Facile fabrication of perovskite layers with large grains through a solvent exchange approach

Large-grained perovskite layers with fewer defects are beneficial to minimize carrier recombination at grain boundaries, thus boosting cell performance. Here, we present a facile solvent exchange strategy (SES) to yield large-grained perovskite films with high reproducibility. Upon employing a stoichiometric PbI₂MAI:DMSO (3:2:2) precursor solution, we reduced the number of colloidal intermediates (PbI₄ ^2-) which is correlated with the nucleation of seeds, resulting in a perovskite thin layer with large grain sizes up to 2 μm. The SES prepared CH₃NH₃PbI₃ devices show significantly reduced grain boundaries corresponding to the decrease of recombination centers, which dramatically boosted the efficiency up to 17.2%.