Highly conductive flat grains of cesium lead bromide perovskites via additive engineering with methylammonium bromide†

Perovskite solar cells made of inorganic cesium lead bromide (CsPbBr₃) display unusually high open-circuit potentials. Yet, their photovoltaic efficiency is still lagging behind that of iodide-based halide perovskites. In this study, a multistep solution spin coating process is used to create a CsPbBr₃ film. The CsPbBr₃ perovskite film consists of flat and rounded grains, and the photocurrent of each grain type is imbalanced. Interestingly, a significant current increase in flat grains is observed when conducting atomic force microscopy (c-AFM) at the nanoscale after the addition of methyl ammonium bromide (MABr) as an additive. The addition of MABr results in good optoelectronic quality of perovskite films with highly conductive grains and enables better charge transport and hence improved power conversion efficiency.