Digital.CSIC. Repositorio Institucional del CSIC

oai:digital.csic.es:10261/337453

18 pages. -- I. Methods. -- II. Supplementary sections. -- Section S1 Estimation of initial Fermi energy and carrier density in graphene. -- Section S2 Thermalized hot carrier distribution in graphene. -- Section S3 Pure photo-thermionic emission (PTE) model. -- Section S4 PTE model involving one defect state Section S5 PTE model involving two defect states. -- III. Supplementary figures. -- Figure S1 UV-vis absorption spectra of WS2 monolayer and graphene-WS2 heterostructure. -- Figure S2 Raman spectra of WS2 monolayer and graphene-WS2 heterostructure. -- Figure S3 Majority conducting carrier density change in graphene based on the pure PTE model. -- Figure S4 Majority conducting carrier density change in graphene based on the PTE model involving one defect state with a fixed defect density. -- Figure S5 Majority conducting carrier density change in graphene based on the PTE model involving one defect state with a fixed defect energy. -- Figure S6 An optical image of the as-prepared electrochemically gated graphene-WS2 heterostructure., Bond-free integration of two-dimensional (2D) materials yields van der Waals (vdW) heterostructures with exotic optical and electronic properties. Manipulating the splitting and recombination of photogenerated electron–hole pairs across the vdW interface is essential for optoelectronic applications. Previous studies have unveiled the critical role of defects in trapping photogenerated charge carriers to modulate the photoconductive gain for photodetection. However, the nature and role of defects in tuning interfacial charge carrier dynamics have remained elusive. Here, we investigate the nonequilibrium charge dynamics at the graphene–WS2 vdW interface under electrochemical gating by operando optical-pump terahertz-probe spectroscopy. We report full control over charge separation states and thus photogating field direction by electrically tuning the defect occupancy. Our results show that electron occupancy of the two in-gap states, presumably originating from sulfur vacancies, can account for the observed rich interfacial charge transfer dynamics and electrically tunable photogating fields, providing microscopic insights for optimizing optoelectronic devices., Peer reviewed