Hansen theory applied to the identification of nonhazardous solvents for hybrid perovskite thin-films processing

Metal-halide perovskites have become the most studied material for efficient next-generation solar cells, in part because of the possibility of depositing high quality semiconducting perovskites by simple solution-based methods. However, the majority of solvent systems implemented in literature for deposition of lead halide perovskites are hazardous to handle. Investigation of alternatives perovskite processing methods are hence key to safely upscale the perovskite photovoltaic manufacturing. In this manuscript we use the Hansen theory to find suitable nonhazardous solvents to solubilize two lead salts, PbBr2 and PbI2, used to fabricate the corresponding methylammonium (MA) lead halide perovskite films. The method is based on the use of the Hansen solubility parameters (HSPs) of a lead salt and a solvent to provide insight into whether interactions between them are favorable or not. We first studied the solubility properties of each lead salt (PbBr2 and PbI2) by determining experimentally their Hansen solubility spheres. Using these results, computer simulations allow us to determine compatible nonhazardous solvents with these two compounds in terms of solubility. We further investigated the use of a nonhazardous diester blend polar solvent to deposit MAPbI3 and MAPbBr3 thin films.