Butterfly eye became a model for graphene rectenes with record light absorption

A group of scientists from the University of Surrey (UK) announced the creation of 2D material with record levels. A multilayer graphene film with a rectene structure absorbs light in 99% of the range from mid-infrared to ultraviolet. If such a film is used in solar panels, then it is possible to generate electricity even in diffused light reflected from walls or from the glow of home appliances. That is, solar panels will work indoors. This can not even be called "batteries" when the film is applied to the surface of walls and other objects. (Another question is that the room will then remain almost in pitch darkness even on a sunny day)

Instead of the phrase "solar battery" in this case, it is better to talk about a "light-absorbing surface."

“The ability to design thin two-dimensional surfaces for absorbing light in a wide range is key in a large and ever-growing number of applications, including energy, optoelectronics and spectroscopy,” the material developers write in an abstract of their scientific work . “Although light absorption in a wide range is possible in high structures of carbon nanotubes about a millimeter high, it has not yet been possible to achieve such a result in nanometer structures.”



The invisible light-absorbing film that generates current will be used in numerous Internet of things devices, smart clothes, wearable electronics, smart wallpapers, household appliances, etc.

One of the authors of the scientific work, Professor Ravi Silva, explains, that in some insects (butterflies, moths, etc.) the eye is arranged according to completely different principles. Nanotechnology is used there, that is, nanostructured surfaces. On such a scale, these elements work as rectenes (rectifying antennas), that is, they directly convert the energy of the field of the incident wave into DC energy. The interaction of a wavelength of 4 μm with a metal nanoantenna is shown in the illustration.



In the inset in Figure B below, a comparison is made of the surface of the material with the eye of the butterfly Bicyclus anynana. Figure D shows the reflectivity of the created material (black graph).



“For years, people have been looking for applications of graphene that could be ubiquitous,” says Silva. - We are finally approaching the point where such applications begin to appear. We did what was previously considered impossible: we optimized the incredible optical properties of graphene. ”