Optical Rectennas Based on Nanowires

Challenge: While solar radiation is an abundant energy source current methods for its capture and use suffer from low efficiencies and high costs. For example conventional photovoltaic devices are limited to a theoretical maximum efficiency of 32%. Rectennas have received recent attention as energy harvesting and conversion devices. These devices absorb incident radiation and convert it to electricity through the use of a diode (rectifier). Although such devices have achieved over 90% conversion efficiency at microwave frequencies the fabrication of rectennas that operate in the optical frequency range is complicated by size limitations and the low frequency responses of planar diodes. As a result methods for the development of optical rectennas are desired. Solution: Nanowires behave as optical antennas and can be used in the fabrication of antenna arrays. The present invention contemplates the use of metallic nanowires as optical antennas in which the rectifying barrier is generated from a self-assembled monolayer of polar molecules. This strategy will provide the requisite switching frequencies for the use of these optical rectennas in solar cell applications. The use of nanowires with radii between 10-50 nm will offer lower capacitance for increased frequency response of the diode. Nanowires of these dimensions will also generate sufficient voltages from the incident solar radiation for use in photovoltaic applications. Development and Licensing Status: This technology is available for licensing from Rice University. A proof of principle experiment established the generation of a rectified photocurrent using carbon nanotubes coated with a self-assembled monolayer of dipolar molecules. Patent Status: A U.S. patent application has been filed for this technology (PCT publication no. WO2009/023778).