Scientists from the
The technology has caught the attention of local venture investors from the
Cottonwood acquired an option to license the invention from the
"It's still very early stage, but if the theoretical impact of this technology is shown to be real through further lab testing, then we think it has a lot of potential for market disruption," said Cottonwood managing partner
First Photonics expects to apply its technology to concentrating PV systems that use multi-junction solar cells. Unlike a single-cell rooftop PV, multi-junction systems contain various layers of cells where each junction, or subcell, captures and converts sunlight to electricity, increasing output.
Those systems also use massive reflectors, or mirrors, to concentrate solar rays. That immensely magnifies the amount of sunlight available for cell conversion, helping to produce industrial-scale electric generation.
Nevertheless, concentrating the sunlight also greatly increases the amount of heat striking the cells. That interferes with PV efficiency, thus limiting the level of solar concentration that designers can build into systems, said
"With any semiconductor, high operating temperatures will decrease performance levels," Balakrishnan said. "Designers need to concentrate sunlight to make large PV systems economically viable, but as the sun gets more and more concentrated, the systems heat up too much, limiting solar-cell performance."
Overheating also wears down PV materials over time, reducing the life of cells.
"Some concentrating systems are so hot they can melt a penny, so you end up with degradation of the solar crystals," Balakrishnan said.
To alleviate heating, Balakrishnan and his colleagues created an inexpensive way to attach CVD diamonds to the base of solar cells.
That synthetic material, which is made through a crystal-growing process, is one of the best thermal-grade conductors known to man, Balakrishnan said. It's being introduced fairly widely today in the semiconductor industry as a replacement for copper, traditionally used to conduct heat away from chips in things such as computers.
"CVD diamond is about four times better than copper as a thermal conductor," he said. "And the process of making the diamond is getting cheaper because production is scaling up as computer electronics developers start to use it widely. That's pushing prices down, making mass manufacturing of the material more economical."
The diamond almost instantaneously pulls heat away from cells and spreads it throughout the diamond's own surface. The heat then can be siphoned away from the diamond through heat sinks, such as fins like those in a car radiator that help radiate the heat out into the air.
By reducing the heat in concentrating multi-junction PV systems with an inexpensive CVD diamond-based material, designers not only can increase solar cell efficiency, they can increase concentration levels to produce more electricity, making the overall system more economical, Balakrishnan said.
The inventors developed the process over three to four years. Cottonwood now expects to prove the technology's viability in the next few months.
In fact, the
The technology is patented, with UNM and the
"We have a lot of jointly owned technology with the national labs and other research universities, but this is the first one that we're jointly commercializing with the
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