Charge transfer mediated anomalous photoluminescence enhancement in monolayer MoS2 graphene heterostructure via polystyrene assisted wet transfer
Van der Waals MoS2 graphene heterostructures are compelling candidates for high performance electronic and optoelectronic device applications. However, the interlayer charge transfer typically quenches the photoluminescence of monolayer MoS2, limiting the use of these heterostructures in light emitting applications. In this work, we report an anomalous photoluminescence enhancement in n-type monolayer MoS2 by integrating it with monolayer graphene via polystyrene assisted wet transfer process. Photoluminescence spectroscopy reveals a dominant trion to exciton conversion in the heterostructure. Kelvin probe force microscopy shows a 600 meV increase in the work function of MoS2 upon heterostructure formation. This work function shift, together with the higher work function of graphene, signifies electron transfer from MoS2 to graphene. Shifts in the graphene G and 2D Raman modes further corroborate the interlayer charge transfer. Hydroxyl and epoxy functionalization of graphene following heterostructure formation is evidenced by X ray photoelectron spectroscopy. DFT based Bader charge analysis quantifies the role of these functional groups in facilitating interlayer charge transfer. Collectively, our findings establish polystyrene assisted wet transfer as a practical interface engineering strategy for enhancing excitonic emission in MoS2 graphene heterostructures, thereby advancing their potential for scalable optoelectronic devices.