The design of low-dimensional organic-inorganic hybrid interfaces for the next generation of optoelectronic applications requires an in-depth understanding of the microscopic mechanisms ruling the electronic interactions in these systems. In this work, we present a first-principles study based on density-functional theory inspecting the structural, energetic, and electronic properties of five molecular donors and acceptors adsorbed on freestanding hexagonal boron nitride (hBN) and molibdenum disulfide (MoS2) monolayers. All considered heterostructures are stable, due to the crucial contribution of dispersion interactions, which are maximed by the overall flat arrangement of the physisorbed molecules on both substrates. The level alignment of the hybrid systems depends on the characteristics of the constituents. On hBN, both type-I and type-II heterostructures may form, depending on the relative energies of the frontier orbitals with respect to the vacuum level. On the other hand, all MoS2-based hybrid systems exhibit a type-II level alignment, with the molecular frontier orbitals positioned across the energy gap of the semiconductor. The electronic structure of the hybrid materials is further determined by the formation of interfacial dipole moments and by the wave-function hybridization between the organic and inorganic constituents. These results provide important indications for the design of novel low-dimensional hybrid materials with suitable characteristics for optoelectronics.

Grants: Swiss National Supercomputing Centre (CSCS) under project s965 "Molecules at interfaces from density functional theory" University of Zürich Forschungskredit Postdoctoral Fellowship German Research Foundation (DFG), project number 182087777 - CRC 951 Computational resources from the North-German Supercomputing Alliance (HLRN), project bep00104 German Federal Ministry of Education and Research (Professorinnen-programm III) - State of Lower Saxony (Professorinnen für Niedersachsen)