Hybrid excitations at the interface between a MoS2 monolayer and organic molecules: A first-principles study

We present a first-principles investigation of the electronic and optical properties of hybrid organic-inorganic interfaces consisting of ${\mathrm{MoS}}_{2}$ monolayer and the $\ensuremath{\pi}$-conjugate molecules pyrene and pyridine. For both hybrid systems, the quasiparticle band structure obtained from the ${G}_{0}{W}_{0}$ approximation shows---in contrast to density-functional theory---level alignment of type I, owing to the mutual dynamical screening of the interface constituents. Ab initio calculations of the absorption spectrum based on the Bethe-Salpeter equation reveal besides intralayer excitons on the ${\mathrm{MoS}}_{2}$ side, hybrid as well as charge-transfer excitons at the interface. These findings indicate that hybrid systems consisting of semiconducting transition-metal dichalcogenides and organic $\ensuremath{\pi}$-conjugate molecules can host a rich variety of optical excitations and thus provide a promising venue to explore many-body interactions and exciton physics in low dimensionality.