PROPERTIES OF ELECTROCHEMICALLY DEPOSITED CDTE THIN FILMS

Abstract: Thin films of CdTe have been deposited on to stainless steel and fluorine doped tin oxide (FTO) coated glass substrates from aqueous acidic bath using electro deposition technique. The different preparative parameters, such as deposition time, bath temperature, pH of the bath have been optimized by photo electrochemical (PEC) technique in order to get good quality photosensitive material. The deposited films are annealed at different temperature in presence of air. Annealing temperature is also optimized by photo electrochemical (PEC) technique. The film annealed at 200OC showed more photosensitivity. Different techniques have been used to characterize the as deposited and annealed (at 200OC) CdTe thin film. The X-ray diffraction (XRD) analysis showed the polycrystalline nature and a significant increase in the XRD peak intensities is observed for the CdTe films after annealing. Optical absorption shows the presence of direct transition with band gap energy 1.64 eV and after annealing it decreases to 1.50 eV. Energy dispersive analysis by X-ray (EDAX) study for the as-deposited and annealed films showed nearly stoichiometric compound formation. Scanning electron microscopy (SEM) reveals that spherically shaped grains are more uniformly distributed over the surface of the substrate for the annealed CdTe film. Photovoltaic output characteristics and spectral response of the annealed film have been carried. The fill factor (ff) and power conversion efficiency (?) of the cell are found to be 71 % and 3.89 %.

Keywords: PEC, XRD, band gap, EDAX, fill factor and efficiency.