Influence of the size-controlled TiO2 nanotubes fabricated by low-temperature chemical synthesis on the dye-sensitized solar cell properties

Titanium dioxide nanotubes (TiO₂ NTs) with various sizes have been prepared by low-temperature chemical synthesis using commercial anatase TiO₂ particles with different crystallite size in NaOH solution and used as a photoelectrode in a dye-sensitized solar cell (DSSC). The relationship between the physicochemical properties of electrode materials and photovoltaic performance was investigated. The electrodes made from modified TiO₂ NTs showed a strong dependency on their specific surface area and resultant amount of dye adsorption; the surface area decreased with increase in the diameter of the NT from 9.8 to 23.6 nm. The conversion efficiency of the cell made from TiO₂ NT, 12.9 nm in diameter, was enhanced by 12% compared to that of the smallest NT. These results suggested that the photovoltaic performance improved by the suppression of photogenerated charge recombination in spite of a 25.3% reduction in the specific surface area. In addition, larger TiO₂ NTs could be utilized as a scattering layer on the top of the TiO₂ nanoparticulate working electrode. It was observed that this controlled TiO₂ photoelectrode architecture exhibited enhanced conversion efficiency without TiCl₄ treatment.