Microstructured ZnO photoelectrode grown on the sputter-deposited ZnO passivating-layer for improving the photovoltaic performances

The aim of this work is to improve the photovoltaic performance of dye-sensitized solar cell (DSC) using a thin ZnO passivating-layer and micro-disc/ring structured ZnO photoelectrodes. A thin ZnO passivating-layer is prepared on the SnO2:F (FTO) substrate by facing-target sputtering technique, which prevents the short-circuit in DSC, and back-transfer of electron due to the direct-contact between the electrolyte, and the FTO substrate. Microstructured ZnO photoelectrodes are successfully grown on thin ZnO passivating-layer by a simple sol–gel process without and with 0.5, 1.0, 1.5, 2.0 g of polyethylene glycol (PEG) contents. The micro-disc/ring structured ZnO films have confirmed by field-emission secondary electron and atomic force microscopes. The DSC has assembled using ruthenium-based dye, microstructured ZnO films, KI/I2-based electrolyte, and carbon counter-electrode. The photovoltage and the fill factor of DSCs have improved due to the presence of the ZnO passivating-layer. The photocurrent, photovoltage, and the photoelectric conversion efficiency of DSC increase with the increase of PEG contents. The DSC based on ZnO films prepared with 2.0 g of PEG shows the maximum efficiency of 1.83%, photovoltage of 463 mV, and photocurrent of 7.2 mA cm−2 in 100 mW cm−2 light intensity.