Filtering the photoluminescence spectra of atomically thin semiconductors with graphene

TL;DR

This paper demonstrates that stacking graphene onto TMD monolayers filters their photoluminescence, producing narrow-line emission from neutral excitons suitable for advanced optoelectronic applications.

Contribution

It introduces a method using graphene to selectively filter TMD photoluminescence, enabling narrow-line emission from neutral excitons in TMD/graphene heterostructures.

Findings

Graphene stacks produce narrow-line photoluminescence from TMDs.

The method applies to multiple tungsten and molybdenum-based TMDs.

TMD/graphene heterostructures are promising for high-rate optoelectronic devices.

Abstract

Atomically thin semiconductors made from transition metal dichalcogenides (TMDs) are model systems for investigations of strong light-matter interactions and applications in nanophotonics, opto-electronics and valley-tronics. However, the photoluminescence spectra of TMD monolayers display a large number of features that are particularly challenging to decipher. On a practical level, monochromatic TMD-based emitters would be beneficial for low-dimensional devices but this challenge is yet to be resolved. Here, we show that graphene, directly stacked onto TMD monolayers enables single and narrow-line photoluminescence arising solely from TMD neutral excitons. This filtering effect stems from complete neutralization of the TMD by graphene combined with selective non-radiative transfer of long-lived excitonic species to graphene. Our approach is applied to four tungsten and molybdenum-based TMDs and establishes TMD/graphene heterostructures as a unique set of opto-electronic building blocks, suitable for electroluminescent systems emitting visible and near-infrared photons at near THz rate with linewidths approaching the lifetime limit.