Preparation and characterization of Cu2SnS3 ternary semiconductor nanostructures via the spray pyrolysis technique for photovoltaic applications

Thin films of Cu2SnS3 have been deposited by the spray pyrolysis technique. Various Sn/Cu molar ratios (from 0.0 to 1.0) were applied, which allowed the study of the copper tin sulfide phase. Structural, morphological and compositional analyses have been carried out using x-ray diffraction, field emission scanning electron microscopy and energy dispersive spectroscopy. The pure CuS thin film showed the covellite phase with hexagonal crystal structure, and with increasing the Sn/Cu molar ratio, the films grown were crystallized with triclinic Cu2SnS3 ternary phase. Optical measurement analysis showed that the deposited layers have a relatively high absorption coefficient (similar to 10(5) cm(-1)) in the visible spectrum, about one order of magnitude higher than in other published reports. Also these layers presented a reduction of about 1 eV in the values of band gap from 2.57 to 1.58 eV with an increment in the Sn/Cu molar ratio from 0.0 to 1.0. The electrical properties studies showed that all these samples are p-type semiconductors and the resistivity decreases with increasing the Sn/Cu molar ratio.