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Solar energy and dye solar cells

19.11.2010

A cost-efficient way to utilize solar energy under investigation at Aalto University.

Approximately one-quarter of the world's population have no electricity supply. Solar energy, an ideal carbon-free renewable energy form is available for use in every corner of the world. The largest potential areas for solar energy use are those where consumption of energy is increasing at the fastest rate. Widespread use of solar panels is impeded by the expensive production methods of those panels. The glass base currently used in solar cells is not the easiest to handle.

Since 2002, energy-producing dye solar cells have been under development at the Aalto University School of Science and Technology. The development work aims at producing cells from cheap materials and, moreover, manufacturing them using simple methods. In addition, the cells can be built on flexible bases. The operation of the cells is based on controllable nanomaterials.

The New Energy Technologies Group led by Professor Peter Lund has investigated, among other things, optimal composition of the titanium dioxide layer that influences the efficiency of energy storage. Additionally, the research unit has examined the factors that influence the durability of these cells.

Electricity in these dye solar cells, the structure of which resemble a sandwich, is generated when the dye molecules that adhere to the surface of nanosized titanium dioxide particles get excited as the photons from solar radiation hit them. Electrons move to the titanium dioxide layer from where the current flows via a metal, plastic or glass base to an external circuit where it can be utilized as electricity.

Solar cell research by Dr. Kati Miettunen, PhD (Science), has quickly taken her to the top of the field.

In her doctoral thesis in 2009, Miettunen investigated dye solar cell substrates focusing on stainless steel. His research group includes four graduate students and some diploma students.

- Currently, we study cell-base materials that would be lighter and more flexible than steel. In addition, we are testing the suitability of plastics to create a counter pair for the metal electrode. We study plastics because the substance that reacts to light is between the electrodes. The other one of the cell walls must be transparent as the light must be able to get inside the cell, Miettunen explains.

- We also investigate which kind of metal would be the most long-lasting in the cell. We have tried different metals both as a photo electrode and as a counter electrode. Already we have found a couple of good and well-functioning metals.

- An essential part of the success in our work has been the development of new and economic research methods. We have received excellent feedback about them from our colleagues around the world.

Janne Halme and Minna Toivola are Miettunen's research colleagues, who in their own doctoral dissertation research have improved cell production technologies and studied what are the things that limit the efficiency of flexible dye solar cells.

- Aalto University's Tenure Track was a lucky break for me, Miettunen tells about her career plans. But first she is going to London for a year to work with the top experts in the field at Imperial College. One of her future colleagues in London will be Dr. Brian O'Regan who with Professor Michael Grätzel are the two original developers of the dye solar cell. The 2010 Millenium Technology Prize was awarded to Professor Michael Grätzel for his study of dye-sensitized solar cells.

Further information: http://tfy.tkk.fi/renewable/

Text: Eeva Pitkälä