Development of Cu<sub>2</sub>Se/Ag<sub>2</sub>(S,Se)-Based Monolithic Thermoelectric Generators for Low-Grade Waste Heat Energy Harvesting
Artoni Kevin R. Ang, Itsuki Yamazaki, Keisuke Hirata, Saurabh Singh, Masaharu Matsunami, Tsunehiro Takeuchi
Abstract
With the ongoing climate and energy crises, thermoelectric conversion has slowly emerged as a clean and reliable alternative energy source for small Internet of Things (IoT) devices. Commercially available thermoelectric generators (TEGs) are typically composed of expensive and toxic Bi 2 Te 3 -based thermoelectric materials and require complicated and energy-intensive device assembly processes. As an alternative solution, we have developed a Ag- and Cu-chalcogenide-based monolithic TEG using simple, quick, and low-energy-cost device fabrication processes for low-grade waste heat recovery for energy harvesting. We used ductile Ag 2 S 0.55 Se 0.45 and overstoichiometric Cu 2.075 Se, both possessing excellent transport properties around room temperature, with a zT value of ∼0.5 at 300 K. By optimizing the device fabrication process, we were successfully able to assemble the monolithic TEGs without any significant Ag- or Cu-ion migration and obtained a dense and robust device. Strategic optimization of the device structure was able to reduce the electrical contact resistance of the device, which resulted in increased power output. A maximum power density of 0.68 mW/cm 2 at a Δ T = 30 K was obtained, which is comparable to a similar Bi 2 Te 3 -based monolithic TEG. These results show the potential of chalcogenide-based monolithic TEG as a simple and low-cost alternative to Bi 2 Te 3 -based TEGs for energy harvesting applications.