Prediction of higher thermoelectric performance in BiOCuSe by weakening electron-polar optical phonon scattering

Abstract

<jats:title>Abstract</jats:title> <jats:p>BiOCuSe is a promising thermoelectric material, but its applications are hindered by low carrier mobility. We use first principles calculations to analyse electron-phonon scattering mechanisms and evaluate their contributions to the thermoelectric figure of merit <jats:italic>ZT</jats:italic>. The combined scattering of carriers by polar optical (PO) and longitudinal acoustic (LA) phonons yields an intrinsic hole mobility of 32 cm<jats:sup>2</jats:sup> V<jats:sup>-1</jats:sup> s<jats:sup>-1</jats:sup> at room temperature and a temperature power law of <jats:italic>T</jats:italic><jats:sup>-1.5</jats:sup>, which agree well with experiments. We demonstrate that electron phonon scattering in the Cu-Se layer dominates at low <jats:italic>T</jats:italic>, while contributions from the Bi-O layer become increasingly significant at higher <jats:italic>T</jats:italic>. At room temperature, <jats:italic>ZT</jats:italic> is calculated to be 0.48 and can be improved by 30% through weakening PO phonon scattering in the Cu-Se layer. This finding agrees with the experimental observation that weakening the carrier-phonon interaction by Te substitution in the Cu-Se layer improves mobility and <jats:italic>ZT</jats:italic>. At high <jats:italic>T</jats:italic>, the figure of merit is improved by weakening phonon scattering in the Bi-O layer instead. The theoretical <jats:italic>ZT</jats:italic> limit of BiOCuSe is calculated to be 2.5 at 875 K.</jats:p>