Electronic Structure, Transport and Phonons of SrAg$Ch$F ($Ch$=S, Se, Te): Bulk Superlattice Thermoelectrics

TL;DR

This study investigates SrAg$Ch$F ($Ch$=S, Se, Te) as promising bulk thermoelectric materials, highlighting their low thermal conductivity, high thermopower, and two-dimensional electronic structures that favor thermoelectric efficiency.

Contribution

The paper provides detailed calculations of electronic, vibrational, and transport properties of SrAg$Ch$F, revealing their potential as bulk superlattice thermoelectrics with favorable thermoelectric characteristics.

Findings

Presence of soft phonons indicating low thermal conductivity

High thermopower at elevated carrier concentrations

Highly two-dimensional electronic bands near valence band maxima

Abstract

We report calculations of the electronic structure, vibrational properties and transport for the p-type semiconductors, SrAg$Ch$F ($Ch$=S, Se and Te). We find soft phonons with low frequency optical branches intersecting the acoustic modes below 50 $cm^{-1}$, indicative of a material with low thermal conductivity. The bands at and near the valence band maxima are highly two dimensional, which leads to high thermopowers even at high carrier concentrations, which is a combination that suggests good thermoelectric performance. These materials may be regarded as bulk realizations of superlattice thermoelectrics.