Zinc sulfide (ZnS) thin films, with different thicknesses and different silver (Ag) middle layer thickness, were
prepared on glass substrates using thermal evaporation. The structural and optical properties of ZnS thin films were
characterized by X-ray diffraction and UV-VIS-NIR spectrophotometer. The X-ray diffraction analyses indicated
that ZnS films have cubic structure with (111) preferential orientation, whereas the diffraction patterns sharpen
with the increase in the film thickness. The intensities of the Ag peaks increased strongly while the intensities
of ZnS peaks decreased when the Ag layer increased to 86 nm. The optical band gap values decreased while the
refractive index increased with the increase of the film thickness and Ag layer thickness. These results show that
ZnS films are suitable for use as the buffer layer of the Cu(In, Ga)Se2 solar cells.