Thickness-Dependent Dark-Bright Exciton Splitting and Phonon Bottleneck in CsPbBr<sub>3</sub>-Based Nanoplatelets Revealed via Magneto-Optical Spectroscopy
Shuli Wang, Mateusz Dyksik, Carola Lampe, Moritz Gramlich, D. K. Maude, Michał Baranowski, Alexander S. Urban, Paulina Płochocka, Alessandro Surrente
Abstract
High Resolution Image Download MS PowerPoint Slide 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 CsPbBr 3 -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.