Gallium Arsenide Nanowires Boost Solar Cell Efficiency

Anna Fontcuberta i Morral (EPFL)

University and industrial researchers in Switzerland and Denmark developed a new type of solar cell that in lab tests captures more light and generates more power than traditional silicon cells. The team from Ecole Polytechnique Fédérale de Lausanne (EPFL) in Lausanne, Switzerland, Neils Bohr Institute at University of Copenhagen, and the Danish spin-off company SunFlake A/S in Copenhagen, published its findings in a recent issue of the journal Nature Photonics; paid subscription required.

The EPFL researchers from its Laboratory of Semiconductor Materials, led by Anna Fontcuberta i Morral (pictured left), and their colleagues in Denmark, used tiny nanoscale filaments of gallium arsenide, a compound of the elements gallium and arsenic, in their solar cells. The team configured the nanowires, measuring from tens to hundreds of nanometers — 1 nanometer equals one billionth of a meter or about the size of viruses — vertically on prototype solar cells.

Gallium arsenide is a better converter of light to energy than silicon, but is much more expensive than silicon, which has limited its use in semiconductors and solar cells. The vertical configuration of the nanowires enables the filaments to act as light funnels, however, dramatically increasing the light capturing capability of the prototype cells.

The researchers found the prototype solar cells can capture 12 times more light than the typical silicon solar cell. “These nanowires capture much more light than expected,” says Fontcuberta.

When arrayed in solar panels, the gallium arsenide nanowire cells also showed to be more efficient energy producers than traditional silicon solar panels. Panels made with the prototype solar cells achieved 33 percent efficiency, turning one-third of the light captured into electric power. Today’s silicon solar cells can generate electric power with at most 20 percent efficiency.

Configuring the gallium arsenide as vertical nanowires also makes it possible to use much less of the costly material, as little as 10,000 times less, according to the researchers. The team estimates the cost of gallium arsenide in this form at $10 per square meter.

In the following video, Fontcuberta tells more about this solar technology.

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