Ultrafast carrier dynamics in 2D/0D graphene/MoS₂/PbS quantum dots hybrid heterostructures

Taking advantage of the high carrier mobility of two-dimensional (2D) materials and the tunable broadband absorption property of zero-dimensional (0D) materials, 2D/0D hybrid heterostructures have emerged as new research hotspots in recent years. Although extensive research has been conducted on 2D/0D hybrid heterostructures, most of it focused on application aspects. Therefore, the photophysical response mechanism in 2D/0D heterostructure-especially the ultrafast carrier dynamics and interfacial charge transfer-needs further investigation. Here, we studied the carrier dynamics in 2D/0D graphene/molybdenum disulfide (MoS₂)/lead sulfide (PbS) quantum dots (QDs) hybrid heterostructures via femtosecond time-resolved transient absorption (TA) microscopy. When excited below the bandgap of MoS₂, photogenerated carriers in graphene transferred to MoS₂ within graphene/MoS₂ heterostructures, forming interfacial excitons. The incorporation of PbS QDs extended the optical response of the hybrid heterostructures into the near-infrared region. Moreover, carriers photogenerated in PbS can also transfer to MoS₂, providing an additional channel for the formation and relaxation of interfacial exciton. Consequently, excited carriers in the graphene/MoS₂/PbS QDs hybrid heterostructures exhibited a shortened lifetime due to additional relaxation processes.