http://www.abc.net.au/tv/newinventors/txt/s3008638.htm



The invention involves the development of a completely printable organic solar cell based on semiconducting polymer nanoparticles dispersed in water. Essentially these tiny particles in suspension are a water-based paint, which can be printed or coated over large areas. Light shining on an organic solar cell produces positive and negative charges that can only be separated at interfaces between the polymer components in the cell. In an organic solar cell, the positive and negative charges can only travel a very short distance (around 10 nanometres or a millionth of a centimetre) before they recombine to give off light or heat, which is not very useful! So, in order obtain useful energy from an organic solar cell, these light-generated charges must be separated and collected within a few nanometres. Fortunately, this separation readily occurs at interfaces, or junctions, to produce two separated positive and negative charges, which then travel to the electrodes (or contacts) and then out of the solar cell to produce an electrical current. The most efficient devices consist of a mixture (or blend) of a p-type semi-conducting polymer, which readily accepts and transfers positive charges, and a n-type material that readily accepts and transfers negative charges. By creating tiny nanoparticles, we have both controlled the maximum distances that the charges have to travel before coming to an interface and allowed the coatings to be made out of water – a non-hazardous solvent!

The key advantage of these organic solar cells is that they can be printed at high speeds across large areas using roll-to-roll processing techniques thus creating the tantalising vision of coating every roof and other suitable building surface with photovoltaic materials at extremely low cost. In the first instance these coatings will be put onto plastic sheets that can be placed on the roof of a house. However, in the longer term, it may be possible to directly paint a roof or building surface. Organic solar cells will use the same standard inverter technology used by conventional solar cells to connect the electricty grid network. The organic solar cells are coated from water onto recyclable plastic sheets such as PET and thus are completely environmentally friendly. Ultimately, this invention will mean that every household in Australia will be able to generate its own electricity from a sustainable and renewable resource, using a paint coating on their own roof.