A method for preparing photoactive perovskite materials. The method comprises the step of preparing a germanium halide precursor ink. Preparing a germanium halide precursor ink comprises the steps of: introducing a germanium halide into a vessel, introducing a first solvent to the vessel, and contacting the germanium halide with the first solvent to dissolve the germanium halide. The method further comprises depositing the germanium halide precursor ink onto a substrate, drying the germanium halide precursor ink to form a thin film, annealing the thin film, and rinsing the thin film with a second solvent and a salt.