Formamidinium Haloplumbate Intermediates: The Missing Link in a Chain of Hybrid Perovskites Crystallization

A complete screening of compositions of crystallizing products of hybrid perovskites in the most popular dimethylformamide (DMF)/dimethyl sulfoxide (DMSO) solvents is performed for various cations (FA+/MA+) and anions (I–/Br–). We found four new solvate phases of formamidinium hybrid perovskites, (FA)2Pb3I8·4DMF, FAPbI3·2DMF, (FA)5Pb2I9·0.5DMSO, and even the bromide solvate (FA)2PbBr4·DMSO. These compounds are observed for the first time, and their refined crystal structures showed large cells of unique types dependent on solvent and perovskite compositions. We also monitored crystallization pathways of multicompositional thin films and identified phases that are able to crystallize from mixed cation and anion solutions. Based on the obtained data, we performed a deep analysis of the structural peculiarities of all the solvate phases observed in the screened compositional space and discussed how the solution composition would predetermine the early stages of crystallization of target perovskite films.