A cobalt complex redox shuttle for dye-sensitized solar cells with high open-circuit potentials

Abstract

Dye-sensitized solar cells are a promising alternative to traditional inorganic semiconductor-based solar cells. Here we report an open-circuit voltage of over 1,000 mV in mesoscopic dye-sensitized solar cells incorporating a molecularly engineered cobalt complex as redox mediator. Cobalt complexes have negligible absorption in the visible region of the solar spectrum, and their redox properties can be tuned in a controlled fashion by selecting suitable donor/acceptor substituents on the ligand. This approach offers an attractive alternate to the traditional I3-/I- redox shuttle used in dye-sensitized solar cells. A cobalt complex using tridendate ligands [Co(bpy-pz)2]3+/2+ (PF6)3/2 as redox mediator in combination with a cyclopentadithiophene-bridged donor-acceptor dye (Y123), adsorbed on TiO2, yielded a power conversion efficiency of over 10% at 100 mW cm-2. This result indicates that the molecularly engineered cobalt redox shuttle is a legitimate alternative to the commonly used I3-/I- redox shuttle. © 2012 Macmillan Publishers Limited. All rights reserved.