Hybrid excitations at the interface between a MoS${}_2$ 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 MoS${}_2$ monolayer and the $\pi$-conjugate molecules pyrene and pyridine. For both hybrid systems, the quasi-particle band structure obtained from the $G_0{W}_0$ approximation shows – in contrast to density-functional theory – level alignment of type II, owing to the mutual dynamical screening of the interface constituents. $\mathit{\text{Ab}}\mathit{\text{initio}}$ calculations of the absorption spectrum based on the Bethe-Salpeter equation reveal besides intra-layer excitons on the 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 $\pi$-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.