Lego-inspires more efficient solar cells
- Available online 8 December 2013
Solar panels with Lego-like aluminium studs produce a quarter more electrical current from sunlight than their flat counterparts, find a team of international researchers.
Most solar cells have thick layers of materials able to absorb sunlight. But these absorbing materials are expensive, making up to half the cost of a solar panel. ‘To drive down prices new technologies have focused on using thin layers of the material, but they absorb less light and are not yet efficient enough for the market,’ explains team member Nicholas Hylton from Imperial College London, UK. ‘Novel ideas are required to increase the amount of light absorbed by thin-film solar cells.’
Tiny gold or silver studs placed on the surface of solar cells have previously been shown to slightly increase efficiency. The studs bend and trap light for longer inside the absorbing material. The more time the light beams spend inside the material, the more energy is extracted. At a microscopic level these studs look like the interlocking children's building blocks called Lego.
The efficiency boost was however limited by the type of metal used for the studs. ‘The [previous] metal structures absorbed some of the light from the visible part of the solar spectrum before it was scattered into the solar cell beneath,’ Hylton told Materials Today. ‘That parasitic effect limited increases in efficiency.’
The study, published in Scientific Reports [Hylton, et al., Sci. Rep. (2013), doi:10.1038/srep02874], showed that aluminium is a better material for the studs. ‘The advantage of aluminium is that this parasitic absorption occurs in the ultraviolet part of the spectrum,’ explains Hylton. This means that the aluminium studs scatter more light in the visible region compared to silver and gold. ‘As this is where we are able to convert most energy from sunlight, we can get a boost in the electrical current produced by the device by as much as 22% compared to a device without nanostructures.’
An additional advantage of aluminium is that it is cheaper and more abundant that silver and gold.
The next step is to attempt combining the Lego-inspired material with more conventional anti-reflection coatings, says Hylton. Anti-reflection coatings stop light bouncing off solar panels before it can be absorbed. ‘If we can do this successfully then it may be possible to make thin, highly efficient solar cells at a competitive price.’
Copyright © 2013 Published by Elsevier Ltd.