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International Journal of Photoenergy
Volume 2017, Article ID 7594869, 14 pages
Research Article

Organic Dyes Containing Coplanar Dihexyl-Substituted Dithienosilole Groups for Efficient Dye-Sensitised Solar Cells

1SFI Strategic Research Cluster in Solar Energy Conversion, UCD School of Chemical and Bioprocess Engineering, University College Dublin, Dublin 4, Ireland
2SFI Strategic Research Cluster in Solar Energy Conversion, Department of Chemical Sciences and Bernal Institute, University of Limerick, Limerick, Ireland
3Laboratoire de Photonique et Interfaces (LPI), Ecole Polytechnique Fédérale de Lausanne, 1015 Lausanne, Switzerland

Correspondence should be addressed to Edmond Magner;, Niall J. English; ei.dcu@hsilgne.llain, and K. Ravindranathan Thampi; ei.dcu@ipmaht.nahtanardnivar

Received 20 October 2016; Accepted 20 February 2017; Published 4 May 2017

Academic Editor: Bill Pandit

Copyright © 2017 Ciaran Lyons et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


A chromophore containing a coplanar dihexyl-substituted dithienosilole (CL1) synthesised for use in dye-sensitised solar cells displayed an energy conversion efficiency of 6.90% under AM 1.5 sunlight irradiation. The new sensitiser showed a similar fill factor and open-circuit voltage when compared with N719. Impedance measurements showed that, in the dark, the charge-transfer resistance of a cell using CL1 in the intermediate-frequency region was higher compared to N719 (69.8 versus 41.3 Ω). Under illumination at AM 1.5G-simulated conditions, the charge-transfer resistances were comparable, indicative of similar recombination rates by the oxidised form of the redox couple. The dye showed instability in ethanol solution, but excellent stability when attached to TiO2. Classical molecular dynamics indicated that interactions between ethanol and the dye are likely to reduce the stability of CL1 in solution form. Time-dependent density functional theory studies were performed to ascertain the absorption spectrum of the dye and assess the contribution of various transitions to optical excitation, which showed good agreement with experimental results.