Study of CdS/AZO/FTO, CdS/FTO and CdS Thin Films Deposited by Modified Double Layer Thermal Evaporation

K.M.A. Hussain; M.S.S. Chowdhury; T. Faruqe

Abstract

The CdS/AZO/FTO, CdS/FTO and CdS thin films were deposited by a modified double-layer vacuum evaporation technique. The 90 nm of double-layer CdS thin films were prepared with the bottom layer 50 nm thick and the upper one was 40 nm thick and respective substrate temperatures were 100oC and 70oC. The physical properties of thus prepared films were characterized using X-ray diffraction (XRD), UV-VIS-NIR spectrophotometer, Hall Effect Measurement System and Scanning Electron Microscopy (SEM). The XRD study revealed that the films were polycrystalline structure and the CdS/AZO/FTO glass structures showed more crystalline plane and grain sizes are estimated at about 20 to 40 nm. The transmittance and reflectance wave spectra of those films showed optimum absorption coefficient ~106/cm and band gap values between 2.36 eV and 2.4 eV. These thin films with double layer deposition technique showed higher conductivity (~23.8 /Ω-cm), higher mobility (~81.87 cm2/Vs) and higher carrier concentration (~41 x 1017 cm-3). The transport properties of the CdS thin films might be helpful to ameliorate the efficiency of CdTe thin-film solar cells.Keywords: Carrier concentration, CdS, conductivity, modified double-layer thermal evaporation, thin film