Ultrafast Charge Transfer in Van der Waals Heterostructures

Van der Waals heterostructures are assemblies of atomically thin two-dimensional layers held together by weak interlayer forces. When light excites these stacks, electrons and holes can redistribute across the interface on femtosecond to picosecond timescales, a phenomenon known as ultrafast charge transfer. This rapid interfacial dynamics underpins the exceptional performance of next-generation optoelectronic devices, from photodetectors and solar cells to quantum light sources. Key mechanisms include direct electronic injection, exciton dissociation into free carriers, and energy transfer processes that bypass conventional dipole coupling. Control of layer composition, stacking orientation and interlayer spacing allows tuning of transfer rates and pathways. Practical applications range from sub-bandgap photodetection via hot-carrier extraction to dynamic modulation of nonlinear optical responses. A microscopic understanding of the factors governing transfer efficiency—such as electronic coupling, dielectric environment and collective excitations—has grown rapidly, enabling design rules for bespoke heterostructures. The global significance of this field lies in its potential to marry ultrafast physics with scalable device architectures, offering routes to sustainable energy harvesting and ultrahigh-speed information technologies.

Research from Nature Portfolio

Recent studies have revealed multiple interfacial pathways for ultrafast transfer. In a monolayer-WSe₂/graphene heterostructure, layer- and momentum-resolved spectroscopy distinguished direct electron injection from graphene to WSe₂ and a novel Meitner–Auger energy transfer channel that converts excitonic energy in WSe₂ into valence-band transitions in graphene within tens of femtoseconds. This discovery highlighted the dominance of dipole-monopole coupling over Förster- and Dexter-type interactions in certain stacks. Foundational work on MoS₂/WS₂ bilayers demonstrated the formation of interlayer hot excitons on sub-picosecond timescales, explaining how momentum-mismatched excitons nonetheless drive efficient photocurrent generation. Complementary ultrafast mid-infrared probes have captured the emergence of tightly bound interlayer excitons between graphene and MoSe₂ within one picosecond, revealing mass renormalisation of carriers and enhanced charge separation efficiency. Together, these insights establish the interplay of energy and charge channels as central to heterostructure functionality and guide the rational engineering of interfacial coupling.

Ultrafast Charge Transfer in Van der Waals Heterostructures publication trend

The graph below shows the total number of articles in ultrafast charge transfer in van der waals heterostructures across all publications each year (not limited to Nature Index journals).

Technical terms

Van der Waals heterostructure: A stack of two-dimensional materials bound by weak interlayer forces, enabling tunable electronic and optical properties.

Ultrafast charge transfer: Redistribution of photoexcited electrons and holes across an interface on femtosecond to picosecond timescales.

Exciton: A bound state of an electron and a hole held together by Coulomb attraction in a semiconductor.

Hot carrier: A charge carrier possessing excess kinetic energy above the band-edge before thermalisation.

Meitner–Auger energy transfer: A non-radiative interfacial mechanism in which excitonic energy in one layer induces electronic transitions in an adjacent layer via near-field coupling.

References

1. Observation of ultrafast interfacial Meitner-Auger energy transfer in a Van der Waals heterostructure. Nature Communications (2023).
2. Ultrafast formation of interlayer hot excitons in atomically thin MoS2/WS2 heterostructures. Nature Communications (2016).
3. Ultrafast probes of electron–hole transitions between two atomic layers. Nature Communications (2018).
4. Auger‐Assisted Secondary Hot Carrier Transfer in a Type I MoS2/PtSe2 Heterostructure. Advanced Functional Materials (2024).
5. Interfacial Charge Transfer for Enhancing Nonlinear Saturable Absorption in WS2/graphene Heterostructure. Advanced Science (2024).
6. Interfacial charge and energy transfer in van der Waals heterojunctions. InfoMat (2022).