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Measured Binding Coefficients for Iodine and Ruthenium Dyes; Implications for Recombination in Dye Sensitised Solar Cells

Measured Binding Coefficients for Iodine and Ruthenium Dyes; Implications for Recombination in Dye Sensitised Solar Cells

Xiaoe Li, Anna Reynal, Piers Barnes, Robin Humphry-Baker, Shaik Mohammed Zakeeruddin, Filippo De Angelis, Brian C O'Regan

Phys Chem Chem Phys. 2012 Nov 28;14(44):15421-8.

PMID: 23070136

Abstract:

We have measured the binding coefficients of iodine to three dyes used in Dye Sensitised Solar Cells (DSSCs). Binding coefficients are quantified via the effect of iodine binding on the UV-vis spectrum of the dye. From iodine titration curves of dye sensitised TiO(2) films we find that the binding coefficients of iodine to the dyes C101, N719 and AR24 (vide infra) are in the range of 2000-4000 M(-1). From FTIR results and molecular modelling we show the iodine binds to the thiocyanate group in all these dyes. For the AR24 dye we present evidence that iodine also binds to the amine moiety on this dye. With these binding coefficients we show that the dye-iodine complex will be present at much higher concentrations than free iodine in the pore structure of a DSSC. As we have recently shown that iodine (rather than tri-iodide) is the dominant acceptor in electron recombination, the concentration dye-iodine complexes could influence recombination rates and thus V(oc). By comparison of recombination data on full cells, we show that AR24 accelerates recombination by a factor of 7 over N719, presumably due to the iodine binding to the amine group. We leave open the question why iodine binding to the amine group seems to have a stronger effect on the recombination than does binding to the thiocyanate.

Chemicals Related in the Paper:

Catalog Number	Product Name	Structure	CAS Number	Price
AP13311450	Tetrabutylammonium triiodide		13311-45-0	Price

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