Origins of promising thermoelectric performance in quaternary selenide BaAg2SnSe4

Abstract

Motivated by the recent discovery of low thermal conductivity in 1-2-1-4 quaternary selenides, we studied the origins of promising thermoeletric performance of BaAg2SnSe4 using ab initio calculations. We have shown that BaAg2SnSe4 is a model material of valley degeneracy, either conduction valleys or valence valleys are highly degenerate, yielding promising electronic transport performance. Meanwhile, the extremely low thermal conductivity arises primarily from lattice contribution. Due to both advantages of electronic and phonon transport properties, the calculated thermoelectric figure of merit ZT exceeds 1 at room temperature. Our results highlight the advantages of quaternary BaAg2SnSe4 as a promising bulk thermoelectric material.