Chemical Composition Engineering Leading to the Significant Improvement in the Thermoelectric Performance of AgBiSe₂-Based n-Type Solid Solutions

Abstract

In this work, we have improved the thermoelectric performance of n-type AgBiSe 2 by engineering its chemical compositions. This engineering is realized by doping Ag 2 Se at first and then In and S in succession. Finally, the lattice thermal conductivity (κ L ) reduces from 0.39 W K −1 m −1 to 0.15 W K −1 m −1 , and the power factor (PF) enhances from 2.80 μW/(cm K 2 ) to 4.84 μW/(cm K 2 ) at ∼770 K. The reduction in κ L is ascribed to the mass/size mismatch and/or structure anharmonicity, while the enhancement in PF is caused by the improved electrical conductivity via the creation of In and S impurity levels within the gap. As a result, the highest ZT value reaches 0.94 (using measured C p ). This value stands among the highest in the n-type AgBiSe 2 system, which proves that the composition engineering is a practical route to improve the TE performance in this system.