Pseudohalogens for dye-sensitized TiO2 photoelectrochemical cells

In this paper, we report on the preparation and characterization of two pse udohalogen redox couples for dye-sensitized TiO2 photoelectrochemical cells . The equilibrium potentials of the (SeCN)(2)/SeCN- and (SCN)(2)/SCN- coupl es are respectively 0.19 and 0.43 V more positive than for the I-3(-)/I- co uple, providing the opportunity to determine the influence of the redox pot ential on the open circuit photovoltage. With the sensitizer cis-Ru(dcb)(2) (NCS)(2) (N3), the incident photon-to-current conversion efficiency was 20% for the (SeCN)(2)/SeCN- couple and 4% for the (SCN)(2)/SCN- couple. Transi ent absorbance measurements showed that the quantum yield for electron inje ction is independent of the pseudohalogen redox couple and that the regener ation rates of the dye decrease in the order I- > SeCN- > SCN-. The effects of the redox potential on open circuit photovoltage were determined by ind ependent measurement of the dependence of the sensitized TiO2 working elect rode and the platinum counter electrode potentials on the cell voltage.