Crystallization Pathways of FABr-PbBr 2 -DMF and FABr-PbBr 2 -DMSO Systems: The Comprehensive Picture of Formamidinium-Based Low-Dimensional Perovskite-Related Phases and Intermediate Solvates.

In this study, we systematically investigated the phase diversity and crystallization pathways of the FABr excessive regions of two ternary systems of FABr-PbBr 2 -DMF and FABr-PbBr 2 -DMSO (where FA + -formamidinium cations, DMF-dimethylformamide and DMSO-dimethyl sulfoxide solvents). In these systems, a new FA 3 PbBr 5 phase with a structure containing chains of vertex-connected PbBr 6 octahedra is discovered, and its crystal structure is refined. We experimentally assess fundamental information on differences in the mechanisms of crystallization process in FABr-PbBr 2 -DMF and FABr-PbBr 2 -DMSO systems and determine possible pathways of crystallization of hybrid perovskites. We show that intermediate solvate phases are not observed in the system with DMF solvent, while a number of crystalline solvates tend to form in the system with DMSO at various amounts of FABr excess.