Traditional quantum dots usually contain Cd elements, such as CdSe and CdTe quantum dots. These quantum dots show high luminous efficiency, but their application is limited due to their biological toxicity. In order to reduce the toxicity, many Cd-free quantum dots have been developed, among which ZnSe/ZnS quantum dots are an important type. ZnSe/ZnS quantum dots are core-shell type fluorescent quantum dots. In the structure of ZnSe/ZnS quantum dots, ZnSe is the core material and ZnS is the shell material. ZnS shell structure has lattice constant that can match with ZnSe core material, but the band gap is wider. As the shell, ZnS can effectively eliminate a large number of defects on the surface of ZnSe, and improve the luminescence performances. Due to the non-toxic and harmless properties of Zn element, ZnSe/ZnS quantum dots are a kind of green and environment-friendly quantum dots, and have attracted more and more attention in recent years.
Figure 1. Scheme of down shifting mechanism of ZnSe/ZnS QDs and proof-of-concept solar cell.
Figure 2. An example of ZnSe/ZnS quantum dots used in analysis and testing field.
According to the solubility, ZnSe/ZnS quantum dots can be divided into water-soluble ZnSe/ZnS quantum dots and non-water-soluble ZnSe/ZnS quantum dots.