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An organic redox electrolyte to rival triiodide/iodide in dye-sensitized solar cells

Abstract

Dye-sensitized solar cells (DSCs) have achieved impressive conversion efficiencies for solar energy of over 11% with an electrolyte that contains triiodide/iodide as a redox couple. Although triiodide/iodide redox couples work efficiently in DSCs, they suffer from two major disadvantages: electrolytes that contain triiodide/iodide corrode electrical contacts made of silver (which reduces the options for the scale up of DSCs to module size) and triiodide partially absorbs visible light. Here, we present a new disulfide/thiolate redox couple that has negligible absorption in the visible spectral range, a very attractive feature for flexible DSCs that use transparent conductors as current collectors. Using this novel, iodide-free redox electrolyte in conjunction with a sensitized heterojunction, we achieved an unprecedented efficiency of 6.4% under standard illumination test conditions. This novel redox couple offers a viable pathway to develop efficient DSCs with attractive properties for scale up and practical applications.

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Figure 1: Light-induced electron transfer reactions in DSCs.
Figure 2: Photocurrent density–voltage (JV) and dark current characteristics of DSCs using T2/T or I3/I as the redox couple.
Figure 3: Spectral response of the photocurrent of DSCs using T2/T or I3/I as the redox mediator.
Figure 4: Charge-transfer dynamics at the dye-sensitized heterojunction measured by nanosecond laser flash photolysis.
Figure 5: Dynamics of charge transport and recombination derived from photovoltage and photocurrent transient decay and charge-extraction measurements.

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Acknowledgements

The authors thank P. Comte for the TiO2 film fabrication, and C. Graetzel and K. Sivula for discussions. M.W., J.-E.M., R.H.-B., S.M.Z. and M.G. thank the Swiss National Science Foundation, and N.C., L.B. and B.M. thank the Natural Sciences and Engineering Research Council of Canada for financial support.

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M.G., B.M. and S.M.Z. contributed to the conception and design of the experiments, analysis of the data and writing of the paper. N.C. and L.B. carried out the experiments and contributed to the materials. J.-E.M. and R.H.-B. analysed the data and contributed to the analysis tools. M.W. carried out the experiments, analysed the data and wrote the paper.

Corresponding authors

Correspondence to Benoît Marsan, Shaik M. Zakeeruddin or Michael Grätzel.

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The authors declare no competing financial interests.

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Wang, M., Chamberland, N., Breau, L. et al. An organic redox electrolyte to rival triiodide/iodide in dye-sensitized solar cells. Nature Chem 2, 385–389 (2010). https://doi.org/10.1038/nchem.610

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