High Thermoelectric Performance of Janus Monolayer and Bilayer HfSSe

For 2D transition metal dichalcogenides (TMDs), the layer thickness has a greater impact on its thermoelectric properties. Herein, the thermoelectric properties of Janus monolayer and bilayer HfSSe are studied based on first‐principles calculations combined with Boltzmann equations, and the thermoelectric properties of bilayer HfSSe are also investigated with different stacking types. Owing to the influence of the interlayer coupling, the degradation of the phonon dispersion curve and the change of the phonon scattering intensity of the bilayer HfSSe lead to the decrease of its lattice thermal conductivity. In addition, the increase in the degeneracy of the electronic band structure of the bilayer HfSSe and the change in the density of states also change the thermoelectric transport properties of electrons. Integrating the coupling of high power factor and low thermal conductivity, the maximum ZT values at room temperature for n‐type doping are predicted as 3.24 and 5.54 for monolayer and SeHfS/SHfSe, respectively. And the ZT values increase to 3.24 and 5.54 as the temperature increases to 600 K. The result manifests that both monolayer and bilayer HfSSe are promising thermoelectric materials, and the layer thickness and stacking types also significantly affect the thermoelectric properties of the 2D TMDs materials.