Time-domain observation of interlayer exciton formation and thermalization in a MoSe/WSe heterostructure
arXiv:2304.03707 · doi:10.1038/s41467-023-42915-x
Abstract
Vertical heterostructures (HS) of transition metal dichalcogenides (TMDs) host interlayer excitons (ILX), with electrons and holes residing in different layers. With respect to their intralayer counterparts, ILX feature much longer lifetimes and diffusion lengths, paving the way to excitonic optoelectronic devices operating at room temperature. While the recombination dynamics of ILX has been intensively studied, the formation process and its underlying physical mechanisms are still largely unexplored. Here we use ultrafast transient absorption spectroscopy with a white-light probe, spanning both intralayer and interlayer exciton resonances, to simultaneously capture and time-resolve interlayer charge transfer and ILX formation dynamics in a MoSe/WSe HS. We find that the ILX formation timescale is nearly an order of magnitude (~1 ps) longer than the interlayer charge transfer time (~100 fs). Microscopic calculations attribute the relative delay to an interplay between a phonon-assisted interlayer exciton cascade and subsequent cooling processes, and excitonic wave-function overlap. Our results provide an explanation to the efficient photocurrent generation observed in optoelectronic devices based on TMD HS, as the ILX have an opportunity to dissociate during their thermalization process.
18 pages, 4 figures
References in corpus (14)
- Atomically thin p-n junctions with van der Waals heterointerfaces
- Ultrafast Charge Transfer in Atomically Thin MoS2/WS2 Heterostructures
- Observation of Long-Lived Interlayer Excitons in Monolayer MoSe2-WSe2 Heterostructures
- Observation of Moiré Excitons in WSe2/WS2 Heterostructure Superlattices
- k.p theory for two-dimensional transition metal dichalcogenide semiconductors
- Resonantly hybridised excitons in moiré superlattices in van der Waals heterostructures
- Interlayer Exciton Optoelectronics in a 2D Heterostructure p-n Junction
- Ultrafast transition between exciton phases in van der Waals heterostructures
- Direct measurement of key exciton properties: energy, dynamics and spatial distribution of the wave function
- Exciton-Scattering-Induced Dephasing in Two-Dimensional Semiconductors
- First-principles approach to excitons in time-resolved and angle-resolved photoemission spectra
- Ultrafast charge-transfer dynamics in twisted MoS/WSe heterostructures
- Coherent exciton-exciton interactions and exciton dynamics in a MoSe\textsubscript{2}/WSe\textsubscript{2} heterostructure
- Interlayer exciton valley polarization dynamics in large magnetic fields