▎ 摘　　要

Associating atomic vacancies to excited-state transportphenomenain two-dimensional semiconductors demands a detailed understandingof the exciton transitions involved. We study the effect of such defectson the electronic and optical properties of WS2-grapheneand MoS2-graphene van der Waals heterobilayers,employing many-body perturbation theory. We find that chalcogen defectsand the graphene interface radically alter the optical propertiesof the transition-metal dichalcogenide in the heterobilayer, due toa combination of dielectric screening and the many-body nature ofdefect-induced intralayer and interlayer optical transitions. By analyzingthe intrinsic radiative rates of the subgap excitonic features, weshow that while defects introduce low-lying optical transitions, resultingin excitons with non-negligible oscillator strength, they decreasethe optical response of the pristine-like transition-metal dichalcogenideintralayer excitons. Our findings relate excitonic features with interfacedesign for defect engineering in photovoltaic and transport applications.