Limit of zT enhancement in rock-salt structured chalcogenides by band convergence?

TL;DR

This study numerically investigates how band convergence affects thermoelectric performance in rock-salt chalcogenides, revealing that while it can boost power factor, it also increases thermal conductivity, limiting ZT enhancement.

Contribution

The paper provides a comprehensive numerical analysis of band convergence effects on thermoelectric properties in rock-salt chalcogenides, highlighting the trade-offs involved.

Findings

Extra valence band enhances power factor

Band convergence increases electronic thermal conductivity

Predicted maximum ZT values for PbTe, PbSe, SnTe

Abstract

Rock-salt structured chalcogenides, such as PbTe, PbSe, and SnTe, are the top candidates for mid-temperature thermoelectric applications, and their p-type thermoelectric efficiencies can be enhanced via aligning the valence bands. Here, we provided comprehensive numerical investigations on the effects of band convergence on electronic properties. We found that the extra valance band can indeed significantly enhance the power factor. Nevertheless, the extra valance band can also increase the electronic thermal conductivity, which partially offsets the enhanced power factor for the overall figure-of-merit. Finally, we predicted that the maximum figure-of-merit for PbTe, PbSe, and SnTe can reach to 2.2, 1.8, and 1.6, re-spectively, without relying on the reduction in lattice thermal conductivity.