Electrochemical deposition and characterization of thin-film Cd1-xZnxS for solar cell application: The effect of cathodic deposition voltage

Cd1-xZnxS thin films have been grown by two-electrode electrodeposition method using an electrolytic bath containing cadmium chloride, zinc chloride and sodium thiosulphate. The deposition was carried out at three different cathodic voltages of 1695 mV, 1700 mV and 1705 mV. The characterization of the films was done using grazing incidence X-ray diffraction (GIXRD), energy-dispersive X-ray (EDX) spectroscopy, Raman spectroscopy, UV-Vis spectrophotometry, and scanning electron microscopy (SEM). From the GIXRD results, it is observed that the films have only hexagonal phase. With increase in deposition voltage the intensities of the characteristic peaks decrease because of incorporation of more Zn into the film resulting in reduced deposition rate, and therefore thinner films. A similar trend is observed in the Raman spectroscopy results. EDX results reveal that increase in deposition voltage increases the amount of zinc atoms incorporated into the Cd1-xZnxS thin film. Optical characterization shows that, as more Zn is incorporated into the film with increase in growth voltage, the energy band gap gradually increase from 2.42 eV to 2.51 eV, making the Cd1-xZnxS films more beneficial for application as window/buffer material in solar cells compared to CdS. The optical absorbance and transmittance of the Zn-incorporated films also decrease and increase, respectively as deposition voltage increases (i.e as more Zn is incorporated), to support this application. SEM images show uniform and densely packed surface morphology, with the grains becoming less distinctly shaped as more Zn is incorporated into the film with increase in deposition voltage.