Production and characterizaton of SnO2:Cu/CdS films for solar cell applications

In this thesis, the production and characterization of SnO2:Cu/CdS films which can be used for solar cell applications were carried out. SnO2:Cu/CdS films were produced on glass substrates using chemical spraying technique. First of all, SnO2, CdS, SnO2:Cu films were produced as separate layers, and finally SnO2:Cu/CdS heterojunction films were obtained. Structural, optical, electrical and surface properties of the produced films were investigated to determine the solar cell usage potential. It was determined that the films were polycrystalline in tetragonal structure. The preferred orientation of the CdS along (002) direction at 2θ = 26.60º. The other peaks were detected at 2θ = 44 and 52º which can be ascribed due to reflection from (110), and (112) planes of the hexagonal CdS structure. Atomic force microcope (AFM) results shows that the distribution of grains on the surface is almost uniform and homogeneous, and the film is without any cracks. The results showed that the average surface roughness of the SnO2, CdS and SnO2:Cu/CdS films were 10.7 nm, 17.6 nm and 18.8 nm, respectively. A Scanning Electron Microscope (SEM) results shows that the surfaces of the prepared films have spherical particles, with a homogeneous distribution on the substrate, and there are no cracks on the surface of the film or large molecular agglomerations. Energy-dispersive X-ray spectroscopy (EDX) results shows that the the elements that formed the film (SnO2) which are tin (Sn), chlorine (Cl), oxygen (O), and silicon (Si). UV-VIS spectrophotometer was used to determine the optical parameters of the films such as transmittance, absorption, band gap and refractive index. The average transmittance and band gap values of the films in the visible region were found to be 70 % and 3.75 eV, respectively. The calculated energy gap values for SnO2, SnO2:Cu, SnO2:Cu/CdS, and CdS films were 3.90, 3.88, 3.75 and 2.28 eV respectively. With the temperature-dependent conductivity measurement, it was observed that the films had n-type conductivity. Besides, the resistivity values of the films decreased with Cu doping and the SnO2:Cu/CdS films had low resistivity (3.25×10-3 Ωcm). The surface properties and elemental analyses of the films were examined using atomic force microscopy and scanning electron microscopy, and it was seen that they had a homogeneous surface morphology.