title: Dye-sensitized SnO2 electrodes with iodide and pseudohalide redox mediators.
abstract: Dye-sensitized mesoporous nanocrystalline SnO2 electrodes and the pseudohalogen redox mediator (SeCN)2/SeCN- or (SCN)2/SCN- or the halogen redox mediator I3-/I- were implemented for regenerative solar cell studies. Adsorption isotherms of the sensitizers Ru(deeb)(bpy)2(PF6)2, Ru(deeb)2(dpp)(PF6)2, and Ru(deeb2(bpz)(PF6)2, where deeb is 4,4'-diethylester-2,2'-bipyridine, dpp is 2,3-dipyridyl pyrazine, and bpz is bipyrazine, binding to the SnO2 surface were well described by the Langmuir model from which the saturation coverage, Gamma0 = 1.7 x 10(-8) mol/cm2, and surface-adduct formation constant, Kad = 2 x 10(5) M(-1), were obtained. Following excited-state interfacial electron transfer, the oxidized sensitizers were reduced by donors present in the acetonitrile electrolyte as shown by transient absorption spectroscopy. With iodide as the donor, a rate constant k > 10(8) s(-1) was measured for sensitizer regeneration. In regenerative solar cells, it was found that the incident photon-to-current conversion efficiencies and open circuit voltages (Voc) were comparable for (SeCN)2/SeCN- and I3-/I- for all three sensitizers. The Voc varied linearly with the logarithm of the short circuit photocurrent densities (Jsc), with typical correlations of approximately 50-60 mV/decade. Capacitance measurements of the SnO2 electrode in the presence of I3-/I-, (SeCN)2/SeCN- or (SCN)2/SCN- are reported.
authors.affiliation: Department of Chemistry, The Johns Hopkins University, Baltimore, Maryland 21218, USA.
authors.forename: Bryan V
authors.initials: BV
authors.lastname: Bergeron
authors.forename: Andras
authors.initials: A
authors.lastname: Marton
authors.forename: Gerko
authors.initials: G
authors.lastname: Oskam
authors.forename: Gerald J
authors.initials: GJ
authors.lastname: Meyer
mesh_terms: D000327:Adsorption; D004396:Coloring Agents / Q000737:chemistry*; D004566:Electrodes; D007454:Iodides / Q000737:chemistry*; D009942:Organometallic Compounds / Q000737:chemistry; D010084:Oxidation-Reduction; D016062:Porosity; D012428:Ruthenium / Q000737:chemistry; D018036:Selenium Compounds / Q000737:chemistry*; D012680:Sensitivity and Specificity; D013861:Thiocyanates / Q000737:chemistry*; D013997:Time Factors; D017971:Tin Compounds / Q000737:chemistry*
chemical_list: D004396:Coloring Agents; D007454:Iodides; D009942:Organometallic Compounds; D018036:Selenium Compounds; D013861:Thiocyanates; D017971:Tin Compounds; D012428:Ruthenium; C045358:stannic oxide; C031760:thiocyanate