MIT engineers new tech to improve solar efficiency

Researchers at MIT developed a new technology using carbon nanotubes to harvest multiple wavelengths of sunlight and concentrate it. By concentrating sunlight, these nano antenna can concentrate sunlight up to 100 times, according to MIT. The research has produced “a structure that can absorb a very broad band of the solar spectrum,” Michael Strano, associate professor of chemical engineering and research team leader, told Clean Energy Authority.

Such nano antennas could drastically improve the efficiency of photovoltaics, allowing for significantly more PV electric production in a smaller space.

Strano envisioned one application where the antennas could be applied as concentrating coating for PV cells to increase their effectiveness.

He said the technology could lead to coatings that could “help funnel more light into these devices.” Current solar concentrators use reflectors to concentrate infrared heat on one area, superheating a surface to produce electricity, or they use lenses to focus sunlight onto a PV cell, increasing its efficiency.

The antennas take advantage of “new nanomaterials, that are arranged in a way that can turn them into optical concentrators,” Strano said. As sunlight strikes this material subatomic excitons (energy formed by excited electrons in crystal and an associated hole) move from the outside of the material to the inside, where they’re concentrated, MIT explained.

The researchers “have not yet built a photovoltaic device using the antenna, but they plan to,” MIT said. In such a device, an antenna would surround a semiconducting core, concentrating photons “before the PV cell converts them to an electrical current,” according to the institute.

“Recent breakthroughs had to happen to even make these materials” possible, Strano added. He explained that they can be applied across a wide range of light-based technologies. Ultimately, “It gives scientists and engineers a new way to manipulate or control photons,” he said.

Strano told CEA, that as large manufacturers take to producing carbon-based nanomaterials, the cost of manufacturing such materials has fallen exponentially. Ultimately, production of carbon nanotube coating could become cheaper than the polymers now used to coat PV cells, he said.

The research was published in the online version of Natural Materials on Sept. 12. Postdoctoral associate Jae-Hee Han and graduate student Geraldine Paulus are lead authors of the research (both of them, in addition to Strano, are pictured above).