  Electron transfer to an individual quantum dot promotes the formation of
charged excitons with enhanced recombination pathways and reduced lifetimes.
Excitons with only one or two extra charges have been observed and exploited
for very efficient lasing or single quantum dot LEDs. Here, by room-temperature
time-resolved experiments on individual giant-shell CdSe/CdS quantum dots, we
show the electrochemical formation of highly charged excitons containing more
than twelve electrons and one hole. We report the control over intensity
blinking, along with a deterministic manipulation of quantum dot photodynamics,
with an observed 210-fold increase of the decay rate, accompanied by 12-fold
decrease of the emission intensity, while preserving single-photon emission
characteristics. These results pave the way for deterministic control over the
charge state, and room-temperature decay-rate engineering for colloidal quantum
dot-based classical and quantum communication technologies.
