Improvement in the thermoelectric performance of highly reproducible n-type (Bi,Sb)(2)Se(3)alloys by Cl-doping

Abstract

(Bi,Sb)(2)Se(3)alloys are promising alternatives to commercial n-type Bi-2(Te,Se)(3)ingots for low-mid temperature thermoelectric power generation due to their high thermoelectric conversion efficiency at elevated temperatures. Herein, we report the enhanced high-temperature thermoelectric performance of the polycrystalline Cl-doped Bi2-xSbxSe3(x= 0.8, 1.0) bulks and their sustainable thermal stability. Significant role of Cl substitution, characterized to enhance the power factor and reduce the thermal conductivity synergetically, is clearly elucidated. Cl-doping at Se-site of both Bi(1.2)Sb(0.8)Se(3)and BiSbSe(3)results in a high power factor by carrier generation and Hall mobility improvement while maintaining converged electronic band valleys. Furthermore, point defect phonon scattering originated from mass fluctuations formed at Cl-substituted Se-sites reduces the lattice thermal conductivity. Most importantly, spark plasma sintered Cl-doped Bi(2-x)Sb(x)Se(3)bulks are thermally stable up to 700 K, and show a reproducible maximum thermoelectric figure of merit,zT, of 0.68 at 700 K.