This thesis describes the development and characterization of single crystal and polycrystalline CdTe/ZnxCd1-xS based solar cells along with the modeling of CdTe based solar cells. Solar cells hold great hopes for use as an environmental friendly and economically viable renewable energy source. For this purpose thin film materials are being investigated by various research organizations and groups. In this work we have developed ZnxCd1-xS thin film as window layer, CdTe as absorber and ZnTe thin film to solve the back contact problem of CdTe (due to high work function) and studied their optical, electrical and structural properties. The polycrystalline layers of ZnxCd1-xS, ZnTe and CdTe solar cell in both “Superstrate” and “Substrate” configurations were developed. I-V characterization for single crystal CdTe based solar cells at different illumination levels and temperatures were carried out, which showed 14.37% efficiency. We have applied 1-D modeling to these cells to improve the efficiency at lower illumination levels. All thin film ZnxCd1-xS/CdTe solar cell showed low efficiency (1.7%) which was improved up to 3.7% by annealing the cell at 200oC for three hours.