Enhancing the thermoelectric performance of CexBi2S3 by optimizing the carrier concentration combined with band engineering

Abstract

Bi₂S₃ is a promising low-cost thermoelectric material, but effective chemical modification is needed for its performance enhancement. In this work, we have investigated the effect of Ce on the electronic structure, phase structure, microstructure and TE properties of Ce_xBi₂S₃ (x = 0, 0.01, 0.03, 0.05) fabricated by combining mechanical alloying and spark plasma sintering. The calculated formation energy (ΔE_F) indicates that Ce will enter into interstitial sites of Bi₂S₃ when substitutional sites are saturated. The electronic structure indicates that Ce doping produces a doping band which would reduce E_g and increase m* of pristine Bi₂S₃, and in turn enhancing n_H. When x < 0.03, μ_H and n_H increased simultaneously due to the dominant effect of ionized impurity scattering. Owing to the collaborative optimization of n_H, μ_H, m*, a peak ZT value of 0.33 was obtained at 573 K at x = 0.03, along with a maximum PF value of 298 μW m⁻¹ K⁻², which is about three times higher than that of the pristine Bi₂S₃.