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

• Published in: Journal of the American Chemical Society Vol. 145; no. 41; pp. 22826 - 22835
• Main Authors: Zhu, Yonghao, Prezhdo, Oleg V., Long, Run, Fang, Wei-Hai
• Format: Journal Article
• Language: English
• Published: American Chemical Society 18.10.2023
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/jacs.3c09170

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 angle-dependent intervalley carrier transfer and recombination in bilayer WS2. 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. B2g breathing, E2g in-plane, and A1g 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.