Elucidating the Unique Hot Carrier Cooling in Two-Dimensional Inorganic Halide Perovskites: The Role of Out-of-Plane Carrier- Phonon Coupling

the natural semiconductor quantum wells (QWs), which hold great promise for optoelectronics. However, due to the hybrid structure of Ruddlesden???Popper 2D perovskites, the intrinsic nature of hotcarrier kinetics remains shielded within. Herein, we adopt CsPbBr3 nanoplates as a model system to reveal the intrinsic carrier dynamics in inorganic perovskite QWs. Interestingly, we revealed an ultrafast and hot-phonon-bottleneck (HPB)-free carrier cooling in monodisperse CsPbBr3 QWs, which is in sharp contrast to the bulk and nanocrystalline perovskites. The absence of HPB was attributed to the efficient out-of-plane triplet-exciton???LO-phonon coupling in 2D perovskites because of the structural anisotropy. Accordingly, the HPB can be activated by shutting down the outof-plane energy loss route through forming the layer-stacked perovskite superlattice. The controllable on and off of HPB may provide new possibilities in optoelectronic devices and these findings deepen the understanding of a hot-carrier cooling mechanism in 2D perovskites.

Automated summary

This study reveals the intrinsic carrier dynamics in 2D perovskite quantum wells using CsPbBr3 nanoplates as a model system. A ultrafast and hot-phonon-bottleneck-free carrier cooling is observed in monodisperse CsPbBr3 quantum wells, in contrast to bulk and nanocrystalline perovskites. The absence of hot-phonon-bottleneck is attributed to the efficient out-of-plane triplet-exciton-LO-phonon coupling in 2D perovskites.