Hybrid excitations at the interface between a MoS$_2$ monolayer and organic molecules: a first-principles study

TL;DR

This study uses first-principles calculations to explore the electronic and optical properties of MoS$_2$ monolayer hybridized with organic molecules, revealing complex excitonic behaviors and level alignments crucial for optoelectronic applications.

Contribution

It provides the first detailed theoretical analysis of hybrid MoS$_2$-organic interfaces, highlighting the presence of hybrid and charge-transfer excitons and their implications.

Findings

Type II level alignment due to dynamical screening

Presence of intra-layer, hybrid, and charge-transfer excitons

Rich variety of optical excitations in hybrid systems

Abstract

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 $G_0W_0$ approximation shows -- in contrast to density-functional theory -- level alignment of type II, owing to the mutual dynamical screening of the interface constituents. $\textit{Ab initio}$ 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.