Geometry And Greatly Enhanced Thermoelectric Performance Of Monolayer Mxy Transition-Metal Dichalcogenide: Moste As An Example

2D thermoelectric materials with a high power factor and low lattice thermal conductivity have recently been the focus of cutting-edge research. Herein, combining first-principles calculations and semiclassical Boltzmann transport theory, a structural search on the monolayer transition-metal dichalcogenide MoSTe is conducted and its electronic structure, lattice dynamics, and thermoelectric properties are carefully studied. A new tetragonal blend structure is found that is both energetically and dynamically more stable than the experimentally synthesized hexagonal Janus structure, and this blend structure possesses strong anisotropic in-plane electron and phonon transport properties. Both structures have insulating ground states, which allow a reasonable Seebeck coefficient. Phonon dispersion reveals that several optical phonon-branches downshift and overlap with the acoustic branches, leading to an enhanced scattering rate, greatly reduced lattice thermal conductivity, and eventually excellent thermoelectric performance with ZT = 0.34 at 300 K and 1.0 at 600 K for the blend-MoSTe. The results demonstrate the great potential of the monolayer MXY transition-metal dichalcogenide in thermoelectric applications.