Ultrafast Charge Transfer Cascade in a Mixed-Dimensionality Nanoscale Trilayer

Innovation in optoelectronic semiconductor devices is driven by a fundamental understanding of how to move charges and/or excitons (electron-hole pairs) in specified directions for doing useful work, e.g. for making fuels or electricity. The diverse and tunable electronic and optical properties of two-dimensional (2D) transition metal dichalcogenides (TMDCs) and one-dimensional (1D) semiconducting single-walled carbon nanotubes (s-SWCNTs) make them good quantum confined model systems for fundamental studies on charge and exciton transfer across heterointerfaces. Here we demonstrate a mixed-dimensionality 2D/1D/2D MoS2/SWCNT/WSe2 hetero-trilayer that enables ultrafast photoinduced exciton dissociation, followed by charge diffusion and slow recombination. Importantly, the hetero-trilayer serves to double charge carrier yield relative to a MoS2/SWCNT hetero-bilayer, and also demonstrates the ability of the separated charges to overcome inter-layer exciton binding energies to diffuse from one TMDC/SWCNT interface to the other 2D/1D interface, resulting in coulombically unbound charges. Interestingly, the hetero-trilayer also appears to enable ef- ficient hole transfer from SWCNTs to WSe2, which is not observed in the identically prepared WSe2/SWCNT heterobilayer, suggesting that new dynamic pathways may be opened up by increasing the complexity of nanoscale heterostructures. Our work suggests "mixed-dimensionality" TMDC/SWCNT based hetero-trilayers as both inter- esting model systems for mechanistic studies of carrier dynamics at nanoscale heteroin- terfaces, and for potential applications in advanced optoelectronic systems.