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 allowed for the development of
very efficient quantum dot lasing [1] and the understanding of blinking
dynamics [2], while charge transfer management has yielded single quantum dot
LEDs [3], LEDs with reduced efficiency roll-off [4], and enabled studies of
carrier and spin dynamics [5]. 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 control of intensity blinking, as well
as 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, all 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.