Rectennas, is in layman’s terms, a device that’s part antenna, part rectifier diode. It uses the qualities of both antenna & diode to convert light into a direct electrical current. Although originally developed in the 1960s and 1970s, researchers have been working for more than 40 years to make these devices work at Optical Wavelengths.
Taking all that hard work to fruition, engineers at the Georgia Institute of Technology have developed the World’s First Optical Rectenna‘s using Multiwall Carbon Nanotubes & Tiny Rectifiers. The carbon nanotubes act as antennas to capture light from the sun or other sources.
When the device is operational, it’s design allows light to pass through the transparent calcium-aluminum electrode & interact with the nanotubes. The metal-insulator-metal junctions at the nanotube tips serve as rectifiers, switching on and off, allowing electrons generated by the antenna to flow one way into the top electrode. This process works extremely fast, at femtosecond intervals to produce this output.
The researchers hope that by placing billions of such rectennas in an array & boosting them through optimization techniques, would produce significant current output. They could potentially provide a new technology for Photodetectors that would operate without the need for cooling & Energy Harvesters that would convert waste heat to electricity.
“We could ultimately make solar cells that are twice as efficient at a cost that is ten times lower, and that is to me an opportunity to change the world in a very big way” said Baratunde Cola, from Georgia Tech. “As a robust, high-temperature detector, these rectennas could be a completely disruptive technology if we can get to one percent efficiency. If we can get to higher efficiencies, we could apply it to energy conversion technologies and solar energy capture.”
This research is supported by the Defense Advanced Research Projects Agency (DARPA), the Space and Naval Warfare (SPAWAR) Systems Center and the Army Research Office (ARO). It has also been published on September 28 in the reputed journal, Nature Nanotechnology.
So far this technology is highly experimental. It will take almost an year for this technology to reach commercial potential. But once it does, these optical rectennas would open up many possibilities for efficient energy capturing.