Highly enhanced thermoelectric performance in (In, Pb) co-doped Bi-Sb-Te alloys via synergistic modulation of carrier concentration and band structure

Abstract

The extensive utilization of thermoelectric (TE) conversion technology necessitates stricter performance requirements for bismuth telluride (Bi₂Te₃)-based commercial materials. Despite the numerous optimization methods available for Bi₂Te₃-based materials, each optimization method has a certain upper limitation, and combining multiple strategies can achieve the optimal thermoelectric figure of merit (zT). In this study, the thermoelectric properties of (Bi,Sb)₂Te₃ materials are enhanced through the combined use of the heavy element Pb to regulate carrier concentration and the In element to optimize the band structure. Notably, indium (In) can suppress p-type antisite defects, which generate abundant Te vacancies, and help regulate the carrier concentration to its optimal level. This co-doping strategy achieves optimal carrier concentration, thereby enhancing the power factor (PF=4.57×10³ μW⸱m^–1⸱K^–2), and generating abundant dislocations, the presence of the rich nano-second phase Sb₂O₃ contributes to reduced lattice thermal conductivity. Consequently, a peak zT value of 1.41 at 323 K and a high average zT value of 1.23 between 300 K and 500 K are achieved. Additionally, two pairs of thermoelectric modules, composed of p-type (Bi_0.42Sb_1.58)_0.994(In, Pb)_0.006Te₃ and zone-melted n-type Bi₂Te_2.7Se_0.3, demonstrate a conversion efficiency of 7.3% at a temperature difference of 250 K. This underscores the promising potential of these thermoelectric modules in commercialization. Thus, this study demonstrates the feasibility of combining multiple strategies and is expected to provide a potential reference for other thermoelectric systems.