Twist Angle-Dependent Intervalley Charge Carrier Transfer and Recombination in Bilayer WS₂

Abstract

A twist angle at a van der Waals junction provides a handle to tune its optoelectronic properties for a variety of applications, and a comprehensive understanding of how the twist modulates electronic structure, interlayer coupling, and carrier dynamics is needed. We employ time-dependent density functional theory and nonadiabatic molecular dynamics to elucidate angledependent intervalley carrier transfer and recombination in bilayer WS 2 . Repulsion between S atoms in twisted configurations weakens interlayer coupling, increases the interlayer distance, and softens layer breathing modes. Twisting has a minor influence on K valleys while it lowers Γ valleys and raises Q valleys because their wave functions are delocalized between layers. Consequently, the reduced energy gaps between the K and Γ valleys accelerate the hole transfer in the twisted structures. Intervalley electron transfer proceeds nearly an order of magnitude faster than hole transfer. The more localized wave functions at K than Q values and larger bandgaps result in smaller nonadiabatic couplings for intervalley recombination, making it 3−4 times slower in twisted than high-symmetry structures. B 2g breathing, E 2g in-plane, and A 1g out-of-plane modes are most active during intervalley carrier transfer and recombination. The faster intervalley transfer and extended carrier lifetimes in twisted junctions are favorable for optoelectronic device performance.

Theoretical Investigation on Tunable Bipolar Ferromagnetic Half-Metallicity in VI2/V3I8 Two-Dimensional Heterostructures: Applications for Spintronic Devices

“…Furthermore, the effect of interlayer distance ( d ) on the electronic and magnetic properties of the VI 2 /V 3 I 8 HS is investigated. In experiment, many effective methods have been proposed to the modulate the interlay distance of layered structures, such as hydrostatic pressure, external strains, , intercalating hetero sublayers, changing the twist angle of bilayers, , and so on. The energy difference between the FM and AFM states (Δ E = E FM – E AFM ) as a function of interlayer distance is shown in Figure f.…”

Controlling Charge Carrier Dynamics in Porphyrin Nanorings by Optically Active Templates

“…The present systems of interest are stable at room temperature and do not exhibit any structural deformations, such as reorganization, isomerization, or fragmentation, upon photoexcitation. Hence, the CPA can be successfully applied − to treat the heavier nuclear degrees of freedom classically with Newton’s equation of motion. The lighter electrons are described quantum mechanically, and their evolution depends parametrically on the nuclear trajectory.…”

Energy-Conserving and Thermally Corrected Neglect of Back-Reaction Approximation Method for Nonadiabatic Molecular Dynamics

“…Nonadiabatic molecular dynamics (NA-MD) is a widely adopted family of computational methods to model quantum dynamics of excited states in various systems. − The NA-MD simulations have found their use in describing various kinds of processes in many molecular and condensed-matter systems: modeling nonradiative electron–hole recombination and “hot” carrier relaxation in quantum dots and molecular clusters, − nanotubes, , plasmonic systems, or exotic states of matter; modeling photoinduced isomerization and reactive processes in various molecular systems; − and modeling charge transfer and charge carrier trapping processes in 2D materials, − interfaces, ,− ,, organic solids, , and pristine and defect-containing bulk semiconductors. − …”

“…N onadiabatic molecular dynamics (NA-MD) is a widely adopted family of computational methods to model quantum dynamics of excited states in various systems. 1−5 The NA-MD simulations have found their use in describing various kinds of processes in many molecular and condensed-matter systems: modeling nonradiative electron−hole recombination and "hot" carrier relaxation in quantum dots and molecular clusters, 6−13 nanotubes, 14,15 plasmonic systems, 16 or exotic states of matter; 17 modeling photoinduced isomerization and reactive processes in various molecular systems; 18−22 and modeling charge transfer and charge carrier trapping processes in 2D materials, 23−31 interfaces, 25,[32][33][34][35][36]36,37 organic solids, 38,39 and pristine and defect-containing bulk semiconductors. 40−46 Computing the nonadiabatic dynamics in atomistic and solidstate systems has been made possible by adopting quantumclassical trajectory surface hopping (TSH) techniques, 4,47−51 among which Tully's fewest switches surface hopping (FSSH) 52 has been one of the most popular choices due to its simplicity to implement and clear physical picture.…”