Effect of varied number of multilayers, for cadmium sulphide with bismuth-doped zinc oxide buffer layer, on optical properties

Multilayer of Cadmium Sulphide (CdS) and Bismuth-doped Zinc Oxide (ZnO:Bi) is a direct band gap material, capable of use as a window layer material for silicon solar cells. With tuneable energy band gaps (2.41-2.71 eV)the ZnO:Bi/CdS window multilayer can allow for absorption of a wider range of wavelengths. This paper presents the varied number of ZnO:Bi/CdS multilayers and its effect on the optical properties. Samples were prepared using 3-11 layers of CdS and 3 layers of ZnO:Bi. Optical and structural properties were investigated through techniques including UV-Vis, XRD and FTIR analysis. Trends in energy band gaps were visible in relation to the number of layers used. The ZnO:Bi/CdS window layer demonstrated good absorption/transmission properties that make it a potential way of improving existing solar cell technology. Due to the high transmission rates, wavelengths of light (> Energy band gap of 1.1 eV) harnessed by Si cells, would not be hindered, while absorption of high energy photons (UV-Visible) can be improved on bulk Si solar cells.