Synthesis and characterization of CdS/ZnS heterostructures to improve the optical properties of CdS quantum dots

Abstract

In this work, we performed the synthesis of CdS quantum dots (QDs) and CdS/ZnS heterostructures (HQDs) via a hot injection method. The chemical route influenced the growth control and the physicochemical stability of the QDs with great reproducibility. To better understand the optoelectronic properties of CdS QDs and CdS/ZnS HQDs, we studied their surface states by means of UV–Vis assays and evaluated the emission peaks of each state, thus determining the band gap energy, nanoparticle average size, photoluminescence with temperature variation, and decay rate. Our results suggest an improvement of the optical properties as indicated by the PLQY of up to 64% for encapsulated samples, showing the efficiency of the process performed. The improvement is also supported by an intensity reduction of emissions from surface defects and vacancy states, and an intensity increase of the excitonic transitions and decreasing in the mean lifetime of luminescence for all HQDs samples.