Effects of heat treatment of vacuum evaporated CdCl2 layer on the properties of CdS/CdTe solar cells

In this work, CdTe films were prepared by r.f. magnetron sputtering. Influence of dry CdCl2 treatments on the structural and optical properties of CdTe films was investigated by field emission scanning electron microscope (FE-SEM), X-ray diffraction (XRD), and UV–Visible spectrophotometer. Also, CdS/CdTe thin film solar cells were fabricated by all sputtering process and the cell characteristics were studied. The as-deposited CdTe thin films had a zincblende structure highly oriented with the (111) direction parallel to the substrate surface. The CdTe films lose their preferred orientation and become polycrystalline by heat treatment with dry CdCl2 treatment. The wet CdCl2 treatment exhibited a similar trend, but is less effective for grain growth than dry CdCl2 treatment. The photovoltaic properties of the CdS/CdTe solar cell were considerably improved with the increase in the annealing temperature, which was caused by the increase of grain size in CdTe films. However, the wet CdCl2 process was not suitable for reproducible fabrication.

► Influence of wet and dry CdCl2 treatments on the properties of CdTe films was investigated.
► Characteristics of CdS/CdTe solar cells fabricated by all sputtering were studied.
► The photovoltaic properties of the cell were considerably improved by CdCl2 treatment.
► However, the wet CdCl2 process was not suitable for reproducible fabrication.