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Colloidal lead halide perovskite (LHP) nanocrystals (NCs), with bright and spectrally
narrow photoluminescence (PL) tunable over the entire visible spectral range, are of
immense interest as classical and quantum light sources. The brightness of an emitter is
ultimately described by Fermi’s golden rule. We present a record-low sub-100 ps
radiative decay time for CsPb(Br/Cl) 3 NCs, almost as short as the reported exciton
coherence time, by the NC size increase to 30 nm. The characteristic dependence of
radiative rates on QD size, composition, and temperature suggests the formation of
giant transition dipoles, as confirmed by effective-mass calculations for the case of the
giant oscillator strength. Importantly, the fast radiative rate is achieved along with the
single-photon emission despite the NC size being ten times larger than the exciton Bohr
radius. NC self-assembly is a versatile platform collective phenomena with perovskite
NCs, such as superfluorescence in multicomponent perovskite NC superlattices [2]. We
also present all-perovskite binary nanocrystal superlattices [3], exhibiting interaction
between the strongly and weakly confined perovskite QDs by means of energy transfer. |