Investigations on Cu3SnS4 thin films prepared by spray pyrolysis

Thin films of Cu3SnS4, a promising absorber material for thin film heterojunction solar cells, are deposited using spray pyrolysis technique. The films are deposited at 360 °C, 390 °C and 420 °C to study the effect of substrate temperature on the growth of these films. The thickness of the films is found to be ~ 0.6 μm. Films deposited at 420 °C are found to contain Cu3SnS4 as the dominant phase with CuS and Cu2SnS3 as the secondary phases. These films are annealed at 500 °C and 550 °C in sulfur atmosphere to improve the crystallinity and sulfur content in the films. With increase in the annealing temperature, the crystallinity is found to increase and the films annealed at 550 °C are found to be near-stoichiometric, cubic Cu3SnS4. The crystallite size is evaluated to be ~ 40 nm and the direct optical band gap of these films is found to be 1.75 eV.