  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.
