A process for preparing thin Cd2SnO4 films. The process comprises the steps of RF sputter coating a Cd2SnO4 layer onto a first substrate; coating a second substrate with a CdS layer; contacting the Cd2SnO4 layer with the CdS layer in a water- and oxygen-free environment and heating the first and second substrates and the Cd2SnO4 and CdS layers to a temperature sufficient to induce crystallization of the Cd2SnO4 layer into a uniform single-phase spinel-type structure, for a time sufficient to allow full crystallization of the Cd2SnO4 layer at that temperature; cooling the first and second substrates to room temperature; and separating the first and second substrates and layers from each other. The process can be conducted at temperatures less than 600° C., allowing the use of inexpensive soda lime glass substrates.