Quasiparticle level alignment in anthracene-MoS2 heterostructures

Abstract

Heterostructures composed of transition metal dichalcogenides (TMDCs) and organic molecules have been extensively explored for optoelectronic devices. To maximize their application potential, it is essential to investigate the electronic band structures, which govern the charge response of the interfaces to external perturbations. Based on $GW$ calculations, we present a study of organic-inorganic heterostructures with anthracene molecules adsorbed on monolayer MoS2. Building on previous investigations of organic molecule self-assembly at surfaces, we systematically analyze anthracene configurations with various molecular orientations and surface coverages. Partially self-consistent $GW_0$ provides qualitatively different level alignments from those in DFT. Whereas the systems with sparse, horizontally adsorbed anthracenes exhibit type-I alignment, densely packed anthracenes in the head-on position lead to type-II alignment, which indicates the strong dependence of quasiparticle corrections on the interfacial configuration. These findings highlight the importance of level-alignment predictions for both interpreting experiments and guiding the design of organic-inorganic heterostructures.

Figures (7)

• Figure 1: Top views and side views of anthracene/MoS2 heterostructures with F1, H4, F'4.5, and H18 configurations.
• Figure 2: $GW_0$ band structures of anthracene/MoS2 with H4 and F'4.5 configurations. The HOMO and LUMO levels of anthracene are highlighted in red. The Fermi energies are set as 0 eV. The high-symmetry paths $\mathrm{\Gamma-m-k-\Gamma}$ and $\mathrm{\Gamma-X-S-Y-\Gamma}$ are picked from the folded Brillouin zones (Figure \ref{['fig:k-map']} in the Supporting information).
• Figure 3: $GW_0$ band structure calculated along the $\Gamma$-X-S-Y-$\Gamma$ path of the orthorhombic cell in the H18 configuration. The HOMO and LUMO bands of anthracene are highlighted in red. The Fermi energy is set as 0 eV.
• Figure 4: $GW_0$ level alignments between anthracene and MoS2 with different coverage, N anthracenes per 6$\times$6 supercell of MoS2. The VBMs of MoS2 in all cases are aligned at 0 eV. Cases $N=2$ and 3 (F2 and F3) are created with the interlayer distance of the F1 case. The HOMOs (tops of HOMO bands for F'4.5 and H18) of anthracene at $G\textsubscript{0}W\textsubscript{0}$ are marked with black dashed lines.
• Figure S1: K-point mapping in (a) H4, (b) F'4.5, and (c) H18 configurations. The first Brillouin zone of primitive MoS2 is illustrated by dashed lines, and the folded ones are shown by solid lines. The red lines illustrate the high-symmetry paths along which the band structures are plotted.