Understanding the Effects of Dielectric Property and Band Alignment on Interlayer Excitons in 2D van der Waals Heterostructures

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 greatly enhanced with organic molecules having a large energy gap, resulting in a distinct blue shift in interlayer emission, and that the band alignment is also critical. When the organic layer provides a staggered energy state, interlayer charge transfer can transition from tunneling to band-assisted transport, further increasing XI emission energies due to a stronger dipolar interaction. The formation of XI may also be significantly suppressed using electron or hole trapping molecules. These findings should be useful in realizing XI-based optoelectronics.