Ultrafast charge transfer in lead sulfide/cadmium sulfide quantum dot-monolayer molybdenum disulfide heterostructures

A hybrid nanostructure formed from colloidal semiconductor quantum dots (QDs) and a monolayer of a transition metal dichalcogenide (TMD) has superior performance over the pristine monolayer TMD in solar harvesting and photodetector applications. This is because the QD component provides most of the light harvesting through its large absorption cross section which sometimes spans a spectral range from ultraviolet to visible and up to near infrared, depending on the QD’s material composition and size. In this presentation we discuss results of time resolved photoluminescence and pump-probe spectroscopic measurements addressing the charge carrier dynamics at the interface of a hybrid nanostructures composed of core/shell PbS/CdS QDs and a monolayer MoS2 where the size of the core QD is varied. We observe long exciton diffusion in photoexcited QDs followed by electron transfer with a core size dependent rate which is maximal for QDs of smallest core size. And a core-size dependent hole transfer from photoexcited MoS2 onto QD with a rate also dependent of the size of the QD.