Two Mechanisms Determine Quantum Dot Blinking

Many potential applications of quantum dots (QDs) can only be realized once the luminescence from single nanocrystals is understood. These applications include the development of quantum logic devices, single photon sources, long-life LEDs, and single molecule biolabels. At the singlenanocrystal level, random fluctuations in the QD photo-luminescence (PL) occur, a phenomenon termed blinking. There are two competing models to explain this blinking: Auger recombination and surface trap induced recombination. Here we use lifetime scaling on core-shell NCs with close to unity quantum yield to demonstrate that both types of blinking occur in the same QDs.

We prove that Auger-blinking can yield exponential on/off times in contrast to earlier work. The surface passivation strategy determines which blinking mechanism dominates. This study unifies earlier studies on blinking mechanisms and provides direct evidence that stable single QDs can be engineered for optoelectronic applications.