Properties of ZnTe:Cu thin films and CdS/CdTe/ZnTe solar cells

The effects of Cu doping and post-deposition annealing on the properties of ZnTe thin films and CdS/CdTe solar cells with the ZnTe:Cu/Au back contact were investigated. The structural, compositional and electrical properties of ZnTe films were studied systematically using X-ray diffraction (XRD), electron microprobe analysis, atomic force microscopy (AFM), electrical resistivity and Hall effect measurements. ZnTe films with Cu concentrations of 1-6 at. % were used successfully as a back contact layer, providing fill factors over 0.70. The stability of CdTe/ZnTe/Au cells under accelerated temperature stress tests was investigated. I-V and C-V measurements, scanning Auger electron spectroscopy (AES) and X-ray photoemission spectroscopy (XPS) were used to clarify possible degradation mechanisms. Significant Cu and Te diffusion into Au layer and Au diffusion into ZnTe were observed after annealing.