Cesium acetate-assisted crystallization for high-performance inverted CsPbI₃perovskite solar cells

Efficient inverted (p-i-n) type CsPbI₃perovskite solar cells (PSCs) have revealed promising applications due to their excellent thermal and photostability. Regulating the nucleation and crystallization of perovskite film is an important route to improving the performance of CsPbI₃PSCs. Herein, we explored cesium acetate (CsAc) as additive to manipulate the crystallization process of CsPbI₃perovskite films. By involving in the intermediate phase DMA_1-CsPbI_3-Acof perovskite, the pseudo-halide acetate (Ac^-) can retard the ion exchange reaction between DMA⁺and Cs⁺, leading to a perovskite with dense morphology, low defect density, and a long carrier lifetime. As a result, the optimal CsPbI₃PSCs yielded a high power conversion efficiency of 18.3%. Moreover, the encapsulated devices showed excellent operational stability and the devices retained their initial performance following 500 h of operation at the maximum power point under one-sun illumination in ambient conditions.