A novel synthesis of the bottom-straight and top-bent dual TiO2 nanowires for dye-sensitized solar cells

Abstract

The bottom-straight and top-bent dual anatase TiO2 nanowires directly on flurine-doped tin oxide (FTO) glass substrate are successfully synthesized for the first time via a two-step solvothermal reaction, which obtains single anatase TiO2 nanowires with the diameter of 250–450 nm and the length of ∼49 μm in the first growth step, and the slender TiO2 nanowires with the diameter of 40–80 nm intertwining larger nanowires to form dual nanowires network in the secondary growth step. Dye-sensitized solar cell (DSSC) based on dual TiO2 nanowires exhibits the power conversion efficiency of 5.30%, which is much higher than those of DSSCs based on the pristine single TiO2 nanwires (2.36%) due to the twining network like dual nanowires structure maintaining excellent electron transport and simultaneously enhancing the specific surface area and light scattering ability. Moreover, by TiO2 sol treatment, the performance of dual TiO2 nanowires based DSSC can be further enhanced, reaching an impressive power conversion efficiency (PCE) of 7.65%.