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At very low intensities, k$_{tr}$ determines the observed ‘off’ state decay rate and quantum yield. At higher intensities another exciton can be generated before the trapped charge recombines (with the rate k$_{nr}$ ), and Auger recombination becomes visible in the decay curve (see Fig. 4 b). At a low illumination intensity the ‘off’ QD cycles in a three step loop process including excitation, rapid trapping of a charge carrier and a relatively long nonradiative recombination process (left part of the picture in Fig. 4 b). When k$_{abs}$ is increased and becomes comparable to k$_{nr}$ , the QD shifts to the right part of the scheme in Fig. 4 b and the observed decay rate changes to k$_{Aug}$ . The relations between the decay rates mentioned above determine whether the ‘off’ state emission is dominated by trapping dynamics or by Auger dynamics at a given excitation rate. In particular, it is plausible that for some species of QDs the trapped charge recombination rate k$_{nr}$ is much smaller than for the CdSe/CdS/ZnS dots. This corresponds to an effectively long lived trap state, meaning that in the ‘off’ state under typical experimental conditions such QDs would only exhibit the Auger decay dynamics. 

The nature of the physical process responsible for the time dependence of k$_{tr}$ has yet to be investigated. Regardless of the origin of this process, it is clear that the above scheme of QD operation is inconsistent with physical models of QD blinking assuming that a charge must be trapped during the entire ‘off’ period. The experimental results seem to be consistent, however, with the model proposed by Frantsuzov and Marcus [14], wherein the random process responsible for the time variation of the trapping rate is the spectral diffusion of the 

