Blinking statistics in single semiconductor nanocrystal quantum dots

Statistical studies of fluorescence intermittency in single CdSe nanocrystal quantum dots (QD's) reveal a temperature-independent power-law distribution in the histogram of on and off times---the time periods before the QD turns from emitting to nonemitting (bright to dark) and vice versa. Every QD shows a similar power-law behavior for the off-time distribution regardless of temperature, excitation intensity, surface morphology or size. We propose a dynamic model of tunneling between core and trapped charged states to explain the universal power-law statistics of the blinking events observed. The on-time probability distributions show evidence of both a tunneling mechanism similar to the off-time statistics and a secondary, photoinduced process that leads to a truncation of the power law. The same blinking statistics are also observed for single CdTe nanocrystal QD's.