多功能离子型苝二酰亚胺类电子传输材料的结构调控及其在钙钛矿太阳能电池中的性能研究

Recently, inverted planar structured perovskite solar cells (PSCs) receive growing interest due to the advantages of low temperature processability and hardly any current density-voltage (J-V) hysteresis effects. Typically, in inverted planar PSCs, fullerene (C60) and its derivatives (PC61BM, PC71BM and ICBA) have commonly been employed as electron transport materials (ETMs). However, fullerene derivatives suffer from certain drawbacks, such as limited flexibility of energy levels, costly production processes, poor stability and so on. Therefore, in this project, the main ambition is to overcome the drawbacks of the traditional fullerene derivatives used as ETMs for PSCs. A new strategy to design non-fullerene ETMs is presented by molecular engineering to include charged moieties in the ETM. The influence of core building blocks, the ionization positions, the position and number of hydrophobic alkyl chains and cross-linking groups of ETMs on devices’ photovoltaic performance and materials’ properties, such as energy levels, electron mobility and conductivity, will be systematically studied; and the structure-activity relationship between them will be established. Moreover, the self-assembly mechanism between multi-functional ETMs and perovskite, and the electron transport properties of PSCs will be further discussed to reveal the main limiting factor on PCE and stability of the devices. The ways to improve the device PCE and stability will be finally proposed. The implementation of this project will supply both theoretical and methodological guidance for design and fabrication of low cost, high efficiency, high stability ETMs for the PSCs.

反式平面型钙钛矿太阳能电池由于可低温溶液制备且测试过程中无迟滞现象，近年来获得了学术界的高度关注。本项目针对反式平面型钙钛矿太阳能电池中富勒烯类电子传输材料成本高、能带结构难以调节、稳定性差等问题，提出利用分子工程手段，导向性设计开发一系列能级可调、电子迁移率及导电性高、稳定性好的离子型苝二酰亚胺类电子传输材料并应用于钙钛矿太阳能电池。通过对分子材料的核心结构、离子化的位置、柔性烷基链及交联基团的位置和个数的调整，优化分子构型，研究材料的载流子迁移率、导电性及其应用于钙钛矿太阳能电池的光电转换性能及稳定性，阐明电子传输材料分子构型与材料性能之间的构效关系；同时深入分析离子型电子传输材料与钙钛矿材料界面自组装保护机理及界面电子传输规律，阐明钙钛矿太阳能电池效率及稳定性的限制性因素，寻求提升电池效率和稳定性的有效方法，并为钙钛矿太阳能电池在高效电子传输材料方面提供新的选择。

本项目针对反式平面型钙钛矿太阳能电池中富勒烯类电子传输材料成本高、能带结构难以调节、稳定性差等问题，提出利用分子工程手段，通过核心结构及外围功能化取代基调控，设计开发了一系列能级可调、电子迁移率及导电性良好、稳定性高的非富勒烯类电子传输材料，并成功应用于钙钛矿太阳能电池，获得了>21%的光电转换效率；揭示了电子传输材料分子构型与材料性能之间的“构效关系”；阐明了多功能化电子传输材料与钙钛矿材料界面自组装缺陷钝化及增效电子传输的作用机制；提出了设计开发高性能非富勒烯电子传输材料的新策略，并实现了基于非富勒烯电子传输传输材料的钙钛矿太阳能电池效率与稳定性的双提升。此外，在本项目的资助下，同时开展了空穴传输层调控方面的工作，设计开发了一系列低成本、高效率的新型空穴传输材料，获得了>23%的光电转换效率。研究工作的顺利开展，为钙钛矿太阳能电池在高效率、低成本电子/空穴传输材料方面提供了新的选择。