Blinking of CdSe/Cd.33Zn.67S semiconductor nanoplatelets

Abstract

Unstable photoluminescence quantum yield is important because it indicates changes in the transition rates between excited states. We synthesized 4.5 monolayer CdSe core, Cd.33Zn.67S gradient shell semiconductor nanoplatelets. The platelets exhibit a variety of blinking behaviors. Change points in the brightness of the platelets were investigated with frequentist and Bayesian techniques. We measured blinking power law constants ranging from 1.4 to 2.3. The brightness levels of blinking quantum particles are important because they are an accessible, if ambiguous, way to study surface photochemistry. Using histograms and a clustering algorithm, we determined that the number of brightness levels in the nanoplatelets is in the range of two to nine, with the lower end of that range appearing most likely and common. We conclude that the thickness and ensemble spectra are insufficient information to understand the evolving coupling between the excited states of platelets. Models of the interplay of excited state localization and reaction kinetics that span 10−10m to 10−8m and 10−10s to 102s are needed.