SAN FRANCISCO—Researchers at the University of Surrey in the U.K. have developed nanometer-thin graphene sheets that can better absorb light and heat. Traditionally a poor absorber of light, the sheets could power smart wallpaper or other applications in the Internet of Things.
A team at Surrey’s Advanced Technology Institute (ATI) employed nanotexturing, a technique involves growing graphene around a textured metallic surface, to make the sheets.
The sheets are 90% more light absorbent than traditional graphene, largely due to nano-patterning to localizes light into the narrow spaces between the textured surface.
Flexible solar cell. Source: University of Surrey
“Nanotexturing graphene has the effect of channeling the light into the narrow spaces between nanostructures, thereby enhancing the amount of light absorbed by the material,” wrote Dr. José Anguita, the study’s lead author. “Typically a graphene sheet would have 2-3% light absorption. Using this method, our ultrathin coating of nanotextured few-layer graphene absorbs 95% of incident light across a broad spectrum, from the UV to the infrared.”
The nano patterns on the graphene sheets resemble moths’ eyes, which have microscopic patterning that allows them to see in dim conditions.
"These work by channelling [sic] light towards the middle of the eye, with the added benefit of eliminating reflections, which would otherwise alert predators of their location,” wrote ATI Head, Professor Ravi Silva.
ATI researchers reported their findings in the journal Science Advances, adding:
We demonstrate the utility of our approach to produce the blackbody absorber on delicate opto-microelectromechanical infrared emitters, using a low-temperature, noncontact fabrication method, which is also large-area compatible. This development may pave a way to new fabrication methodologies for optical devices requiring light management at the nanoscale.
Solar cells could be coated with these thin graphene sheets to harvest very dim light or be installed indoors to generate electricity from light or heat to power smart home applications. Silva added that IoT sensors and energy harvesters could also benefit from this kind of coating.
“We are very excited about the potential to exploit this material in existing optical devices for performance enhancement, whilst looking towards new applications,” Silva wrote, adding that Surrey’s Graphene Centre is looking for partners to develop new technologies.
The moths’ eye technology was developed in cooperation with BAE Systems for infrared imaging in opto-MEMs devices.
— Jessica Lipsky, Associate Editor, EE Times