Syntheses, Crystal Structures, and Optical Properties of the Hexagonal Perovskites Variants ABX(3) (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 ABX(3) (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)(2)MnI4, which consists of tetrahedral coordinated Mn2+, and the water containing compounds (CH3NH3)MnBr(3)2H(2)O, which forms chains of edge sharing octahedra, as well as (CH3NH3)NiCl(3)2H(2)O, which consists of dimers of octahedra, are presented. Investigations on the crystal structures are supported by vibrational and optical spectroscopy.