The idea of fabricating artificial solids with band structures tailored to particular applications has long fascinated condensed matter physicists. Heterostructure (HS) construction is viewed as an effective and appealing approach to engineer the novel electronic properties of two dimensional (2D) materials. Different from common 2D/2D heterojunctions where energy transfer is rarely observed, CsPbBr3 quantum dots (0D-QDs) interfaced with 2D materials have become attractive HS for exploring the physics of charge transfer and energy transfer, due to their superior optical properties. In this talk, I will present our experimental study of a new 0D/2D HS, which makes it possible to investigate both light utilization and energy transfer. Specifically, this HS is constructed between monolayer WS2 and CsPbBr3 QDs, and exhibits a hybrid band alignment. The dynamics of energy transfer within the investigated 0D/2D HS is characterized by using femtosecond transient absorption spectrum (TAS) measurements. The TAS results reveal that an ultrafast energy transfer induced by optical excitation is observed from CsPbBr3 QDs to the WS2 layer, which can increase exciton fluence within the WS2 layer up to 69% when compared with pristine ML WS2 under same excitation fluence. Moreover, the formation and dynamics of interlayer excitons have also been investigated and confirmed in the HS, with a calculated recombination time of 36.6 ps. Finally, the overall phenomenological dynamical scenario for the 0D/2D HS is established within 100 ps time region after excitation. The techniques introduced in this work can also be applied to versatile optoelectronic devices based on low dimensional materials. I will also introduce our newly established lab and be happy to explore any mutual collaborations.
Oliphant Seminar Room