A visualization of the broad-spectrum solar energy funnel. Image credit: Yan Liang

EARTHSKY // SCIENCE WIRE RELEASE DATE: NOV 26, 2012

Funneling the sun’s energy

MIT engineers propose a new way of harnessing photons for electricity, with the potential for capturing a wider spectrum of solar energy.

The quest to harness a broader spectrum of sunlight’s energy to produce electricity has taken a radically new turn, with the proposal of a “solar energy funnel” that takes advantage of materials under elastic strain.

“We’re trying to use elastic strains to produce unprecedented properties,” says Ju Li, an MIT professor and corresponding author of a paper describing the new solar-funnel concept that was published this week in the journal Nature Photonics.

In this case, the “funnel” is a metaphor: Electrons and their counterparts, holes — which are split off from atoms by the energy of photons — are driven to the center of the structure by electronic forces, not by gravity as in a household funnel. And yet, as it happens, the material actually does assume the shape of a funnel: It is a stretched sheet of vanishingly thin material, poked down at its center by a microscopic needle that indents the surface and produces a curved, funnel-like shape.

The pressure exerted by the needle imparts elastic strain, which increases toward the sheet’s center. The varying strain changes the atomic structure just enough to “tune” different sections to different wavelengths of light — including not just visible light, but also some of the invisible spectrum, which accounts for much of sunlight’s energy.

Read more: Funneling the sun’s energy | Science Wire | EarthSky.

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