Role of Phonon Scattering and Charge Delocalization on the Ultrafast Carrier Dynamics in CsPbBr ₃ /ZnS Heterostructures

Metal halide perovskite (MHP) nanocrystals are found to be promising for next-generation optoelectronics because of their remarkable photophysical properties. Here, we investigated the hot carrier (HC), exciton, and multiexciton dynamics in CsPbBr₃/ZnS heterostructures. Ultrafast spectroscopic study reveals the enhancement of exciton lifetimes (7.8 → 10.5 ns), retarded HC cooling (390 → 715 fs), and extended biexciton lifetimes (50 → 103 ps) in the heterostructures. First-principles-based density functional theory calculations show a lowered phonon density of states, accounting for slower HC relaxation. Atomic-level heterojunction modulation induces type-II band alignment, spatially separating electrons and holes to extend exciton lifetimes. Interfacial charge delocalization reduces wave function overlap, suppressing Auger recombination. These results highlight heterostructure engineering as a practical approach to control ultrafast carrier dynamics, advancing the design of hot-carrier photovoltaics and multiexciton-based optoelectronic devices.