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Most sunlight striking the Earth is absorbed by its surfaces, oceans and atmosphere. As a result of this warming, infrared radiation is emitted constantly all around us—estimated to be millions of gigawatts per second. A KAUST team has now developed a device that can tap into this energy, as well as waste heat from industrial processes, by transforming quadrillionth-of-a-second wave signals into useful electricity.

Unlike solar panels that are limited by daylight hours and weather conditions, infrared heat can be harvested 24 hours a day. One way to achieve this is to treat waste or infrared heat as high-frequency electromagnetic waves. Using appropriately designed antennas, collected waves are sent to a rectifier, typically a semiconductor diode, that converts alternating signals to direct current charge for batteries or power devices.

Putting these ‘rectenna’ designs into practice has been difficult. Because infrared emissions have very small wavelengths, they need micro- or nanoscale antennas that are not easy to fabricate or test. Additionally, infrared waves oscillate thousands of times faster than a typical semiconductor can move electrons through its junction. “There is no commercial diode in the world that can operate at such high frequency,” says Atif Shamim, project leader from KAUST. “That’s why we turned to quantum tunneling.”

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