Long-Lived Photogenerated Carriers in 2D MoS₂ Flakes Chemically Exfoliated

MoS₂ is a bidimensional material, belonging to the class of transition metal dichalcogenides (TMDs). Its semiconducting 2H phase has unique optoelectronic properties, due to its strong light-matter interaction and chemical stability in both mono- or few-layer form. As a result, it is an excellent candidate for light harvesting applications, which rely on the photogeneration of sufficiently long-lived charge carriers.<br/>Liquid phase exfoliation (LPE) is a high yield and industrially scalable technique to produce high quality nanosheet colloidal dispersions that can be easily processed and incorporated into device fabrication processes.<br/>In this study, we investigate LPE MoS₂samples using time-resolved optical spectroscopy. The transient response of this material is dictated by the formation and recombination of bound states, e.g. excitons and trions. Using a specially designed pump-probe setup, we measured the lifetime of these photoexcited states from the femtosecond to microsecond range. We observe spectral features related to charge carriers with lifetimes up to ~ 100 ns. A comparison between different exfoliation techniques aims at understanding the role of the different thicknesses and details of the nanosheet morphology on the photo-generated charge carrier dynamics.