A new solar cell can produce the same amount of energy as the best conventional solar panels while using less expensive material.

The novel flexible device could help make solar cells far more practical for products ranging from sunroofs to clothing, scientists say.

"It could be extremely rugged – you could roll it up, even perforate it, shoot holes in it with a gun, and it'd still operate, whereas normal crystalline silicon would just shatter like glass," said researcher Harry Atwater, an applied physicist at the California Institute of Technology at Pasadena, Calif.

Solar cells often rely on wafers of perfect silicon crystal, but these are costly. To save on crystalline silicon, Atwater and his colleagues used only one percent of the expensive material, which they grew as rods.

Each rod is only one or two millionths of a meter across – roughly one-hundredth the width of a human hair – and they are arranged vertically in a forest-like pattern.

Incoming light bounces back and forth between the rods until it gets absorbed. Particles of alumina were added between the rods to help scatter light so the rods can absorb more of it. The entire setup was embedded in a layer of transparent silicone rubber, making it flexible.

The new solar cell absorbed up to 85 percent of the usable incoming sunlight, which is comparable to conventional solar cells.

In addition, the fraction of the solar energy converted to electricity in the new device was on the order of 95 percent, "very comparable to the highest quality solar cells and well above that of other flexible thin film solar cells," Atwater said.

When it comes to making such cells on an industrial scale, Atwater foresees these being cheaper than conventional solar cells "not only because we've reduced the amount of crystalline silicon used, but the way we make it bypasses two or three expensive and energy-consuming steps."

These devices could readily get made on a large scale using existing roll-to-roll printing methods, Atwater said.

"There's a real opportunity here to be competitive in mainstream utility-scale photovoltaics where thin-film solar cells are used right now," he noted.

"We're actively pursuing commercialization opportunities at the moment."

Atwater and his colleagues detailed their findings online February 14 in the journal Nature Materials.

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