Theoretical study on electronic structure and thermoelectric properties of PbS_xTe_1-x (x=0.25, 0.5, and 0.75) solid solution

The electronic structure and thermoelectric (TE) properties of PbSxTe_1-x (x=0.25, 0.5, and 0.75) solid solution have been studied by combining the first-principles calculations and semi-classical Boltzmann theory. The special quasi-random structure (SQS) method is used to model the solid solutions of PbSxTe_1-x, which can produce reasonable electronic structures with respect to experimental results. The maximum zT value can reach 1.67 for p-type PbS_0.75Te_0.25 and 1.30 for PbS_0.5Te_0.5 at 800 K, respectively. The performance of p-type PbSxTe_1-x is superior to the n-type ones, mainly attributed to the higher effective mass of the carriers. The zT values for PbSxTe_1-x solid solutions are higher than that of pure PbTe and PbS, in which the combination of low thermal conductivity and high power factor play important roles.