Study of polycrystalline ZnTe (ZnTe:Cu) thin films for photovoltaic cells

摘要

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℃ are cubic and hexagonal. Cu_xTe are observed by XRD and XPS. DSC shows ZnTe:Cu film has a peak of decalescence at 170℃, which means that there can be a change. Therefore we assume ZnTe:Cu thin films have structure changes at 185℃ and the existence of Cu_xTe leads to the abnormal conductivity-temperature relationship. During annealing, copper diffuse from grain boundary to lattices. 1/C~2-V curves show that Cu_xTe can form tunneling junction with CdTe, which can improve the back contact.