Realizing a thermoelectric conversion efficiency of 10% with long-term stability in a kesterite Cu2ZnSn(S1−xSex)4 single-leg device

Abstract

The application of thermoelectric (TE) technology, contributing to carbon neutrality by the recovery of global waste heat, is hindered by low conversion efficiencies and high costs, demonstrating a strong demand for high-performance TE materials with environmentally friendly characteristics. Multinary Cu₂ZnSnS₄ (CZTS)-based materials have attracted considerable attention for TE power generation owing to their cost-effectiveness and earth-abundant features. However, their dimensionless figure of merit (ZT), which is the critical measure of TE performance, is relatively lower than that of other TE-material-based systems. Herein, we report the discovery of p-type Cu₂ZnSn(S_1−xSe_x)₄ (CZTSSe) single crystals with a record-high ZT of 1.9 at 800 K and high TE conversion efficiency of ∼10% at a temperature difference of 473 K with long-term stability over 1000 h. The exceptional performance originates from a high power factor and intrinsically low thermal conductivity owing to the pseudo-cubic structure, alkali element doping, and short-range lattice distortion. This study demonstrates the potential of CZTS-based TE materials for intermediate-temperature TE harvesting.