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

Abstract

Transition-metal dichalcogenide MoSe2, two-dimensional (2D) materials with a hexagonal lattice, are promising candidates for direct energy conversion due to their excellent thermoelectric properties. Twist and interlayer van der Waals (vdW) force modulation have attracted considerable attention as effective approaches to reduce thermal conductivity and hence improve thermoelectric performance. However, the underlying mechanism analysis of the twist-angle-dependent thermal conductivity remains incomprehensive, and there has been few research 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 molecular dynamics and density functional theory. The results indicated that in the presence of twist angles, the calculated thermal conductivities of 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 angles all decrease monotonically with increasing vdW interaction strength, and structures with twist angles larger than 5° show greater sensitivity to the variation of vdW forces. Twist induces the increase of the lattice constant of bilayer MoSe2, leading to the reduction of the Brillouin zone and the emergence of folded phonon modes. 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 group velocity and phonon lifetime do the reverse. This would provide an effective guide to further elucidate the thermal characteristics and to enhance the efficiency in thermoelectric energy conversion applications of 2D nanothermoelectric materials.

Engineering Symmetry Breaking in Twisted MoS2–MoSe2 Heterostructures for Optimal Thermoelectric Performance

“…The markedly depressed κ can be ascribed to enhanced anharmonic phonon scattering, a direct consequence of in-plane symmetry breaking through an interlayer twist. This twist mechanism contracts the Brillouin zone through an enlargement of the unit cell, thereby introducing additional phonon vibration modes to scatter within the twisted structure. , Such interactions lead to a decrease in the phonon lifetime and a consequent reduction in the phonon mean free path, culminating in the observed thermal transport suppression.…”

Tuning the Thermal Conductivity of Silicon Phononic Crystals via Defect Motifs: Implications for Thermoelectric Devices and Photovoltaics

“…Its dominance in electronic devices not only is due to its electronic properties but also can be partially explained by its low thermal expansion coefficient and relatively high thermal conductivity, which intrinsically promotes efficient heat dissipation . Nonetheless, specific applications require materials with low thermal conductivity, such as thermoelectric devices , and photovoltaics. In the former case, it has been shown that it is possible to increase the thermoelectric efficiency of Si-based structures by phonon engineering. , In the latter case, a Si-based layer can be placed between the conductive layers inside the photovoltaic cell, serving both as electrical and heat insulator. − As a heat insulator, it hinders heat flow and prevents overheating and damage to the device.…”

Twist Proximity-Endowed Large Figure of Merit in a Band-Modulated CrI3/1T-MoS2 Moiré Superlattice

“…Currently, van der Waals (vdW) materials with remarkable physical properties facilitate great interest for cutting-edge technologies. The manifestation of twist degree of freedom in two-dimensional (2D) vdW materials provides outstanding flexibility to tailor their electronic, optical, magnetic properties, etc. − The engineering of the electronic structure by means of twisting may provide excellent control to tune emerging TE transport and various emerging quantum phenomena. The twisting of one layer with respect to the adjacent layer in vdW heterostructures lay down the foundation of moiré superlattices, which can amend the energy band spectrum.…”