Tailoring Interlayer Excitons in 2D Van Der Waals Heterostructures with Molecular Functionalization

Abstract

Two-dimensional (2D) van der Waals (vdW) heterostructures from transition metal dichalcogenide (TMDC) semiconductors offer a new class of interlayer excitons with promising optoelectronic properties for the next-generation optoelectronics such as excitonic devices and spintronics. To realize such applications, the unique properties of interlayer excitons must be thoroughly understood and precisely controlled. This work introduces a new strategy to selectively modulate interlayer excitons by functionalizing organic chromophore molecules. We explored two dye molecules, tetracyanoquinodimethane (TCNQ) and eosin Y (EY), and deposited their uniform layers on vdW heterostructures from MoS2 and WSe2 monolayers. We demonstrate that photoinduced charge transfer between MoS2 and WSe2 may be promoted or suppressed by the organic layers, thus affecting the photoluminescence (PL) emissions. Kelvin probe force microscopy (KPFM) shows that dark-state doping may also affect the interlayer excitons, yet we find that photoinduced charge transfer plays a dominant role. Our results elucidate interlayer excitons at the heterointerfaces and lay the foundation for diverse optoelectronic applications.