Lu Linyang, Shen Kong-Chao, Wang Jingkun, Su Zhenhuang, Li Yanqing, Chen Li, Luo Yuxin, Song Fei, Gao Xingyu, Tang Jian-Xin
Jiangsu Key Laboratory for Carbon-Based Functional Materials and Devices, Institute of Functional Nano and Soft Materials (FUNSOM), Soochow University, Suzhou, Jiangsu 215123, P. R. China.
Key Laboratory of Interfacial Physics and Technology, Shanghai Institute of Applied Physics, and Shanghai Synchrotron Radiation Facility, Zhangjiang Laboratory, Chinese Academy of Sciences, Shanghai 201204, China.
ACS Appl Mater Interfaces. 2020 Sep 16;12(37):42369-42377. doi: 10.1021/acsami.0c11696. Epub 2020 Sep 4.
Mixed A-site engineering is an emerging strategy to overcome the difficulties in realizing high-quality perovskite films together with high ambient stability. Particularly, the α-FACsPbI-based hybrid perovskites have been considered as a promising candidate for solar cell applications. However, the degradation mechanism of α-FACsPbI hybrid perovskites induced by light illumination remains unclear. Here, the illumination-caused instability of α-FACsPbI hybrid perovskites is investigated using various surface detection technologies, including photoelectron spectroscopy, scanning electron microscopy, and grazing incidence X-ray diffraction. The experimental findings reveal that the A-site vacancies arise from the migration of Cs cations from the perovskite surface into the bulk under light illumination, while their content is dependent on the light energy. The visible light enlarges the crystal lattice on the perovskite surface, leading to the Cs cation migration along with the lattice distortion of the PbI octahedron and phase separation. However, the ultraviolet light further causes a stronger interaction between FA and [PbI], leading to the partial decomposition of [PbI] into Pb and I. These results enrich the photodegradation mechanism, guiding the design of efficient and stable perovskite solar cells through surface passivation to suppress the Cs cation migration and to increase the octahedron dissociation energy.
混合A位工程是一种新兴策略，用于克服在实现高质量钙钛矿薄膜以及高环境稳定性方面所面临的困难。特别是，基于α-FACsPbI的混合钙钛矿被认为是太阳能电池应用的一个有前途的候选材料。然而，光照诱导的α-FACsPbI混合钙钛矿的降解机制仍不清楚。在此，利用各种表面检测技术，包括光电子能谱、扫描电子显微镜和掠入射X射线衍射，研究了α-FACsPbI混合钙钛矿光照引起的不稳定性。实验结果表明，A位空位是由光照下Cs阳离子从钙钛矿表面迁移到体相中产生的，而其含量取决于光能。可见光扩大了钙钛矿表面的晶格，导致Cs阳离子迁移以及PbI八面体的晶格畸变和相分离。然而，紫外光进一步导致FA与[PbI]之间更强的相互作用，导致[PbI]部分分解为Pb和I。这些结果丰富了光降解机制，通过表面钝化来抑制Cs阳离子迁移并提高八面体解离能，从而指导高效稳定的钙钛矿太阳能电池的设计。
