EAGER: Development of a rectenna for energy harvesting and detection applications

University Of South Florida, Tampa FL

Investigators

Abstract

Growing interest in the utilization of solar energy has significantly stimulated research in the field of photovoltaics, although most PV devices are still limited to maximum conversion efficiencies of about 20% to 30%. The power conversion efficiency of a rectenna, in contrast to most other energy harvesting devices, has been found to be greater than 85% at 2.45GHz. A rectenna is basically an antenna that captures electromagnetic radiation and converts it to direct current (DC) through a rectifier (diode). Because of the lack of diodes that can rectify at high solar radiation frequencies in the visible and near infra-red (IR) range, a more practical rectenna can be designed that first captures the solar radiation and then converts it to IR in the ~30 THz range using an innovative frequency selective emitter. Once the energy has been downscaled to ~30THz frequency range, it can be rectified using diodes that operate using the quantum tunneling mechanism. The rectification property of metal-insulator-metal (MIM/MIIM) diodes could be used in energy conversion devices or detectors, where the detectors use external circuits to amplify the rectified signal and the energy harvesters use the rectified signal as usable power. Upon the successful demonstration of a working rectenna and because of inexpensive and widely available materials needed for the roll-to-roll manufacturing of rectennas, very high efficiency and low cost (few cents per watt) rectenna solar modules would be achievable. This research project addresses the two major scientific obstacles preventing the development of a working rectenna at the THz frequency range: (a) Plasmonic emitters will be designed to selectively emit radiation centered around the working frequency of the antenna (~30THz). Carefully chosen dimensions of periodic gratings and suitable materials will be used to design an emitter to selectively emit around the frequency of interest. (b) Tunnel diodes with MIM/MIIM configurations will be fabricated to rectify the radiation captured by the nanoantenna. The deposition of a conformal monolayer of uniform and pinhole free insulator(s) onto the bottom metal surface is required for a successful diode. In addition, a diode will be developed that can have a higher degree of asymmetry, sensitivity and sharp turn-on voltage. Resonant tunneling diodes with multiple insulating layers can exhibit nonlinear and asymmetric I-V characteristics which makes them well suited for rectification purposes at high frequencies. Such MIM/MIIM diodes will have THz switching capability while maintaining low resistance to match the antenna impedance. An array of nanoantennas and fabricated rectifiers can be used in energy harvesting and detection applications. The program will integrate research and education and promote teaching, training and learning at all levels for rectenna applications in energy harvesting and detectors.