Significantly More Efficient Solar Cells Thanks To New Technique

Significant improvements to solar cell efficiency are now possible because of a new technique created by researchers at the University of Toronto.

The new technique greatly improves the efficiency of colloidal quantum dot photovoltaics, which is a design that was already looking attractive as a path to cheap, very efficient solar cells. Previously, though, these quantum dot photovoltaics were not very efficient in the infrared portion of the solar spectrum. Infrared makes up about half of the Sun’s energy that reaches the Earth, so it’s important to harvest this, for maximum efficiency.

But now, the new technique is able to address this, through the creation of spectrally tuned, solution-processed plasmonic nanoparticles. These modified particles allow for a greatly increased degree of control over light’s “propagation and absorption.”

“The new technique developed by Ted Sargent’s group shows a possible 35 per cent increase in the technology’s efficiency in the near-infrared spectral region,” states co-author Dr. Susanna Thon. “Overall, this could translate to an 11 per cent solar power conversion efficiency increase, making quantum dot photovoltaics even more attractive as an alternative to current solar cell technologies.”

“There are two advantages to colloidal quantum dots,” Thon says. “First, they’re much cheaper, so they reduce the cost of electricity generation measured in cost per watt of power. But the main advantage is that by simply changing the size of the quantum dot, you can change its light-absorption spectrum. Changing the size is very easy, and this size-tunability is a property shared by plasmonic materials: by changing the size of the plasmonic particles, we were able to overlap the absorption and scattering spectra of these two key classes of nanomaterials.”

The technique is based around the use of gold nanoshells embedded directly into the quantum dot absorber film. Gold isn’t cheap, though, so the researchers are currently working to find cheaper metals to replace gold, something that they say shouldn’t be difficult.

The new research paper, titled “Jointly-tuned plasmonic-excitonic photovoltaics using nanoshells,” was just published in the journal Nano Letters.

Source: University of Toronto Faculty of Applied Science and Engineering
Image Credit: University of Toronto

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