Homogeneous FACsPbI 3 Films via Sequential Deposition for Efficient and Stable Perovskite Solar Cells

作者：Xiongzhuo Jiang, Jie Zeng, Kun Sun, Zerui Li, Guangjiu Pan, Renjun Guo, Matthias Schwartzkopf, Stephan V. Roth, Baomin Xu, Peter Müller‐Buschbaum · 发表于：Advanced Science · 年份：2025 · DOI：10.1002/advs.202506234 · 被引用次数：12 · 研究领域：Perovskite Materials and Applications、Solid-state spectroscopy and crystallography、Quantum Dots Synthesis And Properties

Abstract Despite significant advancements in the power conversion efficiency (PCE) of FAPbI 3 ‐based perovskite solar cells (PSCs), their commercialization remains hindered by stability issues. These challenges arise primarily from the phase transition of the α‐phase to the δ‐phase under operation. Alloying FAPbI 3 with Cs to form FA‐Cs perovskite (FACsPbI 3 ) emerged as a promising approach to enhance phase and thermal stability. In this study, it is demonstrated that adding a Cs source to the PbI 2 solution promotes the formation of a structurally stable α‐phase in the PbI 2 film. This stabilization reduces cation diffusion but leads to Cs accumulation at the surface of the perovskite layer. To address this issue, a δ‐phase perovskite in the PbI 2 film by predepositing the Cs source before PbI 2 deposition is constructed. This approach facilitates the uniform vertical distribution of FA and Cs cations, resulting in a homogeneous perovskite (h‐perovskite) device. The h‐perovskite device achieves a higher PCE of 24.59%, compared to 22.96% for the inhomogeneous perovskite (i‐perovskite) device. Operando GIWAXS measurements reveal that the h‐perovskite exhibits a slower degradation rate than the i‐perovskite during device operation. This difference is attributed to the formation of the δ‐phase and a stronger crystal lattice contraction observed in the i‐perovskite during the operando measurements.