Nanowires could 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,” said Dr. Magnus Barnstorm, a researcher in semiconductor physics from Lund University in Sweden and the principal author of a paper on the subject.
Research on solar cell nanowires is on the rise globally. Until now the unattained dream figure was ten percent efficiency – but now Barnstorm said he and his team reached 13.8 percent efficiency.
The nanowires consist of the semiconductor material indium phosphate and work like antennae that absorb sunlight and generate power. The nanowires assemble on surfaces of one square millimeter 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 not yet made it beyond the laboratory, but the plan is the technology could work in large solar power plants in sunny regions such as the southwestern USA, southern Spain and Africa.
Lund researchers identified the ideal diameter of the nanowires and how to synthesize 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 nanometer too small their function is significantly impaired,” Barnstorm said.
The silicon solar cells 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 is that one single material can only absorb part of the spectrum of the light.
Research carried out alongside that on nanowire technology therefore 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 they become extremely expensive and can therefore only work 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 come together with much less effort, which offers higher efficiency at a low cost. The process is also less complicated. The researchers said the nanowires can generate power at the same level as a thin film of the same material, even if they only cover around 10 percent of the surface rather than 100 percent.