Study of polycrystalline ZnTe (ZnTe:Cu) thin films for photovoltaic cells
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In our work, polycrystalline ZnTe and ZnTe:Cu thin films were deposited by vacuum co-evaporation technology. The conductivity–temperature relationship was measured. And the properties of films were studied by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and differential scanning calorimety (DSC). The results show that the as-deposited films are cubic and that the films annealed at 185°C are cubic and hexagonal. Cu x Te are observed by XRD and XPS. DSC shows ZnTe:Cu film has a peak of decalescence at 170°C, which means that there can be a change. Therefore we assume ZnTe:Cu thin films have structure changes at 185°C and the existence of Cu x Te leads to the abnormal conductivity–temperature relationship. During annealing, copper diffuse from grain boundary to lattices. 1/C 2-V curves show that Cu x Te can form tunneling junction with CdTe, which can improve the back contact.
KeywordsOhmic Contact ZnTe Abnormal Conductivity Back Contact Differential Scanning Calorimety
The XPS measurements were performed in the center of Analysis and Test of Sichuan University. The work has been supported by National High Technology Reaearch and Development Program (863 Program) of the Tenth Five-year plan of China under grant number 2001AA513010 and University Doctoral Point Foudation (No. 20050610024).
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