Abstract The opto-electronic properties and X-ray diffraction patterns of CuGaSe 2 thin films of various compositions were studied. The tetragonal phase was obtained at substrate temperature of 450°C. Films with resistivities in the range 10 −1 –10 6 μ cm, and optical bandgap of 1.66–1.69 eV were attainable by varying the composition through control of the evaporation rates of the elements. An all-thin-film CdS/CuGaSe 2 (1 cm 2 ) solar cell was fabricated to demonstrate the photovoltaic potential of CuGaSe 2 thin films.