Pseudohalogens for Dye-Sensitized TiO₂ Photoelectrochemical Cells

Abstract

In this paper, we report on the preparation and characterization of two pseudohalogen redox couples for\ndye-sensitized TiO₂ photoelectrochemical cells. The equilibrium potentials of the (SeCN)₂/SeCN^- and (SCN)₂/SCN^- couples are respectively 0.19 and 0.43 V more positive than for the I₃^-/I^- couple, providing the\nopportunity to determine the influence of the redox potential on the open circuit photovoltage. With the\nsensitizer <i>cis</i>-Ru(dcb)₂(NCS)₂ (N3), the incident photon-to-current conversion efficiency was 20% for the\n(SeCN)₂/SeCN^- couple and 4% for the (SCN)₂/SCN^- couple. Transient absorbance measurements showed\nthat the quantum yield for electron injection is independent of the pseudohalogen redox couple and that the\nregeneration rates of the dye decrease in the order I^- > SeCN^- > SCN^-. The effects of the redox potential\non open circuit photovoltage were determined by independent measurement of the dependence of the sensitized\nTiO₂ working electrode and the platinum counter electrode potentials on the cell voltage.