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Organic Redox Couples and Organic Counter Electrode for Efficient Organic Dye-Sensitized Solar Cells
KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
KTH, School of Chemical Science and Engineering (CHE), Chemistry, Inorganic Chemistry (closed 20110630).
KTH, School of Chemical Science and Engineering (CHE), Chemistry, Inorganic Chemistry (closed 20110630).
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2011 (English)In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 133, no 24, 9413-9422 p.Article in journal (Refereed) Published
Abstract [en]

A series of organic thiolate/disulfide redox couples have been synthesized and have been studied systematically in dye-sensitized solar cells (DSCs) on the basis of an organic dye (TH305). Photophysical, photoelectrochemical, and photovoltaic measurements were performed in order to get insights into the effects of different redox couples on the performance of DSCs. The polymeric, organic poly(3,4-ethylenedioxythiophene) (PEDOT) material has also been introduced as counter electrode in this kind of noniodine-containing DSCs showing a promising conversion efficiency of 6.0% under AM 1.5G, 100 light illumination. Detailed studies using electrochemical impedance spectroscopy and linear-sweep voltammetry reveal that the reduction of disulfide species is more efficient on the PEDOT counter electrode surface than on the commonly used platinized conducting glass electrode. Both pure and solvated ionic-liquid electrolytes based on a thiolate anion have been studied in the DSCs. The pure and solvated ionic-liquid-based electrolytes containing an organic redox couple render efficiencies of 3.4% and 1.2% under 10 light illumination, respectively.

Place, publisher, year, edition, pages
2011. Vol. 133, no 24, 9413-9422 p.
Keyword [en]
National Category
Other Basic Medicine
URN: urn:nbn:se:kth:diva-36232DOI: 10.1021/ja2030933ISI: 000291915100055ScopusID: 2-s2.0-79959233553OAI: diva2:430638

QC 20110711

Available from: 2011-07-11 Created: 2011-07-11 Last updated: 2016-04-22Bibliographically approved
In thesis
1. Liquid Redox Electrolytes for Dye-Sensitized Solar Cells
Open this publication in new window or tab >>Liquid Redox Electrolytes for Dye-Sensitized Solar Cells
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis focuses on liquid redox electrolytes in dye-sensitized solar cells (DSCs). A liquid redox electrolyte, as one of the key constituents in DSCs, typically consists of a redox mediator, additives and a solvent. This thesis work concerns all these three aspects of liquid electrolytes, aiming through fundamental insights to enhance the photovoltaic performances of liquid DSCs.

Initial attention has been paid to the iodine concentration effects in ionic liquid (IL)-based electrolytes. It has been revealed that the higher iodine concentration required in IL-based electrolytes can be attributed to both triiodide mobility associated with the high viscosity of the IL, and chemical availability of triiodide. The concept of incompletely solvated ionic liquids (ISILs) has been introduced as a new type of electrolyte solvent for DSCs. It has been found that the photovoltaic performance of ISIL-based electrolytes can even rival that of organic solvent-based electrolytes. And most strikingly, ISIL-based electrolytes provide highly stable DSC devices under light-soaking conditions, as a result of the substantially lower vapor pressure of the ISIL system. A significant synergistic effect has been observed when both guanidinium thiocyanate and N-methylbenzimidazole are employed together in an IL-based electrolyte, exhibiting an optimal overall conversion efficiency.

Tetrathiafulvalene (TTF) has been investigated as an organic iodine-free redox couple in electrolytes for DSCs. An unexpected worse performance has been observed for the TTF system, albeit it possesses a particularly attractive positive redox potential. An organic, iodine-free thiolate/disulfide system has also been adopted as a redox couple in electrolytes for organic DSCs. An impressive efficiency of 6.0% has successfully been achieved by using this thiolate/disulfide redox couple in combination with a poly (3, 4-ethylenedioxythiophene) (PEDOT) counter electrode material under full sunlight illumination (AM 1.5G, 100 mW/cm2). Such high efficiency can even rival that of its counterpart DSC using a state-of-the-art iodine-based electrolyte in the systems studied.The cation effects of lithium, sodium and guanidinium ions in liquid electrolytes for DSCs have been scrutinized. The selection of the type of cations has been found to exert quite different impacts on the conduction band edge (CB) of the TiO2 and also on the electron recombination kinetics, therefore resulting in different photovoltaic behavior.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2012. 60 p.
Trita-CHE-Report, ISSN 1654-1081 ; 2012:2
dye-sensitized solar cells, electrolytes, ionic liquids, redox couples, additives
National Category
Inorganic Chemistry
urn:nbn:se:kth:diva-64139 (URN)978-91-7501-231-5 (ISBN)
Public defence
2012-02-16, F3, Lindstedtsvägen 26, KTH, Stockholm, 10:00 (Finnish)
QC 20120124Available from: 2012-01-24 Created: 2012-01-24 Last updated: 2012-01-24Bibliographically approved

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