Physico-chemical studies of Cd1−xZnxS thin films produced by simple two-electrode electrodeposition system for solar cell application

Abstract

Cd1−xZnxS thin films have been cathodically electrodeposited on glass/fluorine-doped tin oxide substrates using a low-cost two-electrode configuration with an electrolytic bath containing cadmium chloride, zinc chloride and sodium thiosulphate precursors. The deposition was carried out by varying zinc chloride concentration (0 M, 0.3 M, 0.6 M and 0.9 M) in the deposition electrolyte. The structural, compositional, phonon vibrational, morphological and optical properties of the resulting films have been characterized using glancing incidence X-ray diffraction, energy-dispersive X-ray (EDX) spectroscopy, Raman spectroscopy, scanning electron microscopy (SEM) and UV–Vis spectrophotometry respectively. The XRD result indicates the existence of hexagonal structure of Cd1−xZnxS with intensities of the diffraction peaks decreasing as more Zn is incorporated into the film as a result of decrease in deposition rate. EDX results show the presence of Cd, Zn and S in the deposited Cd1−xZnxS thin films. SEM images show uniform and densely packed surface morphology of the films with distinct shaped grains which gradually less distinct as more Zn is incorporated into the films. The optical measurements reveal a significant increase in energy band gap of the Cd1−xZnxS material as more zinc is incorporated into the films and a film thickness decreases with the energy band gap increasing from 2.40 eV for CdS to 2.62 eV for Cd1−xZnxS. These results show that Cd1−xZnxS material can be applied as a better window material for CdTe, CIG(S,Se) and CZTS-based solar cells than CdS.