Programm Photovoltaik Ausgabe 2008 ... - Bundesamt für Energie BFE

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The high efficiency of the squaraine sensitizer is attributed to the particular molecular design. First, the
carboxylic acid group is part of the conjugated �-system of the dye and provides strong electronic
coupling to the conduction band of TiO2. Second, the asymmetry created by the octyl chain prevents
surface aggregation and limits self-quenching of the excited state. To the best of our knowledge, these
results represent a major breakthrough in the design and development of squaraine-based sensitizers.
National / International collaborations
Instituto CNR die Scienze e Tecnologie Molecolari (ISTM), c/o Dipartimento die Chimica, Universita di
Perugia, I-06123 Perugia, Italy.
Centre of Competence in Energy and Mobility (CCEM) of the ETH domain. Project: ThinPV. This
project is coordinated by Dr. F. Nüesch and includes 9 partners in Switzerland (see
http://ccem-ch.web.psi.ch/documents/projektbeschriebe/Beschrieb_ThinPV.pdf)
Department of Chemistry, Korea University, Jochiwon, Chungnam, 339-700, Korea.
Evaluation of 2007 and perspectives for 2008
Further to providing good absorption in the red/near IR region of the solar spectrum, squaraine dyes
may be transparent over a large region of the visible spectrum, enabling the possibility of fabricating
“photovoltaic windows”: A red/near IR absorbing photovoltaic cell used as a window, will allow visible
light to enter a building, harvesting the solar power from the red/near IR part of the spectrum. Due to
their high extinction coefficients, squaraine dyes are excellent candidates to be used as co-sensitizers
in DSCs. In our first experiments we collaborated with a Korean laboratory that provided an organic
dye absorbing in the visible domain. Power conversion efficiencies of 7.4% and 6.4% were obtained
for the co-sensitized DSCs using standard and ionic liquid electrolytes, respectively [2, 3].
In 2008 we intend to push the absorption of squaraine dyes even further to the red to up to 800 nm.
Tandem cells devices shall be constructed to further increase DSC efficiency.
Publications
[1] J. H. Yum, P. Walter, S. Huber, D. Rentsch, T. Geiger, F. Nüesch, F. De Angelis, M. Gratzel, and M. K. Nazeeruddin,
"Efficient far red sensitization of nanocrystalline TiO2 films by an unsymmetrical squaraine dye", J. Am. Chem.
Soc. 129 (34), 10320 (2007).
[2] J.-H. Yum, S.-R. Jang, P. Walter, T. Geiger, F. Nüesch, S. Kim, J. Ko, M. Grätzel, M. K. Nazeeruddin, Chem. Comm,
4680-4682 (2007).
[3] D. Kuang, P. Walter, F. Nüesch, S. Kim, J. Ko, P. Comte, S. M. Zakeeruddin, M. K. Nazeeruddin, M. Grätzel, „Cosensitization
of Orgnaic Dyes for Efficient Ionic Liquid Electrolyte-Based Dye-Sensitized Solar Cells“, Langmuir 23
(22): 10906-10909 (2007).
Efficient Far Red sensitization of Nanocrystalline TiO 2 films by an Unsymmetrical Squaraine Dye, F. Nüesch, Empa Seite 117 von 288