Deciphering the excited-state dynamics and multicarrier interactions in perovskite core-shell type hetero-nanocrystals.

Deciphering and modulating the carrier dynamics of perovskite nanocrystals (Pe-NCs) is crucial for their optoelectronic applications, which remains elusive to date. Herein, we, for the first time, explore the ultrafast dynamics of perovskite core-shell type NCs using CsPbBr@ZnS as a model system. According to the transient spectroscopic characterization, a physical picture of the ultrafast dynamics in core-shell Pe-NCs is built. Specifically, we directly observed the "hot" hole transfer from CsPbBr to ZnS and confirmed the formation of charge-transfer state in CsPbBr@ZnS NCs. Such ultrafast (<100 fs) hole rearrangement speeds up the carrier cooling and breaks the hot phonon bottleneck effect in Pe-NCs. Moreover, thanks to the charge separation in CsPbBr@ZnS NCs, the Auger recombination is largely suppressed and the Auger lifetime is increased nearly 5-fold compared to that of "pure" CsPbBr NCs, which endows CsPbBr@ZnS NCs with unique optical gain properties. These results are informative for halide perovskite-based applications, such as photocatalysis, hot-carrier photovoltaics and lasers.