Titanium Carbide and Titanium Nitride-Based Nanocomposites as Efficient Catalysts for the Co2+/Co3+ Redox Couple in Dye-Sensitized Solar Cells

Two different kinds of nanocomposites were developed by electrochemical deposition of poly(3,4-ethylenedioxythiophene) (PEDOT) into porous hard template films of TiC or TiN nanoparticles, in order to evaluate their use as alternative catalysts in dye-sensitized solar cells (DSSC) utilizing a Co2+/Co3+ polypyridyl redox mediator. Cyclic voltammograms indicate that both types of nanocomposite show comparable catalytic activity to platinum-coated electrodes. However, electrochemical impedance spectroscopy (EIS) reveals that electron transfer resistances are significantly reduced with the porous nanocomposite electrodes (<1 Omega), to about an order of magnitude lower than those observed for the Pt coated electrode. As a result, DSSCs with the composite counter electrodes achieved equivalent or higher photovoltaic conversion efficiencies compared to cells with pristine PEDOT or Pt coated electrodes. In particular, the highest efficiency (8.26%) was achieved with a DSSC using a TiN-PEDOT counter electrode.