The blackest black for more efficient solar cells

Sep 19, 2019 10:47 PM ET
  • MIT scientists claim to have created a material 10 times more black than anything witnessed to date. It is said to be able to absorb more than 99.96% of incoming light and reflect 10 times less light than other superblack materials. The invention may be interesting for the development of black silicon PV technology and carbon nanotube-based solar cells.
The blackest black for more efficient solar cells
Image: Natcore
Scientists from MIT have developed a material made of vertically aligned carbon nanotubes which they claim is the blackest on record.
According to the findings of a study published in ACS-Applied Materials and Interfaces, the patented carbon nanotube technology (CNT) is able to absorb more than 99.96% of light.
“Any object covered with this CNT material loses all its plasticity and appears entirely flat, abbreviated/reduced to a black silhouette,” said the foil’s creator, MIT scientist Brian Wardle. “Our material is 10 times blacker than anything that’s ever been reported but I think the blackest black is a constantly moving target. Someone will find a blacker material and eventually we’ll understand all the underlying mechanisms and will be able to properly engineer the ultimate black.”
If the claim is true, the new material will better Vantablack, which was developed with a low-temperature carbon nanotube growth process and is being studied for potential application in the manufacture of solar cells more efficient at entrapping light. Vantablack was developed by U.K. business Surrey NanoSystems and is able to absorb up to 99.96% of light.
The MIT researchers, who previously worked on how to improve the electrical and thermal properties of carbon nanotubes on electrically conducting materials such as aluminum, said the material could be applied to reduce unwanted glare in optical blinders or to help space telescopes spot orbiting exoplanets.
Solar potential
Professor Wardle told pv magazine the new material could also have a solar power application. “Yes, this is one of the application areas that we identified as most promising for the CNTs on aluminum, due to the direct connection between the CNTs and the metallic aluminum, i.e. there is no alumina layer in between that limits electrical and thermal transport from the CNTs to/from the aluminum,” he said.
The MIT research team has not explored use of the material in black silicon technologies or CNT-based solar cells to date, however.
Long neglected by the industry, interest in black silicon processes has recently emerged with the adoption of diamond wire sawing with big manufacturers including Canadian Solar, GCL Systems Integration and Suntech exploring the technology.
Featuring nanostructures etched on its surface, black silicon makes possible the production of solar cells with a larger surface area and the ability to absorb light at wider angles. Conventional solar cells entrap indirect photons, with lower efficiency. Black silicon is also more efficient at absorbing shorter wavelengths of light.