Selective Chemical Modulation of Interlayer Excitons in Atomically Thin Heterostructures

Strongly bound interlayer excitons (X_Is) in atomically thin transition metal dichalcogenide (TMDC) heterostructures such as MoS₂/WSe₂ show promising optoelectronic properties for spin-valleytronics and excitonic devices. The ability to probe and control X_Is is critical for the development of such applications. This Letter introduces a versatile chemical method for selectively tailoring interlayer excitons in TMDC heterostructures. We show that two organic layers form uniform layers on a WSe₂/MoS₂ heterostructure and that the X_I photoluminescence may be either preserved or quenched. The interlayer emission can also be modulated differently by the formation of the organic layer on either side of the TMDC/TMDC heterostructure. We find that the resulting interlayer emission is dominated by selective photoinduced charge transfer over dark-state p-doping effects. These results shed critical insights on interlayer excitons at the TMDC/TMDC heterointerfaces and provide a versatile approach for selectively tailoring them for optoelectronic applications.