Nanowires enable production of more efficient solar cells

Researchers from Lund University in Sweden have shown how nanowires can be utilised to make cheaper and more efficient solar cells.

‘Our findings are the first to show that it really is possible to use nanowires to manufacture solar cells’, said Magnus Borgström, a researcher in semiconductor physics.

Until now, the efficiency goal for solar cell nanowires was 10 per cent, but Dr Borgström and his colleagues report an efficiency of 13.8 per cent in the journal Science.

The nanowires are made of the semiconductor material indium phosphide that absorbs sunlight and generates power. The nanowires are assembled on surfaces of 1mm² 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.

Nanowire solar cells have yet to leave a laboratory setting, but the aim is for the technology to be used in large solar power plants in regions such as the south-western US, southern Spain and Africa.

Ideal size

The Lund researchers have now managed to identify the ideal diameter of the nanowires and how to synthesise them.

‘The right size is essential for the nanowires to absorb as many photons as possible. If they are just a few tenths of a nanometre too small, their function is significantly impaired,’ said Borgström in a statement.

The silicon solar cells that are used to supply electricity for domestic use are relatively cheap but inefficient because one single material can only absorb part of the spectrum of the light.

Research carried out alongside that on nanowire technology aims to combine different types of semiconductor material to make efficient use of a broader part of the solar spectrum. The disadvantage of this is that they become expensive and can only be used in niche contexts, such as on satellites and military aircraft.

Nanowires, however, present a different scenario. Thanks to 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 said to be less complicated and the researchers have shown that the nanowires can generate 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.

The research has been carried out as part of an EU-funded project, AMON-RA, co-ordinated by Knut Deppert, professor of physics at Lund University.

Further details can be found here.