Nanowires More Efficient Than Solar Cells
January 18, 2013

Researchers Find Nanowires Are Better At Making Electricity From Sunlight

Lee Rannals for — Your Universe Online

A team from Lund University in Sweden wrote in the journal Science about how nanowires could eventually make way for more efficient solar cells.

Scientists have been studying solar cell nanowires more and more, and until now, the dream figure was ten percent efficiency. However, the Swedish researchers were able to report an efficiency of 13.8 percent.

Nanowires are made of the semiconductor material indium phosphide and work like antennae that absorb sunlight and help to generate power. The nanowires are assembled on surfaces of one square millimeter, housing four million nanowires.

A nanowire solar cell is able to produce an effect per active surface unit several times greater than today's silicon cells.

Nanowire solar cells have not made it beyond the laboratory, but the plan is the technology could be used in larger solar power plants in sunny regions.

The researchers have managed to identify the ideal diameter of the nanowires and how to synthesize them. With this technology, solar energy will be able to reach new heights.

"The right size is essential for the nanowires to absorb as many photons as possible. If they are just a few tenths of a [nanometer] too small their function is significantly impaired," Magnus Borgström, a researcher in semiconductor physics and the principal author, said in a statement.

The silicon solar cells are used to help supply electricity for domestic use and they are relatively cheap. However, they are also inefficient because they are only able to utilize a limited part of the effect of the sunlight.

Scientists hope to combine different types of semiconductor materials to make efficient use of a broader part of the solar spectrum. The disadvantage of this is that they become extremely expensive and can only be used in niche contexts.

Because of their small dimensions, the same material combinations can be created with less effort, offering higher efficiency at a low cost. The process is also less complicated.

The researchers wrote in Science that the nanowires are able to generate power at the same level as a thin film of the same material, even if they only cover around ten percent of the surface, rather than 100 percent.

"I am very proud of such a great result — it has well exceeded our expectations. We will of course continue the research on nanowire solar cells and hope to achieve an even higher level of efficiency than the 13.8 per cent that we have now reported", Knut Deppert, coordinator of the project, said in the statement.