Structural and optical properties of thermally treated CdO thin films deposited on ITO coated glass substrates for photovoltaic applications

In this study, we have reported effects of post-deposition thermal treatment of cadmium oxide thin films on indium tin oxide coated glass substrates by sol–gel technique using spin coating method. To prepare CdO thin films, a precursor solution based on a derivative from cadmium acetate was gelated and subsequently coated on ITO/glass substrates. Spin coated CdO films were annealed in air at varied temperatures of 300, 400, and 500 °C. The crystallite size, microstrain and dislocation density were estimated from high resolution X-ray diffraction analysis. X-ray diffraction patterns confirmed cubic phase formation in polycrystalline CdO films. Cross-sectional and top surface morphology of the films was studied by field-enhanced scanning electron microscopy. The as-deposited and thermally treated CdO thin films for various annealing temperatures showed an increase in the optical transmittance to 79% from that of 63% of CdO film in the visible and near infrared region. Shrinkage in band gap from 2.6 to 2.4 eV was reported for temperature variation of 300–500 °C. The emission properties of as-deposited and thermally treated CdO thin films were studied by photoluminescence spectrum recorded at 298 K.