Observation of mixed types of energy gaps in some II–VI semiconductors nanostructured films. Towards enhanced solar cell performance

All solid-state quantum dots embedded multi-junction solar cell with the device structure of (Glass/ITO/ZnTe/ZnS/CdS/Au) is achieved to boost the photo-conversion efficiency by incorporating inner layer of ZnS and by effectively utilizing the entire solar spectrum. Electron beam evaporation was used to deposit the three semiconductor materials ZnTe, ZnS and CdS thin films. The optical properties and energy bandgap of each of the three materials were determined using ellipsometric measurements. The device performance was investigated using current voltage (J–V) techniques at room temperature and under AM1.5 illumination conditions. In this study, we showed that the optical energy gaps of some nanoscale binary semiconductor compounds from II–VI family exhibit both direct and indirect types of optical energy bandgap and there is a giant increase in their direct values.