Enhanced thermoelectric properties of n-type Cl doped PbS-based materials via Bi alloying

Abstract

PbS-based thermoelectric (TE) materials in the intermediate temperature range have attracted extensive attentions for energy-conversion applications owing to their cost-effectiveness and earth-abundant constituent elements. However, the high TE properties are quite difficult to obtain due to the low carrier concentration and high lattice thermal conductivity (κlat). In this paper, the TE properties of n-type PbS-based materials are enhanced through synergistically optimizing the electrical conductivity (σ) and κlat by Cl doping and Bi alloying. It is found that the substitutions of Cl for S (ClS) and Bi for Pb (BiPb) in lattice remarkably increase the Hall carrier concentration and thus enhance σ, which brings about large power factors (S2σ) of ∼15 μWcm−1K−2 at 573 K and ∼12 μWcm−1K−2 at 823 K. Meanwhile, the introduced ClS and BiPb point defects and micro- or nano-scale precipitates (Bi and Pb) can effectively scatter heat-carrying phonons, resulting in a low κlat. As a consequence, a maxmium ZT value of ∼0.8 at 823 K is acquired for Pb0.99Bi0.01S-0.067%PbCl2, which is ∼1.78 times as high as that of undoped PbS.