Effect of seed layer on the growth of rutile TiO2 nanorod arrays and their performance in dye-sensitized solar cells

In order to improve the performance of TiO2 photoanode-based dye sensitized solar cells (DSSCs), rutile TiO2 nanorod arrays (NRAs) were grown on SnO2:F (FTO) conductive glass coated with TiO2 seed layer by a hydrothermal method. The TiO2 seed layer was obtained by spin-coating titanium tetraisopropoxide (TTIP) isopropanol solution with concentration in the range of 0~0.075 M. Then the effect of the thin TiO2 seed layer on the crystal structure and surface morphology of TiO2 NRAs and the photoelectric conversion properties of the corresponding DSSCs were investigated. It is found that TiO2 NRAs are vertically oriented, about 1.7 μm long and the average diameter is about 35 nm for the samples derived from TTIP in the range of 0.005~0.05 M, which are more uniform and better separated from each other than those without TiO2 seed layer (average diameter 35~85 nm). The photoelectric conversion efficiency of DSSCs based on TiO2 NRAs with TiO2 seed layer is larger than that without TiO2 seed layer. Typically, the energy efficiency of DSSCs obtained from the seed solution of 0.025 M TTIP is 1.47%, about 1.8 times greater than that without TiO2 seed layer. The performance improvement is attributed to the thinner, denser and better oriented NRAs grown on seeded-FTO substrate absorbing more dye and suppressing charge recombination at the FTO substrate/electrolyte interface.