Neutral and Charged Exciton Fine Structure in Single Lead Halide Perovskite Nanocrystals Revealed by Magneto-optical Spectroscopy

Revealing the crystal structure of lead, halide perovskite nanocrystals is essential for the optimization of stability of these emerging materials-in applications such as solar cells) photodetectors, and light-emitting devices. We use magneto-photolurninescence spectroscopy of individual perovskite,CsPbBr3 nanocrystals as a unique, tool to determine their crystal structure, which imprints distinct signatures in the excitonic: sublevels of charge complexes at low temperatures. At zero magnetic field, the :identification of. two classes of photoluminescence spectra, displaying, either two or three sublevels in their exciton fine structure, shows evidence for existence of two-crystalline structures, namely tetragonal D-4h and orthorhombic D-2h,phases. Magnetic field shifts, splitting, and coupling of the subleveli provide a determination of the diamagnetic coefficient and valuable :information; on the exciton g-factor and its anisotropic character. Moreover, this.,. spectroscopic study reveals the optical properties of charged excitons and allows the extraction of the electron and hole g-factors for perovskite systems.