July 14, 2008

Window generates electricity

A new device based on an older solar technology produces inexpensive solar energy by capturing layers of light and concentrating them sideways.

The device is an update of a solar concentrator made from a dye-infused sheet of plastic surrounded by ordinary solar cells. In this older device light hits the plastic and is shunted sideways into the solar cells. The new solar concentrator replaces the plastic with glass that's coated with a transparent organic semiconductor material.

The transparent coating absorbs light and emits it at a different wavelength. The new wavelength is shunted sideways through the glass to the solar cells. Stack several concentrators that are tuned to absorb different wavelengths of light and you can extract more energy from the same sunlight.

The new device converts as much as 6.8 percent of the sunlight that hits it to electricity. This is well below the 20 to 30 percent conversion rate of more expensive silicon solar cells but 10 times higher than older versions of the concentrator, and it's high enough to be useful. The concentrators also doesn't need to be turned to face the sun, which means they could be used as electricity-generating windows in buildings.

Research paper:
High-Efficiency Organic Solar Concentrators for Photovoltaics
Science, July 11, 2008

Researchers' homepage:
Soft Semiconductor Group, MIT

Related stories and briefs:
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