Nanocones: Increased Solar Efficiency, Lower Costs

nanocones Nanocones: Increased Solar Efficiency, Lower Costs

Researchers at the Oak Ridge National Laboratory have developed anew, three-dimensional photovoltaic technology using minuscule devicescalled nanocones to convert sunlight into electricity. The nanoconeshave increased the conversion efficiency of photovoltaics by 80 percentin lab testing.

A lot of attention in the solar world these days is on photovoltaics with carbon nanotubes, like recent research from MIT using viruses to arrange and coat nanotubes.

But Dr. Jun Xu, Ph.D., and his team in the Oak Ridge’s ChemicalSciences Division, including Sang Hyun Lee, have developed nanoconesmade of zinc oxide that increase the efficiency of photovoltaics.

“It does not use nanotubes. It uses zinc oxide cones. Our efficiencyis among the highest [in nanostructure photovoltaics]. That’s what we’re excited about,” Xu said.

The research was focused on cadmium telluride-based photovoltaics.

“The material is not new. But the structure is,” he said. “It is acombination of zinc oxide [nanocones] and cadmium telluride [film].”

The nanocones conduct electrons produced by the cadmium telluride, which absorbs photons.

The cones allow the photovoltaic device to create an electric fielddistribution that efficiently transports the charge generated by thedevice. The field minimizes trapping of photo-generated charges, Xusaid.

“The cone allows a greater yield of charge collection, because thefield can drive minority carriers—electrons—moving to their electrode,”he said.

The team was able to boost the performance of the light-to-powerconversion efficiency from 1.8 percent in a flat surface of the samematerials to 3.2 percent using the nanocones, according to Oak Ridge, an efficiency increase of 80 percent.

Since the technology increases the efficient charge transport, thephotovoltaic device could also tolerate defective materials, the labsaid, helping it to reduce the costs of fabrication.

The technology is still not ready for the commercial market, but the material shouldn’t be too expensive to make.

The nanocones are also self-assembling, according to Xu.

“That’s why there’s the potential to save the costs on manufacturing,” he said.

But Xu estimated that the device would not be ready for the commercial market for another four or five years.

Image courtesy of the Oak Ridge National Laboratory.