Coordination Chemistry Dictates the Structural Defects in Lead Halide Perovskites

Abstract We show the influence of species present in precursor solution during formation of lead halide perovskite materials on the structural defects of the films. The coordination of lead by competing solvent molecules and iodide ions dictate the type of complexes present in the films. Depending on the processing conditions all PbIS 5 + , PbI 2 S 4, PbI 3 S 3 − , PbI 4 S 2 2− , PbI 5 S 2 3− , PbI 6 4− and 1D (Pb 2 I 4 ) n chains are observed by absorption measurements. Different parameters are studied such as polarity of the solvent, concentration of iodide ions, concentration of solvent molecules and temperature. It is concluded that strongly coordinating solvents will preferentially form species with a low number of iodide ions and less coordinative solvents generate high concentration of PbI 6 − . We furthermore propose that all these plumbate ions may act as structural defects determining electronic properties of the photovoltaic films.