Ultrafast Charge Delocalization Dynamics of Ambient Stable CsPbBr3 Nanocrystals Encapsulated in Polystyrene Fiber.

Abstract

CsPbBr3 nanocrystals (NCs) encapsulated in a transparent polystyrene (PS) fiber matrix (CsPbBr3 @PS) have been synthesized to protect the NCs. The ultrafast charge delocalization dynamics of the embedded NCs have been demonstrated, and the results are compared with the pristine CsPbBr3 in toluene. The electrospinning method was employed for the preparation of CsPbBr3 @PS fibers by using a polystyrene solution doped with pre-synthesized CsPbBr3 and characterized by XRD, HRTEM, and X-ray photoelectron spectroscopy (XPS). Energy level diagrams of CsPbBr3 and PS suggest that CsPbBr3 @PS fibers make a type I core-shell structure. The carrier cooling for CsPbBr3 @PS fibers is found to be much slower than pure CsPbBr3 NCs. This observation suggests that photoexcited electrons from CsPbBr3 NCs get delocalized from the conduction band of the perovskite to lowest unoccupied molecular orbital (LUMO) of the PS fiber matrix. The CsPbBr3 @PS fibers possess remarkable stability under ambient conditions as well as in water over months. The clear understanding of charge carrier relaxation dynamics of CsPbBr3 confined in PS fibers could help to design robust optoelectronic devices.