Hybrid Carbon Nanotubes−TiO2 Photoanodes for High Efficiency Dye-Sensitized Solar Cells

We describe a fast and effective procedure for
the preparation of high efficiency hybrid photoanodes for dye-
sensitized solar cells (DSCs), based on nanocrystalline TiO2
with limited addition of multiwall carbon nanotubes (CNTs).
The mixing process between CNTs and TiO2 nanoparticles is
almost instantaneous, which makes it feasible for large-scale
fabrication. Enhanced electron lifetime and reduced charge
recombination lead to highly increased short circuit current
density and overall photoconversion efficiency (from 13.6 mA
cm−2 to 16.0 mA cm−2 and from 7.0% to 9.0%, respectively, considering the bare TiO2 and the optimum CNTs concentration, which is 0.010 wt %), while the small reduction in open circuit photovoltage does not significantly affect cell performances. This result is remarkable since a standard dye molecule (N719) was used and no chemical treatments of the photoanodes prior to cell fabrication were applied (i.e., soaking in TiCl4 to boost open circuit photovoltage).