Temporal Dynamics of Exciton and Recombination Luminescence in CdTe/SiO₂ (Core/Shell) Quantum Dots

In this paper, we report a study of the temporal dynamics of photoluminescence intensity in cadmium telluride quantum dots coated with a silicon dioxide shell under continuous optical illumination. Our results demonstrate that at least two mechanisms influence emission from CdTe/SiO₂ quantum dots. In the early stages of our experiments, the luminescence intensity in CdTe/SiO₂ quantum dots is observed to rise, whereas in the final stage luminescence photodegradation begins to prevail. The former mechanism, related to photoenhancement, is due to passivation of surface defects by water molecules and a decrease in the number of nonradiative recombination centers. The latter mechanism, related to photodegradation, can be accounted for by the photooxidation of the CdTe core under the effect of oxygen.