Engineering Low-Temperature CsPbI <sub>3</sub> Crystallization via Synergistic Regulation Strategy for Efficient Inorganic Perovskite Solar Cells
Yuqi Cui, Rui Zhang, Chengyu Tan, Chunjie Huang, Xinru Qin, Xiangjin Du, Shiyu Jiang, Hongkun Wei, Yiming Li, Huijue Wu, Jiangjian Shi, Fubo Tian, Yanhong Luo, Dongmei Li, Qingbo Meng
Abstract
A high-temperature annealing process is beneficial for improving CsPbI 3 crystallinity but detrimental to its application in flexible and tandem devices. Regarding this challenge, we propose a synergistic regulation strategy to simultaneously enhance the crystallinity of blade-coated CsPbI 3 films and lower the phase transition temperature. Systematic investigation reveals that the CdI 2 incorporation could promote Cs + transfer and significantly reduce the CsPbI 3 phase transition temperature from 190 to 130 °C; meanwhile, Pb(SCN) 2 addition significantly improves the low-temperature-annealed CsPbI 3 crystal quality, even surpassing high-temperature-annealed perovskite films. Optimized CsPbI 3 films exhibit low defect density, weak nonradiative recombination, and high phase stability. Consequently, rigid CsPbI 3 solar cells achieve a champion power conversion efficiency (PCE) of 22.3%, while flexible CsPbI 3 devices present 18.6% PCE. Good operational photostability is also obtained with over 90% of the initial PCE retained after 500 h. This work demonstrates a universal low-temperature fabrication strategy to realize stable and high-quality black-phase CsPbI 3 perovskite films and perovskite solar cell (PSC) devices, typically suitable for flexible photovoltaics.