Realizing record high performance in n-type Bi2Te3-based thermoelectric materials

Abstract

The application of Bi₂Te₃-based power generation is seriously hindered by the poor n-type samples, demonstrating a strong demand for high-performance n-type Bi₂Te₃-based thermoelectric (TE) materials. However, the strong relationship between thermal and electrical transport limits the improvement of the TE properties. Here, we propose a strategy to enhance the Seebeck coefficient while retaining a large electrical conductivity in n-type (Bi,Sb)₂(Te,Se)₃ materials through introducing electron transport potential wells and texturing. The thermal conductivity was also successfully decreased by constructing multi-scale phonon scattering structures. Consequently, a record maximum and average thermoelectric figure of merit (ZT) of ∼1.4 and ∼1.3 were achieved in the Bi_1.8Sb_0.2Te_2.7Se_0.3 + 15 wt% Te sample at a temperature of 300–575 K. A TE power generation module was fabricated with this n-type material and a home-made p-type Bi₂Te₃ sample. It demonstrated a record conversion efficiency of 6.6% at a temperature gradient of 235 K, representing about an 88% improvement compared with a commercial zone-melt Bi₂Te₃-based module.