Shell effects on the dielectric properties of core-shell quantum dots

The dielectric properties in semiconductor quantum dots are crucial for exciton formation, migration, and recombination. Different from 3D bulk materials, the dielectric response is, however, ambiguous for the small-sized 0D dots in which the effect of outer atoms on the inner atoms is usually described qualitatively. Based on the first-principles calculated electron density, the polarizability of the core-shell CdSe@ZnS wurtzite quantum dots is decomposed into the distributional contributions among which the dipole polarizability of the core is proposed to measure the shell effect on the dielectric properties of core-shell quantum dots. The shell thickness dependence on the shell effect is then studied, which is significant for the outermost shell but decays rapidly in the additional shells. Moreover, this model gives explicit physical origins of the core dipole polarizability in the core-shell QDs, which is determined by the intra-shell polarization and inter-core-shell charge transfer. Our study proposes a new approach for studying the dielectric properties of core-shell quantum dots, which is effective and extendable for other low-dimensional structures.

Automated summary

This article investigates the important role of dielectric properties in exciton formation, migration, and recombination in semiconductor quantum dots. Unlike 3D bulk materials, the dielectric response in small-sized 0D dots is usually described qualitatively. By decomposing the polarizability of the core-shell CdSe@ZnS wurtzite quantum dots based on first-principles calculations, the dipole polarizability of the core is proposed to measure the shell effect on the dielectric properties. The study also explores the dependence of the shell effect on shell thickness, finding that it is significant for the outermost shell but rapidly decays in additional shells. Furthermore, the model presented in this study provides a clear physical understanding of the core dipole polarizability in core-shell quantum dots, which is determined by intra-shell polarization and inter-core-shell charge transfer. This research proposes a new and effective approach for studying dielectric properties in core-shell quantum dots, which can be extended to other low-dimensional structures.