Electrosynthesis of oxide films on flexible plastics

Abstract

Transparent zinc oxide (ZnO) films on flexible copper-coated polyethylene terephthalate (PET) sheet have been grown by a potentiostatic cathodic deposition technique using aqueous zinc nitrate as the electrolyte. In this project, different deposition parameters such as applied cathodic potential, concentration of electrolyte and bath temperature had been used to fabricate the ZnO films. Their structural and optical properties were characterized by X-ray diffractometer (XRD), scanning electron microscope (SEM), diffuse reflectance UV-VIS spectrophotometer and photoluminescence (PL) spectrometer. On the basis of our measurements, the effects of different deposition parameters on the structural and optical properties of the ZnO films have been revealed. Furthermore, we demonstrated that high quality ZnO films have been successfully grown on flexible polymeric substrates using a low temperature potentiostatic cathodic deposition technique. Apart from ZnO films, cuprous oxide (Cu₂O) films were depositedon flexible copper-coated PET substrates using potentiostatic cathodic deposition technique. The electrolyte used in fabricating the Cu₂O films was a mixture of copper(II) sulphate, lactic acid and sodium hydroxide. Similar to ZnO films, the effects of processing parameters such as applied cathodic potential and deposition time on the structural, electraical and optical properties of the deposited Cu₂O films were investigated. Well-defined polycrystalline Cu₂O was electrodeposited on metalized PET substrates. Finally, experimental conditions, for example, deposition voltage and temperature of the deposition solution were especially important in controlling the morphology of the deposited ZnO on Cu₂O film. In this thesis, a mechanism for the deposition process has been proposed based on our experimental results. Based on the optimal processing parameters for ZnO as well as Cu₂O films, heterojunctions of ZnO/Cu₂O on Cu-coated PET structure were fabricated. Their electrical properties were measured. The photovoltaic properties of the ZnO/Cu₂O heterostructure were demonstrated by our electrical measurements. XRD and SEM were employed to characterize the structure and surface morphology of the Cu₂O films respectively. The optical absorption was measured by a transmission UV-VIS spectrometer.