Enhancing the thermoelectric performance of CexBi2S3 by optimizing the carrier concentration combined with band engineering
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 CexBi2S3 (x = 0, 0.01, 0.03, 0.05) fabricated by combining mechanical alloying and spark plasma sintering. The calculated formation energy (ΔEF) 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 Eg and increase m* of pristine Bi2S3, and in turn enhancing nH. When x < 0.03, μH and nH increased simultaneously due to the dominant effect of ionized impurity scattering. Owing to the collaborative optimization of nH, μH, 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.