Researchers at the California Institute of Technology (Caltech) have created a new type of flexible solar cell that enhances the absorption of sunlight while maintaining high efficiency. The solar cell uses arrays of long, thin silicon wires embedded in a polymer substrate, requiring a fiftieth of the silicon used by conventional silicon solar cells.
The silicon-wire arrays absorb up to 96 percent of incident sunlight at a single wavelength and 85 percent of total collectible sunlight, surpassing previous optical microstructures developed to trap light.
The silicon wire arrays created by the Caltech team are able to convert between 90 and 100 percent of the photons they absorb into electrons. In the solar cells, each silicon wire is independently a high-efficiency; high-quality solar cell says Harry Atwater, Howard Hughes Professor, professor of applied physics and materials science, and director of Caltech’s Resnick Institute.
Each wire measures between 30 and 100 microns in length and only 1 micron in diameter. “The entire thickness of the array is the length of the wire, but in terms of area or volume, just 2 percent of it is silicon, and 98 percent is polymer.” says Professor Atwater.
As silicon is an expensive component of a conventional solar cell, this technology using just one-fiftieth of the amount will mean solar cells would be much cheaper to produce. The flexibility of the cells will also reduce price as flexible thin films can be manufactured in a roll-to-roll process, an inherently lower-cost process than the manufacture of rigid, conventional solar cells.
The Caltech team will now focus on increasing the operating voltage and the overall size of the solar cell and Professor Atwater says the team is well on its way to demonstrating that conventional sized cells will work just as efficiently as the small versions already produced.
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