Sub-Bandgap Optical Modulation of Quantum Dot Blinking Statistics

Abstract

Colloidal quantum dots (QDs) suffer from pervasive photoluminescence intermittency that frustrates applications and correlates with irreversible photodegradation. In single-QD spectroscopies, blinking manifests as sporadic switching between ON and OFF states without a characteristic time scale, and the longstanding search for mechanisms has been recently accelerated by techniques to controllably modulate the QD environment. Here, we develop an all-optical modulation scheme and demonstrate that sub-bandgap light tuned to the stimulated emission transition perturbs the blinking statistics of individual CdSe/ZnS core/shell QDs. Resonant optical modulation progressively suppresses long-duration ON events, quantified by a power-law slope that is more negative on average (Δα ON = 0.46 ± 0.09), while OFF distributions and truncation times are unaffected. This characteristic effect is robust to choices in background subtraction and statistical analysis but supports mechanistic descriptions beyond first-order kinetics. This demonstration of all-optical perturbation of QD blinking dynamics provides an experimental avenue to disentangle the complex photophysics of photoluminescence intermittency.

Evidence for Two Time Scale-Specific Blinking Mechanisms in Room-Temperature Single Nanoplatelets

“…While the trapped exciton persists, Auger recombination competes with emission and increases the proportion of the off time in the blinking trajectory. There is experimental evidence for both types of blinking mechanisms in semiconductor nanocrystals; in fact, they may operate simultaneously. − …”

Unconventional Blinking Characteristics of Single Quantum Dots Revealed by Timing Analyses

“…Intensity binning made a huge success in the early endeavors of revealing the complex temporal nature of single QD blinking, and the power-law analysis remains popular among researchers. 15 Because of its popularity, the limitations and drawbacks of intensity binning should be considered with particular caution. First and most obviously, the choice of binning and thresholding could create artifacts.…”

All-optical fluorescence blinking control in quantum dots with ultrafast mid-infrared pulses

“…As a manifestation of self-similarity behavior that is seen in the blinking of many types of fluorophores 3 , the power-law relationship is highly robust to external perturbations. 3,27,28 A previous study by Hasham et al 29 reported that a sub-bandgap CW laser can change the QD blinking power-law statistics by depleting excited states, resulting in more blinky QDs. In our experiments, we find that the MIR field depletes the OFF states and alters the OFF-time power-law statistics.…”