Design of High-Efficiency and Environmentally Stable Mixed-Dimensional Perovskite Solar Cells Based on Cesium-Formamidinium Lead Halide Component

Long-term instability of the high-efficiency perovskite solar cells (PSCs) has been the intractable hindrance for their further commercialized applications. Here, we successfully introduced 2-hydroxyethylamine cation (HEA+) into Cs/FA mix-cations three-dimensional (3D) perovskite to form new-type stable mixed-dimensional (MD) perovskite structure based on the general formula of (HEA)2(Cs0.1FA0.9)n-1PbnI3n+1. FAPbBr3 component was also employed to improve the quality of thin films. The designed MD perovskite films exhibit better crystallization, outstanding optical properties and uniform morphology with less grain boundaries. Especially, due to inheriting the advantages of high-performance FA-based 3D perovskite, the PSCs made from MD-Br10 (n=30) perovskite achieve the optimal power conversion efficiency (PCE) as high as 19.84% and an average PCE of 19.02% among 30 devices. Surprisingly, it is found that the MD PSCs show superior long-term stability when exposed to heat and moisture, attributing to the hig...