Simultaneous enhanced performance of electrical conductivity and Seebeck coefficient in Bi2−xSnxS3 by solvothermal and microwave sintering

Abstract

The inverse coupled dependence of electrical conductivity and Seebeck coefficient presents a big challenge in achieving a high figure of merit. However, the simultaneous enhancement of electrical conductivity and Seebeck coefficient can be realized in practice by electronic band structure engineering. Resonant level doping shows obvious advantages as one of the most important strategies of band engineering. In this work, single orthorhombic phase Bi2−xSnxS3 (x = 0, 0.005, 0.015, 0.025, 0.05) bulk materials were prepared by combining solvothermal method with microwave sintering. Sn4+ as a dopant increased the electrical conductivity due to tuning carrier concentration (n) and simultaneously “stabilized” the Seebeck coefficient, which is probably ascribed to the effect of resonant level doping. The maximum dimensionless figure of merit (ZT) of Bi2−xSnxS3 (x = 0.015) is 0.67 at 673 K, which was about 8 times higher than that of undoped Bi2S3 samples.