High Thermoelectric Performance Achieved by Manipulating the Band Structure and Lattice Dislocations in n‐Type Ge/Pb/Br Codoped Polycrystalline SnSe

ABSTRACT Polycrystalline SnSe has attracted significant attention due to its facile processing, machinability, and scale‐up application. However, n‐type polycrystalline SnSe consistently exhibits inferior thermoelectric performance compared to p‐type polycrystalline, because SnSe is an intrinsic p‐type semiconductor. Here, we promoted the thermoelectric performance of n‐type polycrystalline SnSe through manipulating the band structure and dislocations. The band convergence and enhanced density of states in the electronic structure of SnSe promoted by Pb/Ge/Br codoping, lead to significant enhanced Seebeck coefficient. The carrier concentration was simultaneously enhanced through Ge/Pb/Br codoping. The combination of a large Seebeck coefficient and the enhanced electrical conductivity gives rise to a high power factor as high as 7.47 μW cm −1 K −2 at 873 K. Furthermore, we found that dopants induce strong atomic strain disturbance in the SnSe matrix because of large differences in atom radius with host elements, leading to the formation of high‐density dislocations. The presence of dislocations and nanoprecipitates forms strong phonon scattering centers, effectively scattering phonons and suppressing lattice thermal conductivity. As a result, a high peak ZT of 1.6 has been obtained in n‐type Sn 1.04 Ge 0.02 Pb 0.02 Se 0.97 Br 0.03 .