Tuning Interlayer Excitons in 2D Semiconducting Heterostructures by Interfacial Charge Transfer

Atomically thin heterostructures from transition metal dichalcogenides (TMDs) show a new class of quasi-particle (i.e., interlayer exciton or IX) with promising optoelectronic properties for next generation excitonic devices and spintronics. To realize the advanced applications, the precise control of the characteristics of IX is necessary. This work introduces a new strategy to control IX selectively by integrating organic layers on top of atomically thin TMD heterostructures. The organic layers form various energy level alignments with monolayer TMDs. Under light illumination, the organic layers regulate the photo-induced charge transfer process at the interfaces. Regardless of irradiation, they may also give rise to dark-state doping on the heterostructure. Depending on the interlayer charge transfer pathways, the emission originating from the radiative recombination of IX can be preserved intact, completely quenched, or moderately modulated. The results also suggest that the IX emission may be predominantly determined by the photoinduced process over dark-state doping. These findings shed critical insights on the nature of IX and advance the realization of IX-based devices.