Enhancing Thermoelectric Performance of n-Type Hot Deformed Bismuth-Telluride-Based Solid Solutions by Nonstoichiometry-Mediated Intrinsic Point Defects

Abstract

Bismuth-telluride-based solid solutions are the unique thermoelectric (TE) materials near room temperature. Various approaches have been applied to enhance the thermoelectric performance, and much progress has been made in their p-type materials. However, for the n-type counterparts, little breakthrough has been obtained. We herein report on enhancing thermoelectric performance of n-type bismuth-telluride-based alloys by nonstoichiometry to mediate the point defects, combined with one-time hot deformation. The improved power factor of 3.3 × 10^-3 W m^-1 K^-2 and reduced lattice thermal conductivity contribute to a high figure-of-merit, zT, of 1.2 at 450 K for n-type Bi₂Te_2.3Se_0.69 alloys with Se deficiency. The high zT is comparable to that of Bi₂Te_2.3Se_0.7 hot deformed three times, which is a practically complicated process. The results demonstrate that nonstoichiometry can be an effective and simple strategy in mediating intrinsic point defects and enhancing the thermoelectric performance of bismuth-telluride-based alloys.