Optimization of the Intrinsic Electrical and Thermal Transport Properties of Sb2Si2Te6 via Tensile Strain: A First-Principles Study

A promising thermoelectric material, Sb2Si2Te6, which has an intrinsically low thermal conductivity and a considerable figure of merit (ZT) of 1.08 at 823 K, was recently reported. In this work, we study the effect of strain on the electronic structure and electrical transport performance of Sb2Si2Te6 via density-functional calculations. When the out-of-plane tensile strain is applied, the Seebeck coefficient of p-type Sb2Si2Te6 increases due to the flattened electronic dispersion near the valence band edge and the larger DOS effective mass. An enhancement of the power factor along the out-of-plane direction of strained p-type Sb2Si2Te6 is observed in a wide range of carrier concentrations. Meanwhile, the change of lattice thermal conductivity of strained Sb2Si2Te6 is estimated by the modified Debye–Callaway model. The lattice thermal conductivity of Sb2Si2Te6 decreases under out-of-plane tensile strain due to the smaller phonon group velocities and larger Grüneisen parameters.