Outstanding thermoelectric performance predicted for out-of-plane p-doped GeSe

TL;DR

This study predicts that p-doped GeSe exhibits exceptional thermoelectric performance, especially out-of-plane, with high zT values at elevated temperatures, driven by its favorable electronic and thermal properties.

Contribution

The paper provides the first comprehensive first-principles prediction of thermoelectric properties of p-doped GeSe, highlighting its potential as a high-performance thermoelectric material.

Findings

Out-of-plane GeSe surpasses SnSe in thermoelectric performance above 500 K.

Predicted maximum zT of 3.2 at 900 K for optimal hole density.

GeSe exhibits high Seebeck coefficients and ultralow thermal conductivity.

Abstract

The record-breaking thermoelectric performance of tin selenide (SnSe) has motivated the investigation of analogue compounds with the same structure. A promising candidate that emerged recently is germanium selenide (GeSe). Here, using extensive first-principles calculations of the hole-phonon and hole-impurity scattering, we investigate the thermoelectric transport properties of the orthorhombic phase of p-doped GeSe. We predict outstanding thermoelectric performance for GeSe over a broad range of temperatures due to its high Seebeck coefficients, extremely low Lorenz numbers, ultralow total thermal conductivity, and relatively large band gap. In particular, the out-of-plane direction in GeSe presents equivalent or even higher performance than SnSe for temperatures above 500 K. By extending the analysis to 900 K, we obtained an ultrahigh value for the thermoelectric figure of merit (zT = 3.2) at the optimal hole density of 4x10^19 cm^-3. Our work provides strong motivation for continued experimental work focusing on improving the GeSe doping efficiency in order to achieve this optimal hole density.