Enhancing Efficiency of Dye-Sensitized Solar Cells Using TiO2 Composite Films and RF-Sputtered Passivating Layer

Abstract

The aim of this work is to prevent the backtransfer of electrons due to direct contact between the electrolyte and the conductive substrate by using TiO2 passivation. A thin TiO2 passivating layer was deposited on a fluorine-doped tin oxide (FTO) glass by radio frequency (RF) magnetron sputtering at different RF powers and substrate temperatures. A nanoporous TiO2 nanoparticles/TiO2 nanotubes (TNTs) upper layer was deposited by the screen-printing method on the TiO2 passivating layer. The crystal structure and the morphology were characterized by X-ray diffraction (XRD) and a scanning electron microscope (SEM). The transmittance of TiO2 films were characterized by ultraviolet–visible spectroscopy (UV-Vis). The conversion efficiency of a dye-sensitized solar cell (DSSC) was measured by a solar simulator (100 mW cm−2). The thickness and the crystalline structure were adjusted by applying various working conditions, and the optical transmittance of the TiO2 films depended on the morphology of the TiO2 passivating layer. Using a TiO2 passivating layer and a TiO2/TNT hybrid electrode, the maximum conversion efficiency of the DSSC was measured to be 5.12%, due to the effective prevention of electron recombination to electrolyte. It was also found that the conversion efficiency of the DSSC was highly affected by the crystalline structure and thickness of the passivating layer.