In a recent study, researchers from Lund University in Sweden have shown
how nanowires could pave the way for more efficient and cheaper solar cells. This
finding first shows that it is possible to use nanowires to manufacture solar
cells.
Research on solar cell nanowires is on the rise globally. Until now the
unattained dream figure was ten per cent efficiency; but now scientists are
able to report an efficiency 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. The nanowires are
assembled on surfaces of one square millimetre which can hold 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 that the technology could be used in large solar power plants in sunny
regions.
The Lund researchers have now managed to identify 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 nanometre, their function is
significantly impaired. The silicon solar cells that are used to supply
electricity for domestic use are relatively cheap, but inefficient because they
are only able to utilise 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 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 therefore only be used in applications 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.
In this study, 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.
For further studies:
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