Interlayer excitons and Band Alignment in MoS$_2$/hBN/WSe$_2$ van der Waals Heterostructures

TL;DR

This paper introduces a first-principles computational method combining GW and exciton models to accurately predict band alignment and excitonic properties in MoS2/WSe2 heterostructures, matching experimental results.

Contribution

It develops a general approach to calculate electronic and excitonic properties of incommensurate van der Waals heterostructures using a combination of the QEH model, GW approximation, and 2D Mott-Wannier exciton model.

Findings

Accurately predicts interlayer exciton energies and band alignment.

Shows the importance of self-energy and electron-hole interactions.

Achieves excellent agreement with experimental photoluminescence spectra.

Abstract

Van der Waals heterostructures (vdWH) provide an ideal playground for exploring light-matter interactions at the atomic scale. In particular, structures with a type-II band alignment can yield detailed insight into free carrier-to-photon conversion processes, which are central to e.g. solar cells and light emitting diodes. An important first step in describing such processes is to obtain the energies of the interlayer exciton states existing at the interface. Here we present a general first-principles method to compute the electronic quasi-particle (QP) band structure and excitonic binding energies of incommensurate vdWHs. The method combines our quantum electrostatic heterostructure (QEH) model for obtaining the dielectric function with the many-body GW approximation and a generalized 2D Mott-Wannier exciton model. We calculate the level alignment together with intra and interlayer exciton binding energies of bilayer MoS$_2$/WSe$_2$ with and without intercalated hBN layers, finding excellent agreement with experimental photoluminescence spectra. Comparison to density functional theory calculations demonstrate the crucial role of self-energy and electron-hole interaction effects.