Rectifying antennas, or rectennas, were developed over 40 years ago and were used to intercept so-called spurious radiation, which was then converted into electrical energy. However, in view of their low efficiency, they had to be abandoned. Everything changed with the advent of carbon nanotubes.
A group of Georgia Tech engineers have developed modern rectennas that have the ability to capture light and convert it into direct current. This is made possible by using an array of billions of vertical carbon nanotubes on top of a silicon substrate formed by chemical vapor deposition.
Each of the nanotubes is a glazed aluminum oxide insulator, and the entire array is bounded by optically transparent layers of aluminum and calcium, which act as an anode. As a result of complex processes, a charge arises, which, passing through the built-in rectifiers, converts alternating current into direct current.
So far, a team of engineers led by Baratunde Cola has managed to create a device with an efficiency of only 1%. However, scientists are optimistic and confident that this is far from the limit and over time it will be possible to reach significantly higher rates, thus increasing the efficiency of solar panels at least twice.