Band gap tailoring and photoluminescence performance of CdS quantum dots for white LED applications: influence of Ba²⁺ and Zn²⁺ ions

Abstract

Cadmium sulfide (CdS) is a suitable candidate in the II–VI wide band gap semiconductor family with robust applications in imaging, optical and optoelectronic fields. In the present investigations, various studies have shown that Ba²⁺ and Zn²⁺ ions are well incorporated in the CdS crystal structure without changing the original structure. The particle size was increased slightly as a function of Ba²⁺ concentration and the reason for this change was ascertained to the change in ionic radius of the Ba²⁺ and Cd²⁺ ions. UV–vis spectral studies showed that the absorption intensity was increased more due to the addition of Ba²⁺ ions and thereby the optical band gap has undergone a red-shift. This band gap narrowing occurrence was ascertained to the quantum confinement effect. The photoluminescence (PL) emission peaks were observed at 384 nm (UV region), 483 nm (blue), 523 nm (green), and 685 nm (red). The Ba²⁺ ion (2 wt. %) incorporation into Zn:CdS crystal structure showed an excellent optical property and offered various color emissions with high intensity. The primary studies (XRD, SEM) confirmed the crystalline nature and surface morphological information of the samples. The elemental and compositional analysis were made using EDX and FTIR results and they verified the purity of the synthesized nanomaterials. As the composition of Ba²⁺ and Zn²⁺ ion-incorporated CdS can be successfully prepared using facile co-precipitation method without using a capping agent, which possesses good absorption in UV region and offers an opportunity to tune the PL emission, these materials can be selected for the solar cells and white LED applications.