The doctoral dissertations of the former Helsinki University of Technology (TKK) and Aalto University Schools of Technology (CHEM, ELEC, ENG, SCI) published in electronic format are available in the electronic publications archive of Aalto University - Aaltodoc.
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Performance and Stability of Dye Solar Cells on Stainless Steel

Kati Miettunen

Dissertation for the degree of Doctor of Science in Technology to be presented with due permission of the Faculty of Information and Natural Sciences for public examination and debate in Auditorium K216 at Helsinki University of Technology (Espoo, Finland) on the 23rd of October, 2009, at 12 noon.

Overview in PDF format (ISBN 978-952-248-105-4)   [1897 KB]
Dissertation is also available in print (ISBN 978-952-248-104-7)

Abstract

This study is on nanostructured dye solar cells which are easy to manufacture and use low cost materials. Dye solar cells have conventionally been deposited on conductive glass sheets. To reduce the costs and enable roll-to-roll mass production, the glass substrates should be replaced with flexible metal and plastic substrates. The change of the substrates has a profound effect on the cell, e.g. on electrochemical properties, optics, temperature treatments, and lifetime which all change when using alternative substrates.

In this work, the focus is on using stainless steel and ITO-PET substrates in dye solar cells. The electrochemical characteristics of the substrates were analyzed and the need for additional coatings to improve the performance or the stability was evaluated. The optimization of the other cell components in different metal-plastic cell configurations was also examined. An important part of the work was to decouple the effects of the different cell components on the cell performance. For this purpose, a method to study individual electrode performance based on electrochemical impedance measurements of a complete cell is presented.

Issues related to the up-scaling of the cell, namely current collection and spatial performance distribution, are also covered in this work. A novel, segmented cells configuration is presented to study the spatial performance distribution. It was discovered that there are large variations in the cell performance leading to significant efficiency losses. The spatial distribution was linked with the usual electrolyte filling technique which resulted in an uneven distribution of a common electrolyte component, 4-tert-butylpyridine.

Finally, the lifetime of the stainless steel based cells was examined. Interestingly, the cells with stainless steel photoelectrode substrates aged much faster than those with stainless steel counter electrode substrates. To examine the aging mechanisms, a segmented cell design was also developed specially for the degradation studies. With the segmented cells, it could be confirmed that the degradation of the stainless steel photoelectrode cells was not due to changes in the electrolyte. The aging of the stainless steel counter electrode cells was, on the contrary, linked with the corrosion of the stainless steel substrate by the electrolyte.

This thesis consists of an overview and of the following 6 publications:

  1. Kati Miettunen, Janne Halme, Minna Toivola, and Peter Lund. 2008. Initial performance of dye solar cells on stainless steel substrates. Journal of Physical Chemistry C, volume 112, number 10, pages 4011-4017.
  2. Kati Miettunen, Janne Halme, Paula Vahermaa, Tapio Saukkonen, Minna Toivola, and Peter Lund. 2009. Dye solar cells on ITO-PET substrate with TiO2 recombination blocking layers. Journal of The Electrochemical Society, volume 156, number 8, pages B876-B883.
  3. Kati Miettunen, Janne Halme, and Peter Lund. 2009. Spatial distribution and decrease of dye solar cell performance induced by electrolyte filling. Electrochemistry Communications, volume 11, number 1, pages 25-27.
  4. Kati Miettunen, Janne Halme, and Peter Lund. 2009. Segmented cell design for improved factoring of aging effects in dye solar cells. Journal of Physical Chemistry C, volume 113, number 23, pages 10297-10302.
  5. K. Miettunen, J. Halme, T. Saukkonen, T. Peltola, M. Toivola, and P. Lund. 2009. Performance degradation of dye solar cells on flexible stainless steel substrates. In: Proceedings of the 24th European Photovoltaic Solar Energy Conference. Hamburg, Germany. 21-25 September 2009, accepted for publication.
  6. K. Miettunen, M. Toivola, J. Halme, J. Armentia, P. Vahermaa, and P. Lund. 2007. Optimization of dye-sensitized solar cells on stainless steel. In: Proceedings of the 22nd European Photovoltaic Solar Energy Conference. Milan, Italy. 3-7 September 2007, pages 512-515.

Keywords: dye solar cell, stainless steel, nanostructures, impedance spectroscopy

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© 2009 Helsinki University of Technology

Last update 2011-05-26