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GaAs nanowire solar cells have massive potential

Mar 26, 2013
Cylindrical III-V nanowire structures are predicted to have great potential in the development of solar cells, quantum computers and other electronic products
Scientists have shown that a single nanowire can concentrate the sunlight by up to 15 times of normal sunlight intensity.

The researchers who made the discovery come from the Nano-Science Centre at the Niels Bohr Institut, Denmark and the Ecole Polytechnique Fédérale de Lausanne, Switzerland.

Surprised with the results, the team believe their latest data shows the potential for developing a new type of highly efficient solar cell.

Above, the sun's rays are drawn into a nanowire, which stands on a silicon substrate. At a given wavelength the sunlight is concentrated by up to 15 times (Credit: Niels Bohr Institute)

Due to some unique physical light absorption properties of nanowires, the limit of how much energy can be utilised from the sun's rays is higher than previously believed, say the researchers.

These results demonstrate the great potential of development of nanowire-based solar cells says Peter Krogstrup, a Ph.D. scientist who worked on the project and is one of the authors of a recent paper published in Nature Photonics.

In the past few years, the project researchers have developed and improved the quality of the nanowire crystals. These crystals have a cylindrical structure with a diameter of about 10,000 part of a human hair.

The team members believe their nanowire technology could have great potential in the development of not only solar cells, but also next generation quantum computers and other electronic products.

It turns out that the nanowires naturally concentrate the sun's rays into a very small area in the crystal by up to a factor 15.

And because the diameter of a nanowire crystal is smaller than the wavelength of the light coming from the sun, it can cause resonances in the intensity of light in and around nanowires.

Peter Krogstrup points out the resonances concentrate the sunlight, leading to a higher conversion efficiency of the sun's energy.

Various microscope images of the GaAs nanowire structure

New efficiency limit

The typical efficiency limit - the so-called "Shockley-Queisser Limit," has for many years been a landmark for solar cell efficiency among researchers, but now it seems that it may be increased.

The scientists point out that their exciting discovery could move the theoretical limits. And moving the limit by only a few percent should have a major impact on the development of solar cells, exploitation of nanowire solar rays and perhaps the extraction of energy at international level.

However, it will take some years before production of solar cells consisting of nanowires becomes a reality, acknowledges Krogstrup.

This research was conducted in collaboration with the Laboratory des Matériaux Semiconducteurs, Ecole Polytechnique Fédérale de Lausanne, the Foundation and the company SunFlake A / S.

The scientific findings reported here support results published in the journal Science in January. Here, a group of researchers from Lund, showed that the sun’s rays was sucked into the nanowires due to the high amount of power that their solar cell produced.

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