Effect of sulfur concentration on structural, optical and electrical properties of Cu2CoSnS4 absorber film for photovoltaic devices

In this study, Cu2CoSnS4 (CCTS) films were grown on glass substrates by dipping the sol-gel method. The effect of the thiourea molarity in solution on film properties was investigated. X-ray diffraction (XRD) and Raman Scattering were used to determine the structure of the prepared films. Raman spectroscopic results showed that films with low thiourea molarity have two phases, Cu2-xS and Cu2CoSnS4. As the thiourea molarity increases, this Cu2-xS phase disappears. Optical band gap values found with the help of optical transmittance measurements of the films also decreased from 1.7eV to 1.4eV with increasing thiourea molarity. Morphological properties were examined by Scanning Electron Microscope (SEM) and Atomic Force Microscopy (AFM). The electrical resistivity of the prepared films is also studied by the two-contact method at room temperature. In general, structural, optical, morphological, and electrical properties of the films were affected by thiourea molarity in solution.