Cavity-Reconstructed Exciton Relaxation and Charge Transfer in WS₂/MoS₂ Junctions

Interfacial charge and energy transfer critically control excited-state exciton dynamics in two-dimensional transition metal dichalcogenide (TMD) junctions and offer a promising avenue for external control via strong light-matter interactions in optical microcavities. In this work, we develop an exciton-based nonadiabatic molecular dynamics framework that combines linear-response time-dependent density functional theory with the Pauli-Fierz formulation of cavity quantum electrodynamics, and apply it to systematically investigate cavity-modified energy relaxation and charge transfer processes in H-stacked WS₂/MoS₂ junctions. In the absence of a microcavity, exciton energy relaxation is found to be governed by hole transfer from the K valley to the Γ valley, which constitutes the rate-limiting step due to the combined effects of energy and momentum mismatches. Upon coupling to an optical microcavity, exciton-photon hybridization generates polaritonic intermediate states with pronounced interlayer character, thereby reconstructing the excitonic relaxation pathways and accelerating both energy dissipation and charge transfer. This enhancement is most prominent in dual-mode microcavities that are simultaneously near-resonant with the intralayer bright excitons of both constituent layers, leading to the fastest relaxation dynamics. These results reveal the microscopic mechanism by which optical microcavities regulate nonequilibrium exciton dynamics in TMD junctions and establish cavity-engineered polaritonic states as an effective strategy for controlling exciton relaxation and interfacial charge transfer in low-dimensional materials.