A new formation strategy of hybrid perovskites via room temperature reactive polyiodide melts

Here we introduce a new solvent-free preparation method for hybrid metal halide perovskites involving the direct reaction of metallic lead with polyiodide melts. We discovered new reactive polyiodide melts (RPMs) that can be prepared simply by adding elemental iodine to halide salts of the organic A cations of common hybrid perovskites, e.g. methylammonium iodide (MAI) and formamidinium iodide (FAI), and their corresponding bromide salts MABr and FABr. For MAI/I-2 ratios ranging from 1 : 1 to 1 : 3 they form room temperature ionic liquids containing polyiodide anions and organic counterions. We find that metallic lead can be converted within a few seconds into pure or mixed cation/anion large-grain perovskite films of high electronic quality by a reaction with the RPM. The melts can dissolve also lead derivatives, opening up a realm of opportunities for future development of self-flux growth, liquid phase epitaxy and crystallization of perovskites for solar cell applications.