Unveiling Anomalous Ultrafast Carrier Dynamics of Strong Spectral Overlapping in Few-Layer MoS2

Molybdenum disulfide (MoS₂) nanosheets exhibit significant applications in photoelectric devices, and correctly revealing the photogenerated carrier dynamics in the material is crucial for understanding its photophysical response mechanism and optimizing the photoelectric response efficiency of the devices. Herein, we study the ultrafast photogenerated carrier dynamics in MoS₂ nanosheets using femtosecond time-resolved transient absorption (TA) microscopy and find that the anomalous rebleaching phenomenon of the TA signals for A- and B-excitons takes place at high pump fluences. By performing a careful quantitative fitting of the time-resolved TA signals, we ascribe the anomalous rebleaching to a result of the superposition of photobleaching and photoinduced absorption induced by the bandgap renormalization effect. This work provides new perspectives for elucidating and comprehending the ultrafast carrier dynamics from the complex TA signals, especially when there is an overlap between positive and negative signals.