Polycrystalline thin film solar cells based on CuInGaSe2 (CIGS) and CdTe as absorber layers have been developed with efficiencies 15% using CdS as the buffer layer. However, the usage of CdS in these devices is harmful to the environment and has the potential to cause the manufacture problems due to the toxicity of Cd . Further, the collection efficiency of these solar cells is limited due to the narrow band gap of CdS (2.42 eV). Therefore, in order to improve the collection efficiency, to enhance the feasibility of manufacturing and to avoid environmental problems, it is desirable to...