Engineering phonon transport in MoS 2 lattice by substituting isovalent anion (Se) for low thermal conductivity via all-scale hierarchical phonon scattering

MoS 2 -based transition metal dichalcogenides (TMDCs) have received extensive attention in thermoelectric devices due to its tunable operating temperature from room temperature to mid-temperature applications. Herein, Se-substituted MoS 2 is synthesized by a hydrothermal method, and the thermoelectric properties are systematically investigated to understand the influence of Se substitution. The X-ray diffraction results confirm the phase purity of the Se-substituted MoS 2 . The Se substitution results in creating flake-like morphology as evidenced by the HRSEM images and the XPS confirming the chemical composition of MoS 2- x Se x . The influence of heavier Se substitution on phonon group velocity was inferred from the variation in cell volume and lattice parameter. The hexagonal crystal structure is sustained at all Se concentrations, where the heavier isovalent Se substitution promotes mass-fluctuation, grain boundary, and point defect phonon scattering. Therefore, a notable reduction in thermal conductivity is observed for Se substitution and highly reduced lattice thermal conductivity of 0.44 Wm −1 K −1 at 563 K.