Electrodeposition and characterisation of ZnTe layers for application in CdTe based multi-layer graded bandgap solar cells

Zinc Telluride (ZnTe) thin films have been deposited on glass/conducting glass substrates using low-cost aqueous electrodeposition (ED) method. The structural, optical and morphological properties of the resulting films have been characterized using X-ray diffraction (XRD), spectrophotometry and Scanning Electron Microscopy (SEM). It has been confirmed by XRD technique that the deposited layers are nano- and polycrystalline mixture for as deposited layers. Photoelectrochemical (PEC) studies revealed that the layers are p-type in electrical conduction. Optical absorption measurement has been used for the bandgap determination of the deposited layers. The bandgap of the polycrystalline ZnTe layers are in the range (2.65 – 2.75) eV for the ZnSO4 precursor, and (2.70 – 2.87) eV for the ZnCl2 precursor instead of (2.21 – 2.26) eV reported for crystalline ZnTe. This increase may be due to the quantum effect which confirmed by the absence of strong XRD peaks from these layers and/or inclusion of ZnO in the deposited layers.