Kinetics of the Regeneration by Iodide of Dye Sensitizers Adsorbed on Mesoporous Titania

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• 作者：Jo毛l Teuscher ; Arianna Marchioro ; Julien Andr猫s ; Lo茂c M. Roch ; Mingfei Xu ; Shaik M. Zakeeruddin ; Peng Wang ; Michael Gr盲tzel ; Jacques-E. Moser
• 刊名：Journal of Physical Chemistry C
• 出版年：2014
• 出版时间：July 31, 2014
• 年：2014
• 卷：118
• 期：30
• 页码：17108-17115
• 全文大小：320K
• ISSN：1932-7455

文摘

Regeneration of dye sensitizer molecules by reducing species contained in the electrolyte is a key mechanism in liquid dye-sensitized solar cells because it competes kinetically with a detrimental charge recombination process. Kinetics of the reduction by iodide ions of the oxidized states (S<sup>+sup>) of two Ru<sup>IIsup> complex dyes and four organic 蟺-conjugated bridged donor鈥揳cceptor sensitizers were examined as a function of the electrolyte concentration. Results show that two different cases can be distinguished. A sublinear behavior of the regeneration rate and a plateau value reached at high bulk iodide concentrations were found for N820 ruthenium dye and interpreted as being due to an associative interaction involving the formation of (S<sup>+sup>, I<sup>鈥?/sup>)路路路I<sup>鈥?/sup> surface complexes prior to the reaction. On the other hand, feeble reaction rates at low electrolyte concentrations and a superlinear behavior are observed predominantly for the organic dyes, pointing to a repulsive interaction between the dyed surface and iodide anions. At higher iodide bulk concentration, a linear behavior is reached, providing an estimate of a second-order rate constant. A correlation of these two opposite behaviors with the structure of the dye is observed, emphasizing the role of sulfur atoms in the association of I<sup>鈥?/sup> anions in the dye-sensitized layer. These findings allow for a better understanding of the dye鈥揺lectrolyte interaction and of the effect of the iodide concentration on the photovoltaic performances of dye-sensitized solar cells.