Ultrafast Exciton Dynamics in Colloidal CsPbBr3 Perovskite Nanocrystals: Biexciton Effect and Auger Recombination

Exciton many-body interaction is the fundamental light–matter interaction that determines the optical response of the new class of colloidal perovskite nanocrystals of the general formula CsPbX3 [X = Cl, Br, or I]. However, the understanding of exciton many-body interactions manifested through the transient biexcitonic Stark effect at the early time scales and the Auger recombination process in this new class of materials still remains rather incomplete. In this Article, we studied the many-body exciton interactions under controlled conditions through ultrafast transient absorption spectroscopy. A large biexcitonic redshift ∼30 meV to the effect of hot excitations on the excitonic resonance is observed at the early time scales. From the fluence-dependent studies, it is evident that the samples have only single and biexciton lifetimes, suggesting that the band edges are 2-fold degenerate. This explicit experimental evidence for the exciton many-body interactions in CsPbBr3 nanocrystals provides a powerful tool to explore the development of their prospective applications in light-emitting devices, lasers, and solar cells.