Discovery of the high thermoelectric performance in low-cost Cu8SiSxSe6-x argyrodites

TL;DR

This study reports a newly discovered Cu8SiSxSe6-x argyrodite with high thermoelectric efficiency, stabilized high-symmetry phase, and low cost, making it promising for mid-temperature energy harvesting applications.

Contribution

The paper introduces a novel Cu8SiSxSe6-x argyrodite with stabilized high-symmetry phase and enhanced thermoelectric performance due to Se/S substitution and carrier tuning.

Findings

Achieved ZT of 1.45 in Cu7.95SiS3Se3

Demonstrated ultralow lattice thermal conductivity

Estimated energy conversion efficiency of 13%

Abstract

Cu-based argyrodites have gained much attention as a new class of thermoelectric materials for energy harvesting. However, the phase transition occurring in these materials and low energy conversion performance limited their broad application in thermoelectric converters. In this work, we disclose a newly discovered highly efficient Cu8SiSxSe6-x argyrodite with stabilized high-symmetry cubic phase at above 282 K opening the practical potential of this material for the mid-temperature region applications. The temperature range broadening of the high-symmetry phase existence was possible due to the successful substitution of Se with S in Cu8SiSxSe6-x, which enhances the configurational entropy. The developed argyrodites show excellent thermoelectric performance thanks to the increased density of states effective mass and ultralow lattice thermal conductivity. Further tuning of the carrier concentration through the Cu-deviation improves the thermoelectric performance significantly. The dimensionless thermoelectric figure of merit ZT and estimated energy conversion efficiency {\eta} for Cu7.95SiS3Se3 achieve outstanding values of the 1.45 and 13 %, respectively, offering this argyrodite as a low-cost and Te-free alternative for the thermoelectric energy conversion applications.