Nanoantenna Thermocouples for Energy Harvesting

This talk focuses on energy harvesting in the long-wave regime of the solar spectrum, which cannot be exploited by solar cells due to band gap limitations of photovoltaics. An alternative physical mechanism based on the wave nature of electromagnetic radiation will be discussed, particularly with reference to novel devices that combine thermocouples with nanometer-scale antennas for the long-wave infrared regime. Like radio antennas, these capture electromagnetic waves, but to capture infrared radiation at micron-scale wavelengths they need to be engineered on the nanometer scale. This radiation induces electrical currents in the antennas, leading to local heating effects that can be harvested in nano-scale thermocouples. For efficient energy harvesting, the hot junction of the thermocouple has to be placed at the feed point of the nanoantenna, where the heating effect is strongest. Several thermocouples can be placed in series to form a thermopile, thus maximizing the amount of energy harvested.

We will discuss several different nanoantenna-nanothermocouple arrangements, focusing on our recent discovery that thermocouples can be realized by a single metal. In conventional thermocouples, the difference in the Seebeck coefficient depends on the use of two different metals; in ours, the difference is provided by shape-engineering of the junction.  The use of single-metal thermocouples significantly reduces the complexity of fabrication and opens the possibility of large-scale arrays for infrared energy harvesting applications. We will explore in detail the possibility of manufacturing such large-scale arrays of nanoantenna-coupled thermocouples using nanoimprinting and nanotransfer fabrication technologies.