Realizing High Thermoelectric Performance in Earth-abundant Bi2S3 Compounds by Br Segregation and Dislocation Engineering

Abstract

The primary purpose of this work is to optimize the electrical transport properties of bismuth sulfide (Bi2S3) for thermoelectric application. Herein, the BiBr3 doped Bi2S3 bulk samples are fabricated by solid states reaction combined with spark plasma sintering technology. The electrical transport properties are significantly increased due to the released electron carrier caused by effective Br doping and the slightly scattered electrons in coherent boundary caused by the segregation of extra Br elements. The DFT calculation and SPB model results demonstrate that the Br-doped Bi2S3 samples have superior electrical transport properties benefiting from narrowed bandgap and increased electron localization. The Bi2S2.955Br0.045 sample has a maximum electrical conductivity of 337 S·cm−1 at 323 K, which is two orders of magnitude greater than that of undoped sample. Furthermore, according to the SPB model, a higher carrier concentration boosts the power factor; resulting in a power factor value of 578 μW·m−1·K−1 at 323 K for the Bi2S2.985Br0.015 sample. Simultaneously, the reduced lattice thermal conductivity is due to the enhanced phonon scattering from coherent boundaries and high-density dislocations resulting from lattice deformation and mass fluctuation between Br and S. The Bi2S2.955Br0.045 sample exhibits a low lattice thermal conductivity value of 0.45 W·m−1·K−1 i at 673 K. As a result, the Bi2S2.970Br0.030 sample demonstrates a high ZT value of 0.61 at 673 K and ZTave of 0.40 from 323 to 673 K. Additionally, the theoretical conversion efficiency approaches 6.6%. This can be applied in the domain of power generation across a wide variety of temperatures.