加工工艺的探索，实现了对小分子给/聚合物受体多尺度形貌的协同优化，相关光伏器件取得能量转换效率的大幅提升。本项目研究结果不仅推动了小分子给体/聚合物受体体系的光伏性能提升，而且对于其他三类体系的材料发展和形貌调控具有重要借鉴意义。