Cation disorder and bond anharmonicity synergistically boosts the thermoelectric performance of p-type AgSbSe2

Abstract

AgSbSe₂ is one of the important Te-free chalcogenides in I–V–VI₂ semiconductors, showing attractive functional properties and enhancing the thermoelectric performance. Here we report the thermoelectric performance of the polycrystalline p-type AgSbSe₂ nanostructured compound synthesized via a hydrothermal method followed by cold-press technique. In the as-prepared sample, the synergistic combination of low thermal conductivity (0.589 W m K⁻¹) and high-power factor (3.3 μW cm K⁻²) has been observed to successfully boost the thermoelectric figure of merit. The cubic phase structure and disordered lattice of AgSbSe₂ were confirmed by XRD and HRTEM analyses. The valence states of Ag⁺, Sb³⁺ and Se²⁻ were confirmed from XPS. The presence of atomic-scale disorder results from Sb–Se bond anharmonicity because of the electrostatic repulsion between the charge of Se and the lone pair of Sb, as well as nanoscale grains coupled with strong Sb–Se bond anharmonicity. This allows for an effective phonon scattering, resulting in reduced thermal conductivity. The AgSbSe₂ system offers promising thermoelectric properties to restore traditional metal tellurides for intermediate power generation. The possible transport mechanism along with lattice anharmonicity created by lone-pair electrons is proposed.