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.

针对当前最常用的二甲基甲酰胺（DMF）/二甲基亚砜（DMSO）混合溶剂体系，我们针对不同甲脒阳离子（FA+）/甲胺阳离子（MA+）与碘离子（I–）/溴离子（Br–），完成了杂化钙钛矿结晶产物组分的全面筛选。本研究首次观测到四种全新的甲脒基杂化钙钛矿溶剂化物相：(FA)2Pb3I8·4DMF、FAPbI3·2DMF、(FA)5Pb2I9·0.5DMSO，以及溴化物类溶剂化物相(FA)2PbBr4·DMSO。上述化合物的精修晶体结构显示，其独特的大尺寸晶胞类型取决于溶剂种类与钙钛矿组分配比。此外，我们监测了多组分薄膜的结晶路径，并识别出可从混合阴阳离子溶液中结晶析出的物相。基于本研究获得的实验数据，我们对筛选得到的组分空间内所有观测到的溶剂化物相的结构特性展开了深入分析，并探讨了溶液组分如何预先决定目标钙钛矿薄膜结晶的早期阶段。