Electronic properties of the MoS2-WS2 heterojunction

TL;DR

This study investigates the electronic structure of MoS2-WS2 heterojunctions, revealing an optically active, spatially separated electron-hole pair system that enables band-gap engineering in 2D semiconductors.

Contribution

First-principles calculations demonstrate that MoS2-WS2 heterojunctions have unique optically active band gaps with spatially separated charge carriers, advancing 2D heterostructure design.

Findings

Heterojunction has an optically active, smaller band gap than individual layers.

Electron-hole pairs are spatially separated across layers.

Heterojunction serves as a model for band-gap engineering in 2D materials.

Abstract

We study the electronic structure of a heterojunction made of two monolayers of MoS2 and WS2. Our first-principles density functional calculations show that, unlike in the homogeneous bilayers, the heterojunction has an optically active band-gap, smaller than the ones of MoS2 and WS2 single layers. We find that that the optically active states of the maximum valence and minimum conduction bands are localized on opposite monolayers, and thus the lowest energy electron-holes pairs are spatially separated. Our findings portrait the MoS2-WS2 bilayer as a prototypical example for band-gap engineering of atomically thin two-dimensional semiconducting heterostructures.