Excitonic Properties in CdS/ZnS Core–Shell Nanocrystals

In this paper we propose to investigate theoretically the size dependent excitonic properties in a CdS/ZnS core–shell shaped semiconductor quantum dot. We calculated the electronic and exciton energy levels under the effective mass approximation by solving a three dimensional Schrödinger equation. We calculated also the exciton binding energy as well as the ground state exciton oscillator strength in the CdS/ZnS heterostructure. The variation of the system size parameters namely, the core radius and the shell thickness, showed that the excitonic properties are very sensitive to this variation. It is clearly found that the exciton energy spectrum changes significantly when varying the nanocrystal size. The binding energy and the oscillator strength can be also tuned by changing this parameter. Hence our numerical results showed that the quantum dot size is a decisive factor that enhances the excitonic properties in this confined system. These theoretical results could be crucial as they could be able to explain well the different photoluminescence spectra of quantum dot excitons, and simulate the behaviour of these excitonic properties versus the size variation.