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Issue 44, 2012
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Measured binding coefficients for iodine and ruthenium dyes; implications for recombination in dye sensitised solar cells

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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 TiO2 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 Voc. 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.

Graphical abstract: Measured binding coefficients for iodine and ruthenium dyes; implications for recombination in dye sensitised solar cells

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Publication details

The article was received on 24 Sep 2012, accepted on 24 Sep 2012 and first published on 26 Sep 2012


Article type: Paper
DOI: 10.1039/C2CP43347H
Citation: Phys. Chem. Chem. Phys., 2012,14, 15421-15428
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    Measured binding coefficients for iodine and ruthenium dyes; implications for recombination in dye sensitised solar cells

    X. Li, A. Reynal, P. Barnes, R. Humphry-Baker, S. M. Zakeeruddin, F. De Angelis and B. C. O'Regan, Phys. Chem. Chem. Phys., 2012, 14, 15421
    DOI: 10.1039/C2CP43347H

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