Fig. 7 shows the conversion efficiencies of both the
conventional DSSC with a single-layered nanoparticle TiO2
electrode and with the novel complex nanostructured TiO2
electrode by using different anodization time. The highest
conversion efficiency is measured in the sample with the
novel complex nanostructured TiO2 electrode by using 5
minutes of anodization time. We demonstrated that the
different photovoltaic properties observed in the DSSCs with
the novel complex nanostructured TiO2 electrodes at different
anodization time are due to the different topography of the
nanoporous TiO2 layer. The enhanced photovoltaic
performance observed in the DSSCs with novel complex
nanostructured TiO2 electrodes could be correlated with the
enlarged light scattering path, the suppressed recombination
rate between I3
- ion in electrolyte and the injected
photo-electrons in FTO, and the reduced contact resistance of
the nanostructured TiO2 electrode with FTO but the
additional series resistance of the inserted nanoporous TiO2
layer may reduce the short circuit current.