First optical rectenna that converts light to DC current

Washington: A team of engineers, including Indian-origin researchers, has demonstrated the world's first optical rectenna - a device that combines the functions of an antenna and a rectifier diode to convert light directly into DC current.

The optical rectennas can provide a new technology for photodetectors that would operate without the need for cooling, energy harvesters that would convert waste heat to electricity and ultimately a new way to efficiently capture solar energy.

Baratunde Cola, associate professor at Georgia Institute of Technology and collaborators Asha Sharma, Virendra Singh and Thomas Bougher constructed devices that utilize the wave nature of light rather than its particle nature.

They used a long series of tests -- and more than a thousand devices -- to verify measurements of both current and voltage to confirm the existence of rectenna functions that had been predicted theoretically so far.

The devices operated at a range of temperatures from five to 77 degrees Celsius.

In the new devices, the carbon nanotubes act as antennas to capture light from the sun or other sources.

As the waves of light hit the nanotube antennas, they create an oscillating charge that moves through rectifier devices attached to them.

The rectifiers switch on and off at record high petahertz speeds, creating a small direct current.

"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 Cola.

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,” he mentioned.

The research appeared in the journal Nature Nanotechnology.