Reducing Lattice Thermal Conductivity of the Thermoelectric SnSe Monolayer: Role of Phonon-Electron Coupling

SnSe-based materials possess ultrahigh thermoelectric efficiency and show great potential in next-generation thermoelectric devices. The excellent thermoelectric performance of SnSe has been attributed to its ultralow lattice thermal conductivity. In addition to phonon-phonon interactions, grain boundary, and defect and impurity scatterings, phonon-electron coupling also plays a part in the lattice thermal transport of doped materials, yet it is often overlooked. In this work, we investigated the effect of phonon-electron coupling on the lattice thermal conductivity of the thermoelectric SnSe monolayer. We found that the lattice thermal conductivity decreased by as much as 30% when the carrier density exceeded 10(13) cm(-2) (equivalent to carrier concentration of similar to 10(20) cm(-3)), showing the significant suppression effect. Such level of carrier concentration is often required for thermoelectric conversion, so the contribution of phonon-electron coupling to the reduction for lattice thermal conductivity is as much as other scattering mechanisms and needs to be accounted for engineering phonon transport of thermoelectric materials.