Intense Dark Exciton Emission from Strongly Quantum-Confined CsPbBr<sub>3</sub> Nanocrystals
Daniel Rossi, Xiaohan Liu, Yangjin Lee, Mohit Khurana, Joseph Puthenpurayil, Kwanpyo Kim, А. В. Акимов, Jinwoo Cheon, Dong Hee Son
Abstract
Dark exciton as the lowest-energy (ground) exciton state in metal halide perovskite nanocrystals is a subject of much interest. This is because the superior performance of perovskites as the photon source combined with long lifetime of dark exciton can be attractive for many applications of exciton. However, the direct observation of the intense and long-lived dark exciton emission, indicating facile access to dark ground exciton state, has remained elusive. Here, we report the intense photoluminescence from dark exciton with microsecond lifetime in strongly confined CsPbBr 3 nanocrystals and reveal the crucial role of confinement in accessing the dark ground exciton state. This study establishes the potential of strongly quantum-confined perovskite nanostructures as the excellent platform to harvest the benefits of extremely long-lived dark exciton.