Donors, Acceptors and a Bit of Aromatics: Electronic Interactions of Molecular Adsorbates on hBN and MoS2 Monolayers

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