Effect of a buffer layer between the shell and ligand on the optical properties of an exciton and biexciton in type-II quantum dot nanocrystals

Abstract

In this study, we have investigated the effect of the buffer layers on the electronic and optical properties of an exciton (X) and a biexciton (XX) in a type-II CdTe/CdSe quantum dot nanocrystal. In an experimental study, it has been reported that when a CdTe/CdSe quantum dot nanocrystal is coated by a ZnTe material as a buffer layer, the photoluminescence quantum yield is growing from 4 to 20%. We have confirmed theoretically this improvement and extended the calculations to an XX structure. In the calculations, two different semiconductor materials, CdS and ZnTe, have been considered for the buffer layer. We have theoretically shown that the buffer layer causes an increase in the radiative oscillator strength of both X and XX. When the ZnTe is used as the buffer layer, the oscillator strength becomes stronger when compared to CdSe buffer material because of higher conduction band offset between CdSe and ZnTe.

Keywords:

• Quantum dot
• type-II nanocrystals
• multi-exciton in nanocrystals

Acknowledgements

MS thanks Abdullah Gul University Foundation (AGUV) for their partial financial support.

Notes

No potential conflict of interest was reported by the authors.

This work is a part of the MSc degree thesis prepared by F. Koç at Physics Department of Selcuk University.

Additional information

Funding

This work was supported by the TUBITAK TBAG [project number 109T729].