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.