Superior thermoelectric properties of ternary chalcogenides CsAgQ (Q = Te, Se) predicted using first-principles calculations.

Tailoring novel thermoelectric materials (TEMs) with a high efficiency is challenging due to the difficulty in realizing both low thermal conductivity and high thermopower factor. In this work, we propose ternary chalcogenides CsAgQ (Q = Te, Se) as promising TEMs based on first-principles calculations of their thermoelectric properties. Using lattice dynamics calculations within self-consistent phonon theory, we predict their ultralow lattice thermal conductivities below 0.