ABSTRACT
In this chapter, we review recent experimental work investigating various aspects of single CdSe and CdTe colloidal quantum dot (QD) optical dynamics. The simple yet powerful technique of far field microscopy allows access to optical properties that are immeasurable from ensemble studies. These include dramatic switching on and off of the emission intensity and fluctuating emission energy in continuous and discrete shifts that occur in a large range of timescales. By simultaneously measuring the changes in the emission frequency and intensity of a large number of QDs, we uncover evidence of complex mechanisms entangling the fluorescence intermittency with the spectral shifting. In addition, statistical studies of fluorescence intermittency reveal that histograms of on-and off-times—the time periods before the QD turns from emitting to nonemitting (bright to dark) and vice versa—follow a power-law distribution. Based on this power-law behavior, the blinking mechanism can be understood in a unifying, dynamic model of tunneling between core and trapped charged states. Furthermore, variations in the blinking rate due to temperature, 216excitation intensity, and surface overcoating changes are explained via a secondary, photoinduced process that limits the longer on durations. These studies offer a glance into the capacity of single QD spectroscopy in unraveling the intricacies of single semiconductor QD optical dynamics.
