Characteristics of indium zinc oxide thin films prepared by direct current magnetron sputtering for flexible solar cells

The In2O3–ZnO (IZO) thin films were prepared on polyethylene terephthalate substrate at room temperature by direct current (dc) magnetron sputtering. The properties of IZO thin films were studied in terms of O2 concentration and deposition parameters. As the O2 concentration in O2/Ar gas increased, the transmittances of the films were increased up to 90% and the resistivities were decreased. The systematic variation of process parameters including dc power, gas pressure and target-to-substrate distance was performed to examine the properties of the deposited films. It was disclosed that there was an optimum O2 concentration for high transmittance and low resistivity. With decrease in dc power and gas pressure and increase in target-to-substrate distance, the IZO films with high transmittance and low resistivity were obtained. The observation of the IZO films by atomic force microscopy indicated that the microstructure and surface morphology of the films were responsible for the transmittance. It was demonstrated that IZO films with a resistivity of 5.1×10−4 Ω cm and an optical transmission of 90% in the visible spectrum could be prepared at room temperature on flexible substrates.