Influence of the carrier concentration of CdS on the properties of dry process Cu2S-CdS solar cell

The results of experiments on junction parameters in samples where the substrate carrier concentration ranges from 3 x 10 to the 16th/cu cm to 4 x 10 to the 17th/cu cm are presented. The carrier concentration of the substrate is determined by the quantity of grown-in donor type defects. These defects are also responsible for the extent of copper diffusion into the substrate and hence for the width of the depletion region. Junctions having higher CdS carrier density exhibit more extensive copper compensation. For cells with low carrier concentrations, tunneling via recombination centers is observed because the depletion region is thin under illumination. Higher carrier densities mean higher defect densities and, at the same time, enhanced copper diffusion. The observed transport mechanism is recombination. In the dark, the depletion region is found to widen and all heterojunctions to exhibit recombination as the dominant process.