Understanding the Effects of Dielectric Property, Separation Distance, and Band Alignment on Interlayer Excitons in 2D Hybrid MoS2/WSe2 Heterostructures

Abstract: Two dimensional (2D) van der Waals heterostructures from transition metal dichalcogenide (TMDC) semiconductors show a new class of spatially separate excitons with extraordinary properties. The interlayer excitons (XI) have been studied extensively, yet the mechanisms that modulate XI are still not well understood. Here, we introduce several organic-layer-embedded hybrid heterostructures, MoS2/organic/WSe2, to study the binding energy of XI. We discover that the dielectric screening of the quasi-particle is reduced with organic molecules due to decreased dielectric constant and greater separation distance between the TMDC layers. As a result, a distinct blueshift is observed in interlayer emission. We also find that the band alignment at the heterointerface is critical. When the organic layer provides a staggered energy state, interlayer charge transfer can transition from tunneling to band-assisted transfer, further increasing XI emission energies due to a stronger dipolar interaction. The formation of XI may also be significantly suppressed with electron or hole trapping molecules. These findings should be useful in realizing XI-based optoelectronics.