Ultrafast Dynamics of Self-Trapped Excitons in Lead-Free Perovskite Nanocrystals.

Lead-free halide perovskite nanocrystals (NCs) have received increasing attention owing to their low toxicity and high stability. Localized charge distribution and strong carrier-phonon coupling in lead-free perovskite NCs facilitates the formation of self-trapped excitons (STEs), which typically give a broadband photoluminescence (PL) emission with a large Stokes shift. In this Perspective, we highlight how PL modulations can give rise to an efficient white-light emission by understanding and tuning the ultrafast dynamics of STEs in lead-free perovskite NCs. We then present the exciton energy transfer mediated by STEs to provide an efficient thermally activated delayed fluorescence and dopant PL. We also illustrate promising directions for future applications based on STEs. We hope that this Perspective can provide a new viewpoint for researchers to understand the ultrafast dynamics of STEs and promote lead-free perovskite NCs for optoelectronic applications.