Colloidal semiconductor quantum dots; syntheses, properties and applications

The solution synthesis of colloidal semiconductor quantum dots (QDs), such as CdSe QDs, has developed tremendously in the last two decades. Such QDs exhibit excellent optical properties, such as size dependent optical gaps and efficient carrier multiplication, because of the quantum confinement effect. Colloidal QDs have potential in various optical and optoelectronic devices, such as light emitting devices, solar cells and wavelength converters for displays. The use of toxic cadmium materials in light emitting devices and wavelength converters is currently unavoidable for achieving full color visible emission. Less toxic alternatives are required. Safe facile procedures for synthesizing narrow gap arsenide QDs are also required for QD-solar cells, which exploit low threshold energies of carrier multiplication. This article reviews recent advances in the synthesis and properties of colloidal QDs. Their applications are reviewed in terms of cadmium-free QD-phosphors, and safe and facile syntheses of arsenide QDs for solar cells. Our group's research on the synthesis of the ternary chalcopyrite I-III-VI₂ semiconductors, ZnO and InAs QDs, and fabrication of electroluminescent devices using ZnO QDs is discussed.