Efficient and Stable β-CsPbI<sub>3</sub>Solar Cells through Solvent Engineering with Methylamine Acetate Ionic Liquid
Yifan Lv, Yiqun Li, Yan Zhou, Jin Liu, Jinpei Wang, Yuexin Lin, Jianfei Hu, Tengfei Pan, Yajing Li, Kaiyu Wang, Yingdong Xia, Wei Shi, Yonghua Chen
Abstract
CsPbI 3, an all-inorganic perovskite material with suitable band gap and excellent thermal stability, has garnered significant attention for its potential in perovskite solar cells (PSCs). However, CsPbI 3 is susceptible to phase changes from photoactive to photoinactive in humid environments. Hence, it is crucial to achieve controllable growth of CsPbI 3 perovskite thin films with the desired β-crystal phase and compact morphology for efficient and stable PSCs. Herein, MAAc was used as a solvent for the CsPbI 3 precursor to fabricate β-CsPbI 3 perovskite. An intermediate compound of Cs x MA 1– x PbI x Ac 3– x was initially formed in the MAAc solution, and during annealing, the MA + and Ac – ions were replaced by Cs + and I – ions, respectively. Furthermore, the incorporation of strong C═O···Pb coordination stabilized the black-phase β-CsPbI 3 and facilitated the growth of crystals with a narrow vertical orientation and large grain size. As a result, the PSCs with an efficiency of 18.9% and improved stability (less than 10% decay after 2000 h of storage in N 2 and less than 30% decay after 500 h of storage in humid air without any encapsulation) were achieved.