Research Advances Commercial Applications of Optical Rectennas

Research to develop technologies for efficiently harvesting wireless energies consisting of electromagnetic waves are gaining increasing significance in the power and energy industry. Rectennas which combine the characteristics of rectifiers and antennas can be promising methods to convert waste heat to electricity for powering special applications. However, current methods to commercially harvest wireless energy, such as from the solar energy are absent. Researchers at the Georgia Institute of Technology working with optical rectenna, first developed in 2015, designed technology improvements for increasing the efficiency of devices in which antennas are used. Their work could hold profound potential for developing technologies for a wide spectrum of next-generation energy harvesting applications and inexpensively capturing solar energy.

The work is supported by the National Science Foundation and the United States Army Research Laboratory under the Young Investigator Program. The work is published online on January 26, 2018 in the journal Advanced Electronic Materials.

Multiwall Carbon Nanotubes with Rectifier Diodes Bring Design Improvements

Used as a part of wireless energy transmission systems, these special antennas are proving promising for converting electromagnetic energy into direct current electricity, with the help of rectifying diodes and special filters. The researchers engineered a series of multiwall carbon nanotubes in the optical rectenna and fabricated them onto matching rectifier diodes with the help of advanced nanoscale techniques.

Combination Coating for Nanotube-Diode Junction Imperative for Large Current Flow

The team conducted comprehensive tests to test the design in a number of devices. One of the key challenges they faced was with the use of calcium for maximizing electron capture so that, practically, for creating substantial current flow with minimal resistance by antenna-diode junction. To this end, they tinkered with several combinations of apt coating for the carbon nanotube-diode junction and found alumina (Al2O3) and hafnium dioxide (HfO2) to be useful. This, they demonstrated could ease the operation and make the fabrication process pragmatic.

These design improvements could make the rectennas commercially useful for a variety of energy harvesting devices since they up the efficiency by two times. In particular, this can be key determinant for inexpensive low-power devices including sensors and photodetectors, expanding the potential of Internet of Things devices and could prove useful for powering space crafts, notably to Mars.