Bottom-up processing of SnTe-AgSbTe2 composites with enhanced thermoelectric performance.

Abstract

SnTe has emerged as a promising lead-free thermoelectric material, yet its practical performance is limited by excessive hole concentration arising from Sn vacancies, low Seebeck coefficient, and excessive thermal conductivity. Herein, we enhance the thermoelectric properties of SnTe by alloying with colloidally synthesized AgSbTe2 nanocrystals containing minor Sb2O3 impurities (denoted as s-AST), synthesized via colloidal nanoparticle assembly and consolidation. The incorporation of s-AST significantly suppresses the lattice thermal conductivity while simultaneously improving the Seebeck coefficient through valence band convergence. Additional phonon scattering from multiscale defects drastically suppresses lattice thermal transport, yielding an ultralow lattice thermal conductivity of 0.45 W m-1 K-1 at 750 K. The synergistic effects of Ag/Sb optimize electronic transport, yielding a remarkable enhancement in power factor of 2.79 mW m-1 K-2. Consequently, the SnTe-8% s-AST composite achieves a peak ZT of 1.28 at 823 K and an average ZT of 0.52 over 400-823 K. This work demonstrates an effective strategy for engineering thermoelectric performance through tailored electronic and phonon engineering in solution-processed SnTe-based thermoelectric materials.