Superfluorescence from Perovskite Quantum Dots

Inorganic lead halide perovskite quantum dots (QDs) exhibit extraordinarily bright emission and high oscillator strength due to their peculiar exciton fine-structure,¹ and very recently, revealed that single-photon superradiance further enhances their intrinsically strong light-matter interaction.² Moreover, we demonstrated that these quantum dots uniquely can be assembled to exhibit collective superfluorescent (SF) emission,^3,4 which requires excellent exciton coherence, and therefore, cryogenic temperatures and very low inhomogeneous broadening. Having recently extended this observation to various superlattices,^5,6 here we demonstrate that temperature and excitation density can drive the transition between superfluorescence and ASE regimes in a thin film of giant CsPbBr₃ perovskite QDs.⁷ At temperatures below 45 K, excitonic SF was observed, whereas above a transition range between 45 K and 100 K, ASE prevails but requires increased optical excitation and emitter density. Our results work out the different collective effects present in lead halide perovskites, providing fundamental insights into cooperative phenomena and important guidance for the development of compact and bright (quantum) light sources.