Thickness-Dependent Dark-Bright Exciton Splitting and Phonon Bottleneck in CsPbBr₃-Based Nanoplatelets Revealed via Magneto-Optical Spectroscopy.

ABSTRACT: The optimized exploitation of perovskite nanocrystals and nanoplatelets as highly efficient light sources requires a detailed understanding of the energy spacing within the exciton manifold. Dark exciton states are particularly relevant because they represent a channel that reduces radiative efficiency. Here, we apply large in-plane magnetic fields to brighten optically inactive states of CsPbBr₃-based nanoplatelets for the first time. This approach allows us to access the dark states and directly determine the dark-bright splitting, which reaches 22 meV for the thinnest nanoplatelets. The splitting is significantly less for thicker nanoplatelets due to reduced exciton confinement. Additionally, the form of the magneto-PL spectrum suggests that dark and bright state populations are nonthermalized, which is indicative of a phonon bottleneck in the exciton relaxation process.

SUBMITTER: Wang S 

PROVIDER: S-EPMC9479212 | biostudies-literature | 2022 Sep

REPOSITORIES: biostudies-literature