  The power conversion efficiency of photovoltaic devices based on
semiconductor perovskites has reached ~20% after just several years of research
efforts. With concomitant discoveries of other promising applications in
lasers, light-emitting diodes and photodetectors, it is natural to anticipate
what further excitements these exotic perovskites could bring about. Here we
report on the observation of single photon emission from single CsPbBr3
perovskite nanocrystals (NCs) synthesized from a facile colloidal approach.
Compared with traditional metal-chalcogenide NCs, these CsPbBr3 NCs exhibit
nearly two orders of magnitude increase in their absorption cross sections at
similar emission colors. Moreover, the radiative lifetime of CsPbBr3 NCs is
greatly shortened at both room and cryogenic temperatures to favor an extremely
fast output of single photons. The above findings have not only added a novel
member to the perovskite family for the integration into current optoelectronic
architectures, but also paved the way towards quantum-light applications of
single perovskite NCs in various quantum information processing schemes.
