Nano-cones could help neutralize manufacturing defects in solar cells

A new advance in solar cells that tips the surface with minuscule cone structures could neutralize manufacturing defects, boosting efficiency up to 80 percent.

In conventional solar panels, more than 50 percent of the charges generated by sunlight are lost due to defects, said Jun Xu, a researcher at the Department of Energy's Oak Ridge National Laboratory. The irregularities in the formation of the crystalline structure of solar cells can trap electrons and limit the transfer of sunlight to electrical energy.


 SOLAR FLAWS: Manufacturing defects impair solar cells ability to turn sunlight into electricity, but a new technique might help minimize the flaws. Image: Stephan Kambor via Wikimedia Commons

This is why Xu and his team are looking at how nanocones -- cone-shaped structures one-millionth of a meter long -- can neutralize the burden of defects.

The negative-polarity nanocones are made of zinc oxide, and surrounded by a positive-polarity cadmium telluride semiconductor that absorbs sunlight. The three-dimensional cone structure acts as a junction between the zinc oxide and cadmium telluride, making for a smoother conversion of the solar charge to electricity.

The idea, said Xu, is not to "fix" the defects, but to make them irrelevant. With the nanocone structure, the team was able to increase the overall electric charge to overcome the pitfalls of defects.
"If [manufacturers] make a defect with no way to solve it, we make the defect less relevant," he said. "You need to increase the efficiency ... you need to be able to increase change of transport. With a nanocone structure, you can do that."

On a small level, the efficiency gains are relatively minor -- rising to 3.2 percent, compared to 1.8 percent for panels without the nanocones. But Xu believes this will pay off on a larger scale.
"Our efficiency is moderate in generation, but the difference between the two platforms is huge," he said, referring to the models with and without nanocones. In the real world, even a much smaller percentage increase would be an important achievement for solar.

"If we can reduce the defective material, and we can increase the efficiency about 15 or 10 percent," he said, "that would be a huge success."

Zinc oxide and cadmium telluride serve as relatively cheap materials to create nanocones, as well, said Xu, with the potential to reduce the cost of commercial solar panels if applied to silicon -- the most common material used for solar panels.

The research will be published in the Institute of Electrical and Electronics Engineers' IEEE Proceedings.

From Climatewire with permission from Environment & Energy Publishing, LLC. www.eenews.net, 202-628-6500