Twist-Angle-Dependent Phonon Transport of van der Waals MoSe₂ Thermoelectric Materials for the Recycling of Waste Heat

HP Xiong and XH Nie and L Zhao and S Deng and XY Song, ACS APPLIED NANO MATERIALS, 6, 15685-15696 (2023).

DOI: 10.1021/acsanm.3c02512

Transition-metal dichalcogenide MoSe2, two-dimensional(2D) materials with a hexagonal lattice, are promising candidatesfor direct energy conversion due to their excellent thermoelectricproperties. Twist and interlayer van der Waals (vdW) force modulationhave attracted considerable attention as effective approaches to reducethermal conductivity and hence improve thermoelectric performance.However, the underlying mechanism analysis of the twist-angle-dependentthermal conductivity remains incomprehensive, and there has been fewresearch on the joint effects of twist and interlayer coupling strength.In this study, the heat transfer of monolayer and bilayer MoSe2 was systematically investigated by nonequilibrium moleculardynamics and density functional theory. The results indicated thatin the presence of twist angles, the calculated thermal conductivitiesof monolayer and bilayer MoSe2 both exhibit "W-shaped",achieving a maximum decrease of 56.6%. For bilayer MoSe2, the thermal conductivities corresponding to different twist anglesall decrease monotonically with increasing vdW interaction strength,and structures with twist angles larger than 5 & DEG; show greatersensitivity to the variation of vdW forces. Twist induces the increaseof the lattice constant of bilayer MoSe2, leading to thereduction of the Brillouin zone and the emergence of folded phononmodes. The characteristics that dominate heat transfer, heat capacity,phonon group velocity, and phonon lifetime, display divergent tendencies,with heat capacity increasing with lattice constant while phonon groupvelocity and phonon lifetime do the reverse. This would provide aneffective guide to further elucidate the thermal characteristics andto enhance the efficiency in thermoelectric energy conversion applicationsof 2D nanothermoelectric materials.

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