  Colloidal semiconductor quantum dots (QDs) are excellent luminescent
nanomaterials for a broad range of optoelectronic applications. Their
photoluminescence blinking, however, hinders their practical use in many
aspects. It has been shown that coupling QDs to plasmonic nanostructures may
provide a viable way to suppress blinking. Nevertheless, the underlying
mechanism of blinking suppression remains unclear and debated. Here, by
deterministically coupling a single QD to a plasmonic nanocavity, we clarify
the mechanism of blinking suppression, and demonstrate unprecedentedly bright
emission from a single colloidal QD. In particular, we report for the first
time that the coupled system exhibits nonblinking photoluminescence with
blinking lifetime, which shows that the elimination of photoluminescence
blinking originates from enhanced quantum yield of the charged states. We
identify that the radiative decay rate is boosted from (48 ns)-1 to (0.7 ns)-1,
which outcompetes Auger processes and enables similar quantum yields for
charged and neutral excitons. Moreover, we demonstrate ultrabright
photoluminescence of up to 17 million detected photons per second from a single
QD. This work sheds new light on the goal of achieving ultrabright nonblinking
QDs and may benefit a variety of QD-based applications.
