Strong interlayer coupling in two-dimensional PbSe with high thermoelectric performance

TL;DR

This study reveals strong interlayer coupling in two-dimensional PbSe, which enhances thermoelectric performance by reducing thermal conductivity without significantly affecting electronic transport, achieving a high ZT of 2.5 at 900 K.

Contribution

It uncovers strong covalent-like interlayer coupling in PbSe, challenging the assumption of weak van der Waals interactions in layered materials.

Findings

Maximum ZT of 2.5 at 900 K for p-type PbSe

Strong interlayer coupling reduces phonon thermal conductivity

Electronic transport slightly affected by interlayer tuning

Abstract

It was generally assumed that weak van der Waals interactions exist between neighboring layers in the two-dimensional group-IV chalcogenides. Using PbSe as a prototypal example, however, we find additional strong coupling between the Pb-Pb layers, as evidenced by detailed analysis of the differential charge density. The coupling resembles covalent-like bond and exhibits strong harmonicity around the equilibrium distance, which can be fine tuned to obviously reduce the phonon thermal conductivity but slightly change the electronic transport of PbSe. As a consequence, a maximum ZT value of 2.5 can be realized at 900 K for the p-type system. Our work offers an effective and feasible design strategy to enhance the thermoelectric performance of similar layered structures.