Correlation between photoluminescence intermittency of CdSe quantum dots and self-trapped states in dielectric media

Abstract

We present evidence that the photoluminescence intermittency of $\mathrm{Cd}\mathrm{Se}∕\mathrm{Zn}\mathrm{S}$ core/shell quantum dots is correlated with the dielectric environment surrounding the quantum dots. The statistics of dark state lifetimes in the intermittency is found to be related to the stabilization energy of charges in the local dielectric surrounding of the quantum dot. This supports the model of an ionized quantum dot in the dark state. Charges ejected from the quantum dot are suggested to be self-trapped in mid-bandgap states of the surrounding matrix due to atomic and electronic relaxation processes. These trap states are inherent to disordered materials and proposed to be a general source of power law intermittency of various types of emitters such as quantum dots and dye molecules.