SUMMARY

Carbon nanotubes (CNTs) have shown potential for applications in solar energy harvesting technologies. This dissertation will explore the unique use of CNTs to create an optical rectenna (‘rectifying antenna’), which is a burgeoning alternative to photovoltaic solar technologies. A rectenna incorporates two elements: an antenna that captures electromagnetic radiation, and a diode that rectifies the a.c. antenna oscillations into useable d.c. power. Realizing an optical-frequency rectenna requires an antenna that can efficiently capture optical radiation, and a diode that can operate at nearly PHz (1015 Hz) frequencies. This dissertation details an optical rectenna based on forests of CNTs. The CNTs act as an array of individual antennas that absorb the light. On the tips of each CNT, high speed tunneling diodes are fabricated to rectify the absorbed light into d.c. electricity. Prior to this work, the first optical rectenna was demonstrated in 2015; researchers used CNTs to obtain solar conversion efficiency up to 10-6 %. My work advances the original CNT rectenna design by improving the tunneling diode, which is responsible for the bulk of the low power production. I begin by studying the diode tunneling barrier. Modifying the tunneling geometry enhances electron conduction significantly to achieve a higher performing diode. I use the enhanced diode to show a 100-fold improvement in optical response and provide the first air-stable demonstration of solar rectification. Experiments are validated with simulations of rectenna theory, which also offers valuable estimations of efficiency limits to guide future improvements. Lastly, this work introduces a novel modification to the device design to incorporate polymer-based materials in conjunction with the CNT forest. This design is facile, scalable, and flexible, promising a commercially viable approach to efficient energy harvesting applications. Meeting URL: https://bluejeans.com/668928189