Cu Intercalation and Br Doping to Thermoelectric SnSe2 Lead to Ultrahigh Electron Mobility and Temperature‐Independent Power Factor

Abstract Due to its single conduction band nature, it is highly challenging to enhance the power factor of SnSe2 by band convergence. Here, it is reported that simultaneous Cu intercalation and Br doping induce strong Cu–Br interaction to connect SnSe2 layers, otherwise isolated, via “electrical bridges.” Atom probe tomography analysis confirms a strong attraction between Cu intercalants and Br dopants in the SnSe2 lattice. Density functional theory calculations reveal that this interaction delocalizes electrons confined around SnSe covalent bonds and enhances charge transfer across the SnSe2 slabs. These effects dramatically increase electron mobility and concentration. Polycrystalline SnCu0.005Se1.98Br0.02 shows even higher electron mobility than pristine SnSe2 single crystal and the theoretical expectation. This results in significantly improved electrical conductivity without reduci…