Modification of Mesoporous TiO2 Films by Electrochemical Doping: Impact on Photoelectrocatalytic and Photovoltaic Performance

The effect of reductive electrochemical doping of nanocrystalline TiO2 electrodes on their photoelectrocatalytic properties and their performance in dye-sensitized solar cells is studied. It is observed that accumulation of negative charge (compensated by proton insertion from the supporting electrolyte) leads to a photocurrent increase for water oxidation. Furthermore, an enhanced photoconversion efficiency in dye-sensitized solar cells is observed for the doped electrodes with respect to the unmodified ones. The effect has been analyzed using small-perturbation electrochemical techniques (impedance spectroscopy, intensity-modulated photovoltage, and photocurrent spectroscopy). The results indicate that the better photoelectrocatalytic and photovoltaic efficiency is due to a more rapid electron transport combined with reduced recombination, contributing to improved electron collection. Furthermore, an enhancement in electron injection is also inferred from the analysis of the present results.