Low temperature co-evaporation of hollow CsPbI3 perovskite layers for solar cells

The structure stability and optoelectronic properties of co-evaporated CsPbI3 thin films with a wide range of [CsI]/[PbI2] compositional ratios are investigated. We find that for CsI-rich growth conditions, CsPbI3 can be synthesized directly at low temperature into the distorted perovskite  CsPbI3 phase with Schottky-type defects and without detectable secondary phases. In contrast, PbI2-rich growth conditions are found to lead to the non-perovskite phase. Photoluminescence spectroscopy and optical pump-THz probe measurements show carrier lifetimes larger than 75 ns and charge carrier (sum) mobilities larger 60 cm/Vs for the -phase, indicating their suitability for high efficiency solar cells. Building on these results pi-n type solar cells with a maximum efficiency exceeding 12 % and high shelf stability of more than 1200 h are demonstrated.