Systems and methods are provided for fabricating pyrite thin films from molecular inks. A process is provided that comprises dissolving simple iron-bearing and sulfur-bearing molecules in an appropriate solvent and then depositing the solution onto an appropriate substrate using one of several methods (roll-to-roll coating, spraying, spin coating, etc.), resulting in a solid film consisting of the molecules. These molecular precursor films are then heated to 200-600° C. in the presence of sulfur-bearing gases (e.g., S2, H2S) to convert the molecular films into films of crystalline iron pyrite (FeS2).