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

Two-dimensional (2D) van der Waals heterostructures from transition metal dichalcogenide (TMDC) semiconductors show spatially separate excitons with extraordinary properties. The interlayer excitons (X-I) have been studied extensively, yet the mechanisms that modulate X-I are still not well understood. Here, we introduce several organic-layer-embedded hybrid heterostructures, MoS2/organic/WSe2, to study the binding energy of X-I. We discover that the dielectric screening of the quasiparticle is reduced with organic molecules due to a 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 X-I emission energies due to a stronger dipolar interaction. The formation of X-I may also be significantly suppressed with electron or hole trapping molecules. These findings should be useful in realizing X-I-based optoelectronics.