In a study just published in ACS Nano, the team investigated what happens when monolayer MoS₂ — a direct-gap semiconductor just three atoms thick — is stacked with graphene. This combination of two-dimensional (2D) materials reveals a subtle but powerful mechanism: electrical control over light emission without relying on high levels of doping.
By carefully tuning the interaction between MoS₂ and graphene, the researchers observed a dramatic suppression of photoluminescence (light emission) from specific exciton species (bound electron-hole pairs), depending on whether the material was isolated or part of a stacked heterostructure. The introduction of graphene changes the game: it enables efficient, voltage-controlled charge transfer, preventing the accumulation of excess carriers in MoS₂ and thus keeping the optical response stable and predictable.
The most striking insight? In pristine MoS₂, high doping leads to a superlinear increase in light emission — a kind of optical “amplification” that stops once the system is saturated. This effect disappears completely in the MoS₂/graphene stack, showing that graphene acts as a natural “exciton regulator,” draining away excess charge and suppressing this nonlinearity.
Even B-type excitons — typically unaffected by doping due to their ultrafast decay — are modulated by this setup, revealing that charge transfer occurs before excitons can recombine internally. This suggests the presence of a hot-electron transfer channel, a new dimension to 2D material photophysics.
Why it matters
This work opens the door to more precise control over how atomically thin materials emit light, essential for developing efficient LEDs, photodetectors, and quantum light sources. The use of layered 2D materials to achieve such control, without chemical treatment or structural modification, marks a significant leap forward in optoelectronics and nanophotonics.
The SUPERVenice perspective
This discovery strengthens Venice’s growing role in frontier materials research. The participation of Ca’ Foscari University through Prof. Domenico De Fazio, member of SUPERVenice, highlights the impact of collaborative, interdisciplinary science rooted in fundamental physics with clear technological implications.
The full paper, “Tunable Exciton Modulation and Efficient Charge Transfer in MoS₂/Graphene van der Waals Heterostructures”, is available open-access in ACS Nano.
🔬 Read the paper: ACS Nano DOI