title: Atomic level resolution of dye regeneration in the dye-sensitized solar cell.
abstract: Two donor-acceptor organic dyes have been synthesized that differ only by a two-heteroatom change from oxygen to sulfur within the donor unit. The two dyes, (E)-3-(5-(4-(bis(4-(hexyloxy)phenyl)amino)phenyl)thiophen-2-yl)-2-cyanoprop-2-enoic acid (Dye-O) and (E)-3-(5-(4-(bis(4-(hexylthio)phenyl)amino)phenyl)thiophen-2-yl)-2-cyanoprop-2-enoic acid) (Dye-S), were tested in solar cell devices employing both I(3)(-)/I(-)-based and [Co(bpy)(3)](3+/2+) redox mediators. Power conversion efficiencies over 6% under simulated AM 1.5 illumination (1 Sun) were achieved in both electrolytes. Despite similar optical and redox properties for the two dyes, a consistently higher open-circuit voltage (V(oc)) was measured for Dye-S relative to Dye-O. The improved efficiency observed with Dye-S in an iodide redox mediator is against the commonly held view that sulfur atoms promote charge recombination attributed to inner-sphere interactions. Detailed mechanistic studies revealed that this is a consequence of a 25-fold enhancement of the regeneration rate constant that enhances the regeneration yield under open circuit conditions. The data show that a high short circuit photocurrent does not imply optimal regeneration efficiency as is often assumed.
authors.affiliation: Department of Chemistry and Centre for Advanced Solar Materials, University of Calgary, 2500 University Drive Northwest, Calgary T2N 1N4, Canada.
authors.forename: Kiyoshi C D
authors.initials: KC
authors.lastname: Robson
authors.forename: Ke
authors.initials: K
authors.lastname: Hu
authors.forename: Gerald J
authors.initials: GJ
authors.lastname: Meyer
authors.forename: Curtis P
authors.initials: CP
authors.lastname: Berlinguette
mesh_terms: D004396:Coloring Agents / Q000138:chemical synthesis* / Q000737:chemistry; D011211:Electric Power Supplies; D008958:Models, Molecular; D015394:Molecular Structure; D012993:Solar Energy
chemical_list: D004396:Coloring Agents