拟卤素钙钛矿的可控制备与性能研究

Perovskite solar cells have attracted great interests with respect to their high performance, low cost, and solution processability. However, the spherical shape of iodide ions have weak interaction with methanaminium ions and lead ions, resulting in poor stability of perovskite. Pseudohalides have similar chemical properties to true halides. The linear shape of pseudohalide ions is much stable than the spherical shape of iodide ions. Moreover, the lone pair electrons in pseudohalide ions can interact strongly with the Pb ion, which in turn stabilizes the frame structure of perovskite. Herein, we propose a new concept to replace all halide ion by pseudohalide ion in the frame of the perovskite structure to improve the stability of perovskite. The fabrication of pseudohalide perovskite film and their optoelectronics will be deeply studied. The theoretical work would be first conducted based on pseudohalide ion replaced perovskite structure, giving a guidance for selection of pseudohalide ion by investigating the relationship between the electronic structure of pseudohalide ion and the optoelectronic performance of perovskite structure. In experiments, the pseudohalide perovskite with controllable crystal domain and tunable bandgap will be synthetized and characterized. The high-performance device would finally be fabricated by designing and optimizing the functional layers. We hope we can give a guideline for the stability of perovskite and contribute a lot for the commercialization of perovskite solar cells.

钙钛矿太阳能电池具有高效率、低成本、可溶液加工等特点引起了人们广泛的研究兴趣。然而钙钛矿中球形的卤素离子与甲胺和铅离子的价键作用较弱，导致钙钛矿的稳定性差。拟卤素离子具有与卤素离子相似的化学性质，但其线性结构更加稳定并且孤对电子与铅离子可以形成强的价键结构，为提高钙钛矿结构的稳定性提供了新的思路。本项目拟以钙钛矿的稳定性为导向，通过拟卤素离子全部取代卤素离子，研究拟卤素钙钛矿的可控制备和光电性能。理论计算上细致分析拟卤素离子电子结构与钙钛矿光电性能的关系，为拟卤素离子的选择提供理论指导；实验上制备晶粒尺寸可控、能级结构可调的拟卤素钙钛矿薄膜，探究拟卤素的引入对光生载流子扩散与传输以及薄膜稳定性的影响；在此基础上，通过功能层的设计和优化，最终实现稳定高效的钙钛矿太阳能电池，为解决钙钛矿太阳能电池的稳定性做出有益探索，为推动钙钛矿太阳能电池产业化发展做出一定贡献。

钙钛矿太阳能电池具有高效率、低成本、可溶液加工等特点引起了人们广泛的研究兴趣。然而钙钛矿的稳定性较差，是其商业化必须要解决的问题。本项目以钙钛矿的稳定性为导向，通过拟卤素离子取代卤素离子，设计拟卤素钙钛矿，以提升钙钛矿的薄膜和器件的稳定性。我们通过硫氰酸铵（NH4SCN）引入拟卤素SCN-离子，NH4+和SCN-之间的协同效应，有利于控制晶核的形成、晶粒的生长、晶粒尺寸的调控和薄膜的稳定性。相比与单一离子作为添加剂的器件，含有NH4+的NH4I（13.97%）和含有SCN-的Pb(SCN)2（12.88%），基于NH4SCN添加剂的器件效率（16.47%）显著提高、无滞后效应。除此之外，我们通过构筑低维Ruddlesden-Popper（RP）相的钙钛矿，系统的研究了其结晶动力学过程，制备了铅基和锡基钙钛矿，表现出极好的器件效率和稳定性。同时，我们发现了新型离子液体溶剂制备高效稳定钙钛矿电池的方法，摒弃了传统的溶剂，获得了效率超过20%且稳定性提升的钙钛矿太阳能电池。