Photocarrier dynamics in heterostructures formed by RuCl₃ and transition metal dichalcogenide monolayers

We report an experimental study on the photocarrier dynamics in van der Waals heterostructures formed by RuCl₃ flakes and transition metal dichalcogenide monolayers, such as MoS₂ and WSe₂. The samples were fabricated using mechanical exfoliation and dry transfer techniques, and characterized by photoluminescence spectroscopy. Transient absorption spectroscopy and microscopy were employed to study the photocarrier dynamics. It has been shown that RuCl₃ can p-dope WSe₂ due to ground-state hole transfer. Our transient absorption measurements indicate that the lifetime of photocarriers injected into highly doped WSe₂ is much shorter than in undoped WSe₂ monolayers. Furthermore, we observed ultrahigh mobility of photocarriers in doped WSe₂ at room temperature. In contrast, photocarriers in RuCl₃/MoS₂ heterostructures exhibit different characteristics. We found no clear evidence of ground-state charge transfer. However, we observed photoinduced interlayer charge transfer between RuCl₃ and monolayer MoS₂, followed by the formation of long-lived interlayer excitons across the van der Waals interface. These results suggest that Mott insulators, such as RuCl₃, could be integrated into van der Waals heterostructures to tune the semiconducting properties of these materials.