Scientists say that using an elasticated thin film will mean more of the sun’s light wavelengths can be used to create power
A visualization of the broad-spectrum solar energy funnel. (Source: MIT/Yan Liang)
By Sophie Yeo
It’s time to rethink your preconceptions of what a solar panel looks like: scientists at the Massachusetts Institute of Technology have designed a “solar funnel”.
As part of a quest to harness a broader spectrum of the energy produced by the sun, the new design takes advantage of how materials when they are pulled into different shapes, capturing wavelengths of light that would slip past a standard solar panel.
“We’re trying to use elastic strains to produce unprecedented properties,” says Ju Li, an MIT professor and co-author of the paper, that was published this week in the journal Nature Photonics.
The funnel starts as a metaphor, as electrons are driven to the centre of the structure by electronic forces, instead of gravity that would push a substance through an ordinary funnel.
But, as this happens, the material actually assumes the shape of a funnel, as the stretched material sinks down towards an indent at the centre, pricked with a microscopic needle.
The pressure exerted by the needle imparts elastic strain, which increases towards the sheet’s centre. The various strains across the sheet changes the atomic structure just enough to “tune” different sections to different wavelengths of light.
This allows the funnel to register not only visible light, but also the invisible parts of the spectrum, which accounts for much of the energy contained in sunlight.
The film, MoS2, that catches the light is very thin – just a single molecule thick – but unlike its better known thin-material cousin graphene, it is a natural semiconductor and it has one crucial characteristic: bandgap. This particular property allows it to be made into solar cells.
For the moment, the solar funnel remains a theory. But it could be important in directing future research into solar technology.
“This theoretical and computational demonstration, illustrated using graphs from computational modeling, may guide future design and engineering of devices in the lab,” says En Ma, a professor of materials science and engineering at Johns Hopkins University, who was not involved in the research.