Boosting Thermoelectric Performance of SnSe via Tailoring Band Structure, Suppressing Bipolar Thermal Conductivity, and Introducing Large Mass Fluctuation.

Here, we report a peak ZT of 1.85 at 873 K for sulfur and Pb codoped polycrystalline SnSe by boosting electrical transport properties while suppressing the lattice thermal conductivity. Compared with single sulfur doped samples, the carrier concentration is improved 1 order of magnitude by Pb incorporation, thereby contributing to improved electrical conductivity and power factor. Moreover, the introduction of sulfur and Pb suppresses the bipolar thermal conductivity by enlarging the band gap. The lattice thermal conductivity significantly decreased as low as 0.13 W m-1 K-1 at 873 K due to the synergic approach involving suppressing bipolar thermal conductivity, large mass fluctuation induced by sulfur incorporation, and nanoprecipitates. We demonstrate that the combination of tailoring band structure, suppressing bipolar thermal conductivity, and introducing large mass fluctuation contributes to the high thermoelectric performance in SnSe. The high performance was achieved through boosting electrical transport properties while maintaining ultralow thermal conductivity. Our findings offer a new strategy for achieving high performance thermoelectric materials.