Crystallization of perovskite films was performed in supercritical carbon dioxide with and without organic co-solvents. Post deposition crystallization of the films was performed in a binary, single phase supercritical fluid at constant conditions (45° C., 1200 psi) but with varying organic co-solvent volume fractions up to 2%. The co-solvents can provide selective interactions with one or both of the perovskite precursor compounds resulting in different film morphologies ranging from uniform films containing large grains to films exhibiting large cubic or hexagonal crystals or preferential crystallographic orientations. The use of supercritical fluids to enhance or tune crystallization in solid-state thin films could have broad applications toward the realization of high efficiency photovoltaic devices.