Selective Chemical Modulation of Interlayer Excitons in Atomically Thin Heterostructures.

Strongly bound interlayer excitons (XIs) 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 XIs 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 XI 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.