Sulphurization temperature effect on suppressing CuS phase in kesterite CZTS films grown by electrodeposition method

In this study, kesterite Cu2ZnSnS4 thin films were deposited on indium tin oxide substrates by co-electrodeposition method followed with sulphurization at different temperatures. The deposited films are characterized by X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), Fourier transform infrared and UV–visible spectroscopy. XRD analysis reveals that the films crystallinity is highly influenced by sulphurization temperature, and a temperature of 550°C was sufficient to remove the CuS secondary phase. Moreover, the film sulphurized at 550°C exhibits the lowest lattice strain, the minimal number of crystallites and the highest crystallite size (98.3 nm). However, the films sulphurized at temperature lower than 550°C is composed of kesterite CZTS with CuS as secondary phase. According to the Raman spectroscopy measurments, all films spectra exhibit the intense characteristic line of the CZTS (332 cm–1) assigned to the A symmetry mode. The SEM images reveal that the surface morphology of the films became smooth and void-free as the sulphurization temperature increases. The film sulphurized at 550°C had a suitable bandgap of 1.47 eV, very close to the characteristic values for the pure kesterite CZTS.