双钙钛矿材料体系的开发及其光伏器件的研究

There are two major problems that perovskite solar cells should face if they are put into practical applications: the toxicity of lead and the stability of perovskite materials. Therefore, to develop lead-free and high stability of the new material is the key way to solve these two problems. Guided by elements´ principle of electron configuration and ionic radius ratio, this project plans to synthesize variety of lead-free systems based on double perovskite materials A2BB´X6. Determine the structure of materials and test their optical properties by comprehensive use of XRD, UV-vis, UPS and DFT technique. Through the thin-film post-processing and ion exchange process, optimize the films of perovskite and effectivly control perovskite uniform nucleation and growth, and avoid the formation of the metastable structures of perovskite films, so as to effectively solve the attenuation of device life caused by morphology change. At the same time, choose the energy level matching charge transport layers, and build high-performance devices. This project combined with the material design, preparation and devices optimization, is expected to obtain high stability and eco-friendly of double perovskite materials and the corresponding devices, and pay the way for the design of new perovskite materials.

钙钛矿太阳能电池要投入实际应用面临两大问题：铅的毒性和钙钛矿材料的稳定性。因此开发无铅和较高稳定性的新材料是解决这一问题的出路所在。本项目以元素的电子构型和离子半径比的原则为指导，拟合成多种基于无铅体系的双钙钛矿材料A2BB´X6；综合利用XRD、UV-vis、UPS和DFT等技术，确定材料的结构，测试其光学性能，并通过薄膜后处理和离子交换等工艺优化钙钛矿薄膜，有效控制钙钛矿形核和均匀生长，避免钙钛矿薄膜亚稳态结构的形成，从而有效解决由于形貌变化造成的器件寿命的衰减；同时，选择能级匹配的电荷传输层，构建高性能的器件。本项目结合材料设计、制备与器件优化，有望得到一批具有较高稳定性和环境友好的双钙钛矿材料及相应的器件，并为新钙钛矿材料的设计提供值得借鉴的思路。

钙钛矿太阳能电池的商业化面临两个障碍，铅的毒性和器件的稳定性。本项目的开展就是为了推进钙钛矿太阳能电池早日商业化，努力尝试解决钙钛矿材料无铅化的基础问题。随着研究工作的实施，我们制备了基于Bi的Cs2CuBiI6 和 Cs3Bi2I9 两种双钙钛矿材料。我们组装器件，多次优化，基于这两种钙钛矿材料的性能都很低（< 1%），一直没有实现突破。经过分析，我们发现其电流受限于材料中的电荷传输方向；电压和填充因子受限于不均匀的薄膜。同时，我们对传统钙钛矿材料进行改善，比如用金属铯取代部分甲胺或者甲脒离子掺杂钙钛矿材料，可以大大提升材料的稳定性，同时可以明显改善电池的光电性能；通过有机阳离子组分调节（甲胺和甲脒离子），制备高性能的器件；利用原位异质结工程策略来构建1D-FAPbI3（deta-）改性3D-MAPbI3钙钛矿结构（1D/3D），进一步提高器件的性能和稳定性。相应的成果分别发表在J Mater. Chem. A, 2017 , 5(10)：4803-4808; Angew.Chem. In. Ed., 2017, 56(26)：7674-7678, Sol. RRL, 2017, 1(9): 1700076 和Adv. Mater., 2018, 30(22)：1707143上。