Towards metal free counter electrodes for dye-sensitized solar cells

Thumbnail Image
Journal Title
Journal ISSN
Volume Title
School of Science | Doctoral thesis (article-based) | Defence date: 2014-05-16
Checking the digitized thesis and permission for publishing
Instructions for the author
Degree programme
54 + app. 66
Aalto University publication series DOCTORAL DISSERTATIONS, 41/2014
This thesis provides a technical overview of results from addressing the critical steps in preparing counter electrodes for dye-sensitized solar cells (DSC) on flexible substrates (mainly plastics) to pave the way towards low-cost DSCs. The aim was to develop low-temperature counter electrode inks and pastes that could be suitable for high volume manufacturing processes. A special focus was given on the mechanical stability (flexibility and adhesion) of the materials that were deposited through a low-temperature route. Different low temperature inks and pastes based on carbon composites were tested as a replacement to expensive platinum nanoparticles based catalyst layer and showed good mechanical stability, comparable photovoltaic performance and low charge transfer resistance in complete dye-sensitized solar cells. Indium doped tin oxide (ITO) layer that is normally used as a conductor on plastic substrates was successfully replaced with a single walled carbon nanotube (SWCNT) film deposited as a low-temperature curable ink on polyvinyl chloride (PVC) substrate. The SWCNT films exhibited remarkably good mechanical stability when subjected to bending and tape adhesion tests. Coating the film with a thin layer of conducting polymer poly (3, 4-ethylenedioxythiophene (PEDOT) increased its catalytic performance comparable to a reference platinum counter electrode. Relevant to scaling up DSC preparation, a two way electrolyte filling method was studied as a means to suppress performance losses that occur due to non-homogenous distribution of electrolyte components. The method enhanced the photovoltaic performance of a segmented measurement cell by up to 42% compared to traditional one way filling of the electrolyte. The aforementioned results provide pathways for the future development of robust flexible counter electrodes that can be beneficial especially from the perspective of high throughput roll-to-roll processing of flexible DSCs on polymer substrates.
Supervising professor
Lund, Peter, Prof. Aalto University, Department of Applied Physics, Finland
Thesis advisor
Halme, Janne, Dr., Aalto University, Department of Applied Physics, Finland
Miettunen, Kati, Dr., Aalto University, Department of Applied Physics, Finland
dye-sensitized solar cell, flexible substrate, ITO-PET, ITO-PEN, counter electrode, carbon composite, carbon nanotubes
Other note
  • [Publication 1]: Ghufran Hashmi, Kati Miettunen, Timo Peltola, Janne Halme, Imran Asghar, Kerttu Aitola, Minna Toivola, Peter Lund, Review of materials and manufacturing options for large area flexible dye solar cells, Renewable and Sustainable Energy Reviews 15 (2011) 3717– 3732.
  • [Publication 2]: Ghufran Hashmi, Kati Miettunen, Janne Halme, Imran Asghar, Henri Vahlman, Tapio Saukkonen, Zhu Huaijin, Peter Lund, Comparison of plastic based counter electrodes for dye sensitized solar cells, Journal of the Electrochemical Society, 159 (7) H656-H661 (2012).
  • [Publication 3]: Kati Miettunen, Minna Toivola, Ghufran Hashmi, Jyri Salpakari, Imran Asghar, Peter Lund, A carbon gel catalysts layer for the roll to roll production of dye solar cells, Carbon, 49, 528-532, (2011).
  • [Publication 4]: Syed Ghufran Hashmi, Janne Halme, Tapio Saukkonen, Eeva-Leena Rautama, Peter Lund, High performance low temperature carbon composite catalysts for flexible dye sensitized solar cells, Physical Chemistry Chemical Physics, 15, (2013) 17689-17695,
  • [Publication 5]: Syed Ghufran Hashmi, Janne Halme, Tapio Saukkanen, Peter Lund, A Single-Walled Carbon Nanotube Coated Flexible PVC Counter Electrode for Dye-Sensitized Solar Cells (Accepted for publication in Advanced Materials Interfaces).
    DOI: 10.1002/admi.201300055 View at publisher
  • [Publication 6]: Syed Ghufran Hashmi, Kati Miettunen, Antti Ruuskanen, Imran Asghar, Janne Halme and Peter Lund, Process steps towards a flexible dye solar cell module, Proceedings of the 27th European Photovoltaic Solar Energy Conference 27, pp. 2922-2924 (2012).