Weakening of the Many-Body Interactions Induced by Charge Transfer in Gr/WS₂ Heterostructures

Two-dimensional transition-metal dichalcogenides (TMDCs) offer low-dimensional and strongly confined systems, making them important materials for fabricating novel optoelectronic devices and exploring the interaction between light and matter. However, in practical application processes, there are a series of issues that need to be addressed, including how to separate the electrons and holes generated by strong light–material interactions and how to weaken or avoid the many-body interactions caused by low-dimensional systems. The heterostructures formed by stacking TMDCs and graphene have been extensively studied as a means to separate electron–hole pairs in TMDCs via photoinduced charge transfer. However, due to the complexity of many-body interactions, there is still limited research on the impact of incorporating graphene on the many-body interactions in TMDCs. In this study, we report the slowing down of carrier relaxation in WS2 after forming heterostructures with graphene under excitation conditions above the WS2 band gap. After assigning lifetimes obtained from fitting transient absorption spectra, we show the complete carrier relaxation process in the heterostructure of WS2 and graphene and attribute the slowing of carrier relaxation in WS2 to the reduction in carrier density caused by direct hole transfer from WS2 to graphene, weakening the many-body annihilation processes associated with carrier density. This study shows the impact of WS2 forming heterostructures with graphene on the many-body interactions within WS2, which provides valuable insights for the development of optoelectronic devices involving TMDCs.