Effects of Dielectric Screening and Charge Transfer Pathways on Interlayer Excitons in Atomically Thin Hybrid Heterostructures

Abstract

Interlayer excitons in 2D heterostructures have been studied extensively as a means to realize the future optoelectronics such as the spin-valleytronics and excitonic devices. Despite significant efforts, the understanding of the parameters that influence interlayer excitons still remain limited. In this work, we have investigated the effects of dielectric screening and charge transfer pathways on interlayer excitons in MoS2/WSe2 heterobilayers. We constructed organic-layer-inserted MoS2/organic/WSe2 hybrid structures using various organic chromophores: 1,3-bis(3,5-dipyrid-3-ylphenyl)benzene (B3PyPB), eosin Y (EY), tetracyanoquinodimethane (TCNQ), and cobalt-centered phthalocyanine (CoPc). We found that the embedded organic layers enhance dielectric screening on interlayer excitons, resulting in a blue-shift of interlayer emission. The interlayer charge transfer between the TMDC layers may also be changed from tunneling to band-assisted transfer with an organic layer that forms the staggered band alignment with TMDC layers. The band-assisted transfer creates a greater population of interlayer excitons, which causes a stronger dipolar interaction and consequently leads to a further PL blue-shift. Lastly, we show that interlayer emission can be quenched by inserting electron or hole trapping organic layers. The results shed critical insights into interlayer excitons and form the basis for next-generation optoelectronic devices.