Swedish engineers claim nanowire breakthrough in solar cell research

Posted by Thomas Anderson

Researchers from Lund University in Sweden have successfully demonstrated how nanowires could potentially be used to pave the way for more efficient and cheaper solar cells.

"Our findings are the first to show that it really is possible to use nanowires to manufacture solar cells," explained semiconductor physics researcher Magnus Borgström.

R&D for solar cell nanowires is on the rise globally. Until now the unattained target figure was ten per cent efficiency - but now Dr. Borgström and his colleagues have confirmed an efficiency rating of 13.8 per cent.

"The nanowires are made of the semiconductor material indium phosphide and work like antennae that absorb sunlight and generate power," said Borgström.

"The nanowires are assembled on surfaces of one square millimetre that each house four million nanowires. A nanowire solar cell can produce an effect per active surface unit several times greater than today's silicon cells."

According to Borgström, nanowire solar cells have not yet made it beyond the laboratory, but the researchers are hoping the technology could ultimately be used in large solar power plants in sunny regions such as the south-western USA, southern Spain and Africa.

Indeed, the team has managed to identify the ideal diameter of the nanowires and how to synthesize them. However, the right size is essential for the nanowires to absorb as many photons as possible. To be sure, if they are just a few tenths of a nanometre too small their function is significantly impaired.

Interestingly, the silicon solar cells that are used to supply electricity for domestic use are relatively cheap, but inefficient because they are only able to utilize a limited part of the effect of the sunlight. The reason? One single material can only absorb part of the spectrum of the light.

Therefore, research conducted alongside the above-mentioned nanowire initiative hopes to combine different types of semiconductor material to make efficient use of a broader part of the solar spectrum. Nevertheless, there is a disadvantage to this approach, namely they become extremely expensive and can therefore only be used in niche contexts, such as on satellites and military planes.

However, this is not the case with nanowires. Because of their small dimensions, the same sort of material combinations can be created with much less effort, which offers higher efficiency at a low cost. The process is also less complicated, as nanowires are capable of generating power at the same level as a thin film of the same material - even if they only cover around 10 per cent of the surface rather than 100 per cent.