title: An alternative efficient redox couple for the dye-sensitized solar cell system.
abstract: A series of new cobalt complexes [Co(LLL)(2)X(2)] were synthesized and evaluated as redox mediators for dye-sensitized nanocrystalline TiO(2) solar cells. The structure of the ligand and the nature of the counterions were found to influence the photovoltaic performance. The one-electron-transfer redox mediator [Co(dbbip)(2)](ClO(4))(2) (dbbip = 2,6-bis(1'-butylbenzimidazol-2'-yl)pyridine) performed best among the compounds investigated. Photovoltaic cells incorporating this redox mediator yielded incident photon-to-current conversion efficiencies (IPCE) of up to 80%. The overall yield of light-to-electric power conversion reached 8 % under simulated AM1.5 sunlight at 100 W m(-2) intensity and more than 4% at 1000 W m(-2). Photoelectrodes coated with a 2 microm thick nanoporous layer and a 4 microm thick light-scattering layer, sensitized with a hydrophobic ruthenium dye, gave the best results.
authors.affiliation: Laboratory for Photonics and Interfaces Institute of Molecular and Biological Chemistry Swiss Federal Institute of Technology, 1015 Lausanne, Switzerland. herve.nusbaumer@epfl.ch
authors.forename: Hervé
authors.initials: H
authors.lastname: Nusbaumer
authors.forename: Shaik M
authors.initials: SM
authors.lastname: Zakeeruddin
authors.forename: Jacques-E
authors.initials: JE
authors.lastname: Moser
authors.forename: Michael
authors.initials: M
authors.lastname: Grätzel