Improved Thermoelectric Performance in Cu-Based Ternary Chalcogenides Using S for Se Substitution

Abstract

Cu-based ternary chalcogenide semiconductors are a promising class of p-type thermoelectric materials. Here we show that S for Se substitution is a promising route for improving the thermoelectric performance of these compounds, in particular for Cu3SbSe4 and Cu2SnSe3. Phonon scattering due to the combined effects of the atomic mass and size difference between S and Se produces a significant reduction in lattice thermal conductivity over a wide temperature range, and limits the phonon mean free path to its minimum possible value at high temperature. The small electronegativity difference between S and Se is ideal for conserving carrier mobility, as demonstrated by the reasonably large hole mobility in the disordered Cu3Sb(Se1−x S x )4 compounds. These effects along with the low-cost, environmentally benign nature of S, make S for Se substitution a simple yet effective method of improving the thermoelectric performance of Cu-based ternary selenides.