Energy-band diagrams illustrating the dynamics of electron-hole pairs in blinking quantum dots. (a) Physical processes in quantum dot blinking: g: generation rate, kr: recombination rate constant, kA : rate constant for Auger recombination, kt: trapping rate constant, kd: detrapping rate constant, knrt: rate constant for non- radiative recombination. (b) Auger recombination in quantum dots. Band-to-band recombination is coupled with excitation of a charge carrier (in this case a hole) that quickly relaxes (on the order of picoseconds) back to the band edge.

Energy-band diagrams illustrating the dynamics
of electron-hole pairs in blinking quantum dots.

Under constant illumination, a single quantum dot (QD) is blinking (intermittent fluorescence). This would greatly limit the application of using a single quantum dot in particle tracking, as well as in lasing technology.

QD blinking is characterized by switching between an “on” state and an “off” state, and a power-law distribution of on and off times with exponents from 1.0 to 2.0. The origin of blinking behavior in QDs, however, has remained a mystery.

 

In this research, we developed a theoretical model in which by studying the interaction between photons and single quantum dot (QD), we were able to explain almost all the characteristics of blinking, including under what condition non-blinking occurs, what results in grey state, as well as the power-law behavior.

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