I'm going to soak up the sun.
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Posted 04.09.2014 at 10:00 am
Solar cells typically convert no more than 20 percent of incoming
energy into electricity, in part because they capture only certain
wavelengths of light. Researchers at Germany’s Fraunhofer Institute for
Solar Energy Systems have developed a solar cell that converts
44.7 percent—a new record. It consists of a lens that concentrates
sunlight onto four stacked subcells, each designed to absorb a distinct
portion of the spectrum. The team estimates it will take them another
two to three years to scale up the 5.2-millimeter prototype for use in
solar-power plants.
1.
Sunlight passes through a multifaceted lens known as a Fresnel. The
lens focuses direct sunlight, delivering the power equivalent of 297
suns to the solar cell below.
2. The first subcell, made from
gallium indium phosphide, captures photons from the shortest wavelengths
of light. The subcells beneath it contain elements capable of capturing
progressively longer wavelengths.
3. Each subcell consists of
several semiconductor layers, which create an electric field. As photons
enter, they excite electrons, freeing them from the subcell.
4.
Once the freed electrons reach the top of the stack, a metal contact
funnels them toward an output terminal as a direct current.
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