Computational prediction of high thermoelectric performance in As$_{2}$Se$_{3}$ by engineering out-of-equilibrium defects

TL;DR

This study uses first-principles calculations to explore how engineering out-of-equilibrium defects in As₂Se₃ can significantly enhance its thermoelectric performance, achieving high figures of merit.

Contribution

It demonstrates that controlling defect concentrations can substantially improve thermoelectric efficiency in As₂Se₃, providing a pathway for optimizing thermoelectric materials.

Findings

High thermoelectric figures of merit (ZT) of 3 for p-type and 2 for n-type achieved with increased relaxation times.

Equilibrium antisite defect concentration estimated at about 10^14 cm^-3, much lower than experimental levels.

Defect engineering could potentially reduce defect concentrations, enhancing thermoelectric properties.

Abstract

We employed first-principles calculations to investigate the thermoelectric transport properties of the compound As$_2$Se$_3$. Early experiments and calculations have indicated that these properties are controlled by a kind of native defect called antisites. Our calculations using the linearized Boltzmann transport equation within the relaxation time approximation show good agreement with the experiments for defect concentrations of the order of 10$^{19}$ cm$^{-3}$. Based on our total energy calculations, we estimated the equilibrium concentration of antisite defects to be about 10$^{14}$ cm$^{-3}$. These results suggest that the large concentration of defects in the experiments is due to kinetic and/or off-stoichiometry effects and in principle it could be lowered, yielding relaxation times similar to those found in other chalcogenide compounds. In this case, for relaxation time higher than 10 fs, we obtained high thermoelectric figures of merit of 3 for the p-type material and 2 for the n-type one.