Medium-vacuum thermal evaporation of CdS:O thin films towards industrial CdS/CdTe solar cells: Temperature and O2% optimization

Oxygenated CdS thin films were deposited on Fluorine-doped Tin Oxide glasses by thermal evaporation technique at medium vacuum. The substrate temperature, source temperature and oxygen concentration at the ambient were varied to obtain optimum characteristics. The post-heat-treated thin films were subjected to optical, morphological and structural characterizations to achieve optimum deposition conditions. The optical bandgaps of this study were varied within 2.41–2.47 eV, and the highest average bandgap value of 2.47 eV was obtained from the CdS layer deposited at the substrate temperature of 150 °C, source temperature of 500 °C and 20% oxygen ambient. Crystallite size, microstrain and lattice parameters were obtained using XRD line profile analysis and the Pawley refinement technique. CdS/CdTe/Cu/Au solar cells were fabricated, and the highest average efficiency of 8.32% was observed from the CdS layers deposited with the above conditions.