Atomistic effect of internal and external shell on physical behaviours of InP/GaP/ZnS core/shell/shell nanocrystals: Empirical tight-binding theory

Abstract

By imposing the atomistic tight-binding theory in the conjunction with a configuration interaction description, the impact of the GaP internal and ZnS external growth shell on the greener InP/GaP core/shell and InP/GaP/ZnS core/shell/shell nanocrystals is theoretically carried out. Herein, the demonstration to control the structural and optical properties by engineering the thickness of the interior and exterior encapsulated shell is underlined. To theoretically analyze the influence of the terminated shell on the atomistic behaviours, I demonstrate single-particle spectra, optical band gaps, ground-state oscillation strengths, electron-hole interaction and excitonic splitting. The computations of InP/GaP core/shell and InP/GaP/ZnS core/shell/shell nanocrystals are sensitive with the internal and external growth shell. The reduction of the optical band gaps with the increasing internal and external growth shell thicknesses reflects the quantum confinement effect. The optical band gaps are tuned across the visible wave lengths from 515 nm to 775 nm by changing the internal and external growth shell thicknesses. Remarkably, termination of GaP internal and ZnS external shell on core and core/shell nanocrystals obviously improves the optical property, respectively. In addition, InP/GaP core/shell and InP/GaP/ZnS core/shell/shell nanocrystals with the large growth shell thickness can be probable to be a source of entangled photons. By means of the Stokes shift, InP/GaP core/shell and InP/GaP/ZnS core/shell/shell nanocrystals with a small growth shell thickness can be implemented as the optical filter. Based on the scientific research, this insight is important for the theoretical understanding and practical control by internal and external shell thicknesses, thus introducing a stepping-stone towards the commercialization of InP/GaP core/shell and InP/GaP/ZnS core/shell/shell nanocrystals.