To Blink or Not to Blink? A New Criterion to Quantify Luminescence Blinking
Colloidal semiconductor quantum dots are promising materials for numerous applications due to their tunable emission and high quantum yields. However, emission instability in the form of luminescence blinking remains a significant obstacle to their practical implementation. While recent advances in synthesis and surface engineering have demonstrated partial or complete blinking suppression, the quantitative assessment of the "quality" of this suppression remains challenging. Existing criteria typically rely on threshold-based classification into ON and OFF states, which becomes inherently ambiguous owing to the continuous distribution of emission intensities in single quantum dots. Here, we propose a threshold-free two-dimensional quantitative criterion based on the variance of the recombination rate and the relative quantum yield, both of which can be extracted from standard time-correlated single-photon counting measurements. We validate the criterion using simulated blinking trajectories covering all major blinking mechanisms and demonstrate that it cleanly separates them into distinct regions of the two-dimensional parameter space while providing a quantitative measure of the degree of suppression. This approach directly quantifies the temporal stability of emission without requiring arbitrary state definitions, thereby providing a robust metric for comparing different blinking suppression strategies.