Preparation of (111) Facet-Dominated Perovskite Films for Highly Efficient and Stable Perovskite Solar Cells

Most of the reported perovskite solar cells (PSCs) with high efficiency are based on the (100) facet-dominated FAPbI₃ perovskite films due to their easy formation. Recent reports demonstrate that the (111) facet is more stable and more invulnerable to cationic migration than the (100) one. However, the fabrication of (111) facet-dominated perovskite is challenging. Herein, we prepared the (111) facet-dominated perovskite films by a two-step method. In the first step, an additive of 6,6'-dimethyl-2,2'-bipyridyl (DMBP) was added to the PbI₂ solution, which interacts with PbI₂ by a chemical bonding between Pb⁺ and N^- in its pyridine rings, regulating the microstructure of the PbI₂ film. The experimental results demonstrate that the obtained perovskite film is (111) facet-dominated. Moreover, the DMBP additive reduces the number of defects and improves the energy band structure of the perovskite. The devices based on the (111) facet-dominated perovskite achieve a high efficiency of 24.11%, which is larger than that of the control (22.55%). In addition, the stability of the devices is enhanced by the DMBP additive.