Correlation between soft annealing conditions and structural, microstructural, morphological, and optical properties of CuInS2 thin films prepared by sulfurization of stacked precursor

• CIS thin films were synthesized by sulfurization of In/Cu metallic precursor.
• Effects of S vaporization temperatures on the properties of CIS thin films were investigated.
• The low cost and high PCE of TFSCs can be fabricated using CIS absorber layer.

CuInS2 (CIS) thin films were prepared by sulfurization of In/Cu stacked precursor films. Prior to sulfurization the stacked metallic precursors were subjected to the soft annealing in Ar atmosphere at different time (10, 30, and 60 min) and temperature (100 °C and 300 °C). The effect of soft annealing condition on the structural, morphological and optical properties of CIS films was investigated. X-ray diffraction, Raman, and X-ray photoelectron spectroscopy studies showed that the sulfurized thin films exhibited a CIS tetragonal structure with minor secondary phases such as Cu2−xS and CuIn5S8. The secondary phases were minimized by introducing soft annealed process in the CIS thin films. Void free CIS microstructures have been observed for soft annealed CIS films. The band gap energy of CIS films were increased from 1.37 to 1.5 eV depending on the soft annealing conditions.