The impact of highly excessive PbI2 on the correlation of MAPbI3 perovskite morphology and carrier lifetimes

Abstract

The morphology of methylammonium lead iodide MAPbI₃, formed by a two-step method with non-stoichiometric, excessive PbI₂ concentration for a high carrier lifetime is reported. Through this excessive PbI₂ alteration, the morphology, crystallinity, and carrier lifetime are purposely optimized. When the PbI₂ concentration was 0.5 g ml⁻¹, the nanotubes started to appear and were mixed with perovskite thin film, which yielded a significant average value of an effective carrier lifetime of 14.1 μs, resulting from the microwave photoconductivity decay on the perovskite prepared from the optimized method. The local value of effective carrier lifetime even reached above 60 μs at several locations. When the PbI₂ concentration reached 0.6 g ml⁻¹, synthetic perovskites contained bundles of nanotubes. This study provides a new framework for optimizing perovskites with appropriate surplus PbI₂ and offers a scalable pathway for fabricating the perovskite material for best solar conversion efficiency.