title: 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 I(3)(-)/I(-) redox shuttle used in dye-sensitized solar cells. A cobalt complex using tridendate ligands [Co(bpy-pz)(2)](3+/2+)(PF(6))(3/2) as redox mediator in combination with a cyclopentadithiophene-bridged donor-acceptor dye (Y123), adsorbed on TiO(2), 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 I(3)(-)/I(-) redox shuttle.
authors.affiliation: Laboratory for Photonics and Interfaces, Institute of Chemical Sciences and Engineering, School of Basic Sciences, Ecole Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland.
authors.forename: Jun-Ho
authors.initials: JH
authors.lastname: Yum
authors.forename: Etienne
authors.initials: E
authors.lastname: Baranoff
authors.forename: Florian
authors.initials: F
authors.lastname: Kessler
authors.forename: Thomas
authors.initials: T
authors.lastname: Moehl
authors.forename: Shahzada
authors.initials: S
authors.lastname: Ahmad
authors.forename: Takeru
authors.initials: T
authors.lastname: Bessho
authors.forename: Arianna
authors.initials: A
authors.lastname: Marchioro
authors.forename: Elham
authors.initials: E
authors.lastname: Ghadiri
authors.forename: Jacques-E
authors.initials: JE
authors.lastname: Moser
authors.forename: Chenyi
authors.initials: C
authors.lastname: Yi
authors.forename: Md K
authors.initials: MK
authors.lastname: Nazeeruddin
authors.forename: Michael
authors.initials: M
authors.lastname: Grätzel
mesh_terms: D003035:Cobalt / Q000737:chemistry*; D004396:Coloring Agents / Q000737:chemistry; D017097:Electric Impedance; D011211:Electric Power Supplies; D004563:Electrochemistry / Q000379:methods; D004566:Electrodes; D008024:Ligands; D008422:Materials Testing; D008956:Models, Chemical; D010084:Oxidation-Reduction; D012993:Solar Energy; D013472:Sunlight; D014025:Titanium / Q000737:chemistry
chemical_list: D004396:Coloring Agents; D008024:Ligands; C009495:titanium dioxide; D003035:Cobalt; D014025:Titanium