Preparation,properties And Photovoltaic Implication Of PolycrystallineCd_1-xZn_xTe Thin Films

Photovoltaic solar energy conversion is one of the important ways to resolve the global energy crisis and environment pollution. The intention of this paper is to study the deposition of polycrystalline Cd1-xZnxTe thin films and to make a proper Cd1-xZnxTe thin film as a buffer layer of CdS/CdTe/ZnTe:Cu solar cell in order to improve the performance of the cells.A series of Cd1-xZnxTe thin films of varied compositions have been prepared by simultaneous evaporation. The films' cubic phase is demonstrated by XRD before and after annealing. The film surface appearance is characterized as uniformed and without phis by AFM. Cd1-xZnxTe thin films are testified of p-type conductivity by electromotive forces with difference in temperature. Predominant direct optical transitions have been observed and the optical energy gap varies with zinc content in a quadratic way.The original intention of using a polycrystalline Cd1-xZnxTe thin film as a buffer layer is to modify the energy band diagram of CdS/CdTe/ZnTe:Cu solar cell. There is a 1.1 ev barrier between the conduction band of CdTe and the conduction band of ZnTerCu. When introducing a buffer layer of Cd1-xZnxTe with proper band gap between the CdTe layer and the ZnTerCu layer, the 1.1ev barrier becomes two small barriers, which will improve the performance of solar cells.CdS/ CdTe/ZnTe:Cu solar cells and CdS/CdTe /Cd0.4Zn0.6Te /ZnTe:Cu solar cells have been fabricated in the same conditions, and we find the average conversion efficiency of the latter is unproved by 35% than the former.The work is an introductory step of the program "Studies of polycrystalline CdS/CdTe solar cells with new structures" supported by The Nation Natural Science Funds of China. It is also a part of the program "Explorations and studies of polycrystalline film materials and solar cells" in "The fundamental studies of solar cells with low prices, long lives and new types" supported by 973 Program of China. The main ideals and results of this paper have not been found in previous reports, and will be valuable to improve the efficiency of CdTe solar cells.