Fluoride ligand exchange for quantum dot light-emitting diodes with improved efficiency and stability

The ligands of quantum dots (QDs) not only play an important role in dispersion of the QDs in solvents and the protection of the QDs but could also block carrier injection into the QDs. Therefore, ligand engineering is important for improving performances of QD light-emitting diode (QLED) displays. In particular, exchange of an organic ligand with inorganic ones such as halides is expected to enhance efficiency and stability of QLED devices. In this study, an organic ligand on CdSe/ZnS QDs was exchanged with F− ligand in a non-polar solvent, which is suitable for device fabrication. As a result, stability of the QDs was improved, while the processability of QLED devices was maintained. Both external quantum efficiency of electroluminescence and device lifetime were improved, mainly because the thinner ligand layer improved the carrier injection efficiency.