Oxychalcogenides as Thermoelectric Materials: An Overview

Thermoelectric materials, which can convert heat into electricity and vice versa, have essential applications in power generation, thermocouples, sensors, and cooling. In the past decade, a lot of research has been devoted to developing various oxide-based thermoelectric materials, for mid- to high-temperature applications, ensuring robustness, long lifetimes, and low production costs. Among these oxide materials, one popular class is oxychalcogenides. A comprehensive discussion on the structural, electronic, and thermoelectric properties of both p-type and n-type oxychalcogenides is presented in this review article. The alternatively stacked conducting and insulating layers in these oxychalcogenides combined with a unique bonding network lead to interesting electronic properties and intrinsically low thermal conductivity. The article focuses primarily on Bi-based oxychalcogenides which have shown relatively good thermoelectric performance in the mid- to high-temperature range, with an elaborate discussion on n-type compositions. Several approaches such as chemical doping, modulation doping, introducing vacancies, band structure engineering, and so forth are summarized, vastly improving the zT in these materials and enabling their potential viability for thermoelectric applications. Finally, we discuss a few strategies as a future direction to further enhance the thermoelectric performance in these oxychalcogenide materials.