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

Abstract CsPbBr 3 nanocrystals (NCs) encapsulated in a transparent polystyrene (PS) fiber matrix (CsPbBr 3 @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 CsPbBr 3 in toluene. The electrospinning method was employed for the preparation of CsPbBr 3 @PS fibers by using a polystyrene solution doped with pre‐synthesized CsPbBr 3 and characterized by XRD, HRTEM, and X‐ray photoelectron spectroscopy (XPS). Energy level diagrams of CsPbBr 3 and PS suggest that CsPbBr 3 @PS fibers make a type I core–shell structure. The carrier cooling for CsPbBr 3 @PS fibers is found to be much slower than pure CsPbBr 3 NCs. This observation suggests that photoexcited electrons from CsPbBr 3 NCs get delocalized from the conduction band of the perovskite to lowest unoccupied molecular orbital (LUMO) of the PS fiber matrix. The CsPbBr 3 @PS fibers possess remarkable stability under ambient conditions as well as in water over months. The clear understanding of charge carrier relaxation dynamics of CsPbBr 3 confined in PS fibers could help to design robust optoelectronic devices.