Eindhoven, The Netherlands--Researchers at the Technische Universiteit Eindhoven (TU/e) are aiming to develop solar cells with an efficiency of greater than 65% using nanowires. The Dutch government has reserved EUR 1.2 million for the research.
An agency of the Ministry of Economic Affairs will grant the EUR 1.2 million to researchers Jos Haverkort, Erik Bakkers, and Geert Verbong for their research into nanowire solar cells. It is their expectation that, when combined with mirror systems, these solar cells can generate a sizeable portion of the European electricity demand if installed in Southern Europe and North Africa. The research is being conducted along with MiPlaza (part of Philips Research), which is also in Eindhoven.
Existing leading-edge thin-film solar cells made of III-V semiconductors have an efficiency that lies around 40%, but they are very expensive and are thus used only as solar panels on satellites. However, using 1000X concentrating optics, such cells can now be used cost-effectively for terrestrial applications.
The TU/e researchers expect that in ten years their nanostructured solar cells can attain an efficiency of more than 65%. They believe that nanotechnology, in combination with the use of mirror concentrators can lead to the world's most efficient solar-cell systems, costing less than 50 cents per watt peak (the present generation of solar cells costs at least three times as much).
Stacking
Nanowires make it possible to stack a number of subcells (junctions). In the setup, each subcell optimally converts a certain wavelength range to electricity. The highest yield reported until now in a nanowire solar cell is 8.4%. "We expect that a protective shell around the nanowires is the critical step towards attaining the same efficiency with nanowire solar cells as with thin-film cells," says Haverkort. He thinks that with 5 to 10 junctions he will arrive at an efficiency of 65%.
Scarcity of raw materials
In addition, the researchers expect considerable savings can be made on production costs, because nanowires grow on a cheap silicon substrate and also grow faster, which results in a lower cost of ownership of the growth equipment. In addition, using mirror concentrators will result in a sparing consumption of the scarce and thus expensive metals gallium and indium.
