Nanowires may help to boost solar cell efficiency

Washington, May 15 : Electrical engineers have created experimental solar cells spiked with nanowires that could lead to highly efficient thin-film solar cells of the future.

According to a report in ENN (Environmental News Network), the experimental solar cells have been developed by electrical engineers from the University of California, San Diego.

The research team chose nanowires because they can serve as electron superhighways that carry electrons kicked loose by photons of light directly to the device's electron-attracting electrode - a scenario that could boost thin-film solar cell efficiency.

As in more traditional organic polymer thin-film solar cells, the polymer material in the experimental system absorbs photons of light.

To convert this energy to electricity, each photon-absorbing electron must split apart from its hole companion at the interface of the polymer and the nanowire - a region known as the p-n junction.

Once the electron and hole split, the electron travels down the nanowire - the electron superhighway - and merges seamlessly with the electron-capturing electrode.

This rapid shuttling of electrons from the p-n junction to the electrode could serve to make future photovoltaic devices made with polymers more efficient.

The new design increases the number of electrons that make it from the light-absorbing polymer to an electrode.

"If you provide electrons with a defined pathway to the electrode, you can reduce some of the inefficiencies that currently plague thin-film solar cells made from polymer mixtures," said Clint Novotny, a recent electrical engineering Ph.D. from UC San Diego's Jacobs School of Engineering.

"More efficient transport of electrons and holes - collectively known as carriers - is critical for creating more efficient solar cells," he added.

The engineers devised a way to grow nanowires directly on the electrode. This advance allowed them to create the electron superhighways that deliver electrons from the polymer-nanowire interface directly to an electrode.

Having a more efficient method for getting electrons to their electrode means that researchers can make thin-film polymer solar cells that are a little bit thicker, and this could increase the amount of sunlight that the devices absorb.

Growing nanowires directly on untreated electrodes is an important step toward the goal of growing nanowires on cheap metal substrates that could serve as foundations for next-generation photovoltaics that conform to the curved surfaces like rooftops, cars or other supporting structures, according to the engineers.

"By growing nanowires directly on an untreated electrode surface, you can start thinking about incorporating millions or billions of nanowires in a single device. I think this is where the field is eventually going to end up," said Novotny.

ANI