Phase-Pure α-FAPbI<sub>3</sub> for Perovskite Solar Cells
Tingting Niu, Lingfeng Chao, Dong Xue, Li Fu, Yonghua Chen
Abstract
Because of the narrow bandgap and superior thermal stability, FAPbI3 is considered the most promising perovskite material for high-performance single-junction PSCs. Nevertheless, the metastable properties of the photoactive α-FAPbI3 becomes a primary obstacle for the development of FA-based PSCs. The main reasons for the instability of α-FAPbI3 are the rotation disorder of the FA cation and large anisotropic lattice strain, which lead to the high formation energy of α-FAPbI3. In this Perspective, we review various strategies for preparing phase-pure α-FAPbI3, such as engineering, intermediate phase engineering, and dimensionality engineering. These strategies can stabilize α-FAPbI3 by reducing the system energy, regulating the phase transition process and energy barrier, reinforcing the lattice structure, and passivating film defects. In addition, we investigate fundamental challenges of α-FAPbI3 PSCs and propose our perspective on preparing high-quality and high-purity α-FAPbI3.