Superlattice-Induced Superfluorescence in Quasi-2D Metal Halide Perovskites

This paper reports the role of the superlattice (crystal) structure of the quasi-two-dimensional (2D) perovskite (PEA 2 (FAPbBr 3 ) n-1 PbBr 4 ) in room-temperature superfluorescence. Through steady-state and time-resolved spectroscopy, we observe a narrow spectral width, a quadratic emission dependence on the excitation fluence, and a burst of emission after a time delay in quasi-2D perovskite, key indicators of superfluorescence. Notably, bulk three-dimensional (3D) perovskite (FAPbBr 3 ) does not demonstrate these features, suggesting that the quasi-2D structure containing superlattices is a requirement for superfluorescence. The formation of superlattices in quasi-2D perovskite thin films was confirmed using scanning transmission electron microscopy (STEM). These results suggest that the search for new superfluorescent materials should prioritize exploring analogous materials with well-defined superlattice structures.