Syntheses,Crystal Structures,and Optical Properties of the Hexagonal Perovskites Variants ABX3 (B = Ni,A = Gu,FA, MA,X = Cl,Br; B = Mn,A = MA,X = Br)

Herein we report on our systematic investigations on the solution processed synthesis and characterization of transition metal halides (guanidinium, formamidinium, and methylammonium nickel bromides and chlorides as well as methylammonium manganese bromide) with the composition ABX₃ (A = organic cation; B = Mn, Ni; X = Cl, Br). The investigations were carried out with respect to possible applications of 3d transition metal compounds for the perovskite solar cell. All the compounds represent different variants of the hexagonal perovskite structure (2H). Crystal structures and symmetry relations are discussed. Additionally, (CH₃NH₃)₂MnI₄, which consists of tetrahedral coordinated Mn²⁺, and the water containing compounds (CH₃NH₃)MnBr₃ · 2H₂O, which forms chains of edge sharing octahedra, as well as (CH₃NH₃)NiCl₃ · 2H₂O, which consists of dimers of octahedra, are presented. Investigations on the crystal structures are supported by vibrational and optical spectroscopy.