Hierarchical structures for high-performance chalcogenides: From tellurides to sulfides

Abstract

An efficient way to enhance the performance of thermoelectric materials is to tune its structure at all length scales from atomic to microscopic. This review addresses recent developments in all-length-scale hierarchical structuring of the thermoelectric chalcogenides, including PbTe, mineral-based sulfides, and layered sulfides. The inclusion of nanostructures in PbTe significantly reduces the lattice thermal conductivity without affecting the charge carrier mobility, leading to very high thermoelectric figure of merit ZT. The high efficiency in the nanostructured PbTe-based devices was demonstrated. For mineral-based sulfides, the low-energy atomic vibration inhibits heat flow, resulting in a low lattice thermal conductivity and high ZT. In layered sulfides, the lattice thermal conductivity is reduced through the intercalation of guest atoms/layers into host crystal layers which effectively scatters heat-carrying phonons. Furthermore, the highly oriented microtexture of layered systems allows high carrier mobility in the in-plane direction, leading to a high thermoelectric power factor. Among all chalcogenides, sulfides could pave the way for environment-friendly and cost-effective thermoelectric systems.