Effect of dithiocarbamate chelate ligands on the optical properties of InP/ZnS quantum dots and their display devices

The optical properties of colloidal quantum dots (QDs), which show unique luminescent properties in comparison with bulk materials, are generally dependent on the size of the core and shell of the QD, but are also significantly affected by ligands attached to the QD's surface. In this study, we investigated not only the effect of ligand substitution on the optical properties of the QD itself but also the QD-light emitting diode (QD-LED) in which the QD was embeded as a light-emitting material. The monodentate amine ligands of InP/ZnS QDs were replaced by bidentate dithiocarbamate (DTC) chelate ligands capable of imparting delocalization property to the surface of InP/ZnS QDs. 1H NMR spectrum showed that the native ligands were partially exchanged with the DTC ligands. Photoluminescence (PL) spectra before and after ligand substitution show a bathochromic shift of about 10–25 nm depending on the electrical resonant properties of the DTC ligands. The QD-LED device was fabricated using QDs replaced by DTC ligands, and some improvements in device properties were observed. Here, we first report the ligand dependence of the photo- and the electroluminescence of InP/ZnS QDs in solution and device.