福利姬自慰

Ted Sargent, a global leader in the field of solar cell technology, is co-author of the paper "Jointly-tuned plasmonic-excitonic photovoltaics using nanoshells

New technique makes solar cells more efficient

Improving colloidal quantum dots

A new technique developed by University of Toronto Engineering Professor Ted Sargent and his research group could lead to significantly more efficient solar cells.

In a paper published in the journal Nano Letters, the group describes a new technique to improve efficiency in what are called colloidal quantum dot photovoltaics. It's a technology that already promises inexpensive and more efficient solar cell technology.

But researchers say such devices could be even more effective if they could better harness the infrared portion of the sun鈥檚 spectrum, which is responsible for half of the sun鈥檚 power that reaches the Earth.

The solution has an unwieldy name: spectrally tuned, solution-processed plasmonic nanoparticles. These particles, researchers say, provide unprecedented control over 濒颈驳丑迟鈥檚 propagation and absorption.

The new technique developed by Sargent鈥檚 group shows a possible 35 per cent increase in the technology鈥檚 efficiency in the near-infrared spectral region, says co-author Susanna Thon (pictured left). Overall, this could translate to an 11 per cent solar power conversion efficiency increase, she says, making quantum dot photovoltaics even more attractive as an alternative to current solar cell technologies.

鈥淭here are two advantages to colloidal quantum dots,鈥 Thon says. 鈥淔irst, they鈥檙e 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 苍补苍辞尘补迟别谤颈补濒蝉.鈥

Sargent鈥檚 group achieved the increased efficiency by embedding gold nanoshells directly into the quantum dot absorber film. Gold is not usually thought of as an economical material but researchers say lower-cost metals can be used to implement the same concept proved by Thon and her co-workers.

The current research provides a proof of principle, says Thon.

鈥淧eople have tried to do similar work but the problem has always been that the metal they use also absorbs some light and doesn't contribute to the photocurrent - so it's just lost light.鈥

More work needs to be done, she adds.

鈥淲e want to achieve more optimization, and we鈥檙e also interested in looking at cheaper metals to build a better cell. We鈥檇 also like to better target where photons are absorbed in the cell 鈥 this is important photovoltaics because you want to absorb as many photons as you can as close to the charge collecting electrode as you possibly can.鈥

The research is also important because it shows the potential of tuning nanomaterial properties to achieve a certain goal, says Paul Weiss, Director of the California NanoSystems Institute at the University of California, Los Angeles (UCLA).

"This work is a great example of fulfilling the promise of nanoscience and nanotechnology,鈥 Weiss says. 鈥淏y developing the means to tune the properties of nanomaterials, Sargent and his co-workers have been able to make significant improvements in an important device function, namely capturing a broader range of the solar spectrum more effectively.鈥

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