Effect of Electrostatic Interactions on the Photophysical Properties of the Composites of CdTe Nanocrystals and Carbazole-Containing Polymers

Abstract

We demonstrated in this study that the electrostatic interaction between nanocrystals (NCs) and polymers was dominant in the photophysical properties of their composites. This effect became more pronounced under illumination and in the presence of the carbazole moieties. The mechanism in which carbazole moieties influenced the PL properties was systematically investigated by means of steady-state fluorescence, fluorescence lifetimes, and ESR spectra. Our experimental results showed that the electrostatic interactions between CdTe NCs and polymers brought defects on the surface of NCs and hence led to the involvement of surface states in the carrier recombination process. Therefore, the composites were inclined to be oxidized when their net charges were slightly positive or negative. The optimal light emitting ratio of NCs to polymers was at the threshold point that NCs could be just completely transferred from the aqueous phase to the organic phase because the composite exhibited nearly electric neutrality at such a ratio. On the other hand, carbazole moieties had an important influence on the intrinsic recombination process of the CdTe NC's core states due to efficient electron transfer at the interface of the NCs and polymers.