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Documents jugés intéressants
2009
Next-generation (PV) solar cells
ADIT, http://www.abc.net.au/
     Scientists have worked out how to make printable solar cells more efficient by stacking them on top of each other.
By creating a new type of dye, the researchers, led by Dr Udo Bach of Monash University in Melbourne, have produced a solar cell device that could one day provide a more affordable alternative to non-renewable energy sources.
     The findings are reported online in the journal Nature Materials.
     The team, involving scientists from Monash University, the University of Wollongong and Germany's University of Ulm, are the first to succeed in making 'stacked printable' solar cells work together to generate more power.
     Currently, printable solar cells can't capture as much of the sun's energy as traditional solar cells on the market.
     But the fact that they can be printed onto thin polymer means they're extremely cheap to make, and with further development could be used on a variety of surfaces, including water, says Bach.
     "Increasing the efficiency of these cells even slightly will make them a competitive alternative to heavy, expensive solar panels."

Working together
     "Generally you can increase the efficiency of any solar device by creating stacks of cells and putting them on top of each other, like a sandwich," says Bach.
But putting two printable solar cells together results in them cancelling each other out, unless one of the cells is inverted, he adds.
     Until now, the problem was that the inverted printable solar cells hadn't been efficient enough to create a high power device.

      By developing a new type of dye for these inverted cells, Bach and his team have shown for the first time that the efficiency of the stacked cells can exceed that of the cells on their own.
     "We've managed to show that tandem structures can occur with high efficiency, previously people had only shown that they worked," says Andrew Nattestad of Monash University, who also worked on the project.
     "Although they're still a lot less efficient than silicon solar cells, it's estimated they could be around a quarter of the cost," he adds.
First step
     According to Bach, the dye will need to be tweaked further to make the tandem devices even more efficient. Currently they can harness 2.4% of the sun's energy, whereas the more expensive silicon-based cells capture around 20%.
     "This is just the first step, but we've shown that with more work, we can create very cheap and efficient solar cells by stacking two electrodes."
     Despite having the potential to be more efficient, Bach says that the stacked printable solar cells will be only slightly more expensive than the individual ones, as they don't require additional plastic to make.
     "Printable solar cells already contain two layers of electrodes - but one of them is inactive," says Bach. "We're simply replacing the inactive one with inverted solar cells."
     "The tandem devices will still be able to be printed out cheaply by the metre and have the commercial edge of being flexible and light; they just have the potential to capture a lot more energy."