Synthesis of Highly DispersibleTiO2 Nanoparticles and Their Application in Quantum Dot Light Emitting Diodes

Metal oxide nanoparticles are commonly used as electron transport layers (ETLs) in quantum dot light emitting diodes (QLEDs) because of their wide band gap, high electron mobility, and appropriate conduction and valence band positions. Currently, ZnO nanoparticles are the most successfully electron transportation material in high-performance QLEDs. However, the positive aging effect is widely observed for ZnO-based QLEDs since the amphiprotic ZnO nanoparticles are not stable under the acidic, basic, and moisture conditions, which limits their applications. In this study, highly dispersible and alcohol-soluble TiO₂ nanoparticles are synthesized by using a non-hydrolytic sol-gel method, followed by a dimethyl sulfoxide post-treatment. The use of colloidal TiO₂ nanoparticles as an ETL yields optimal QLED, with a maximum external quantum efficiency of 12.03%, a highest luminance of 103,420 cd/m², and a current efficiency of 18.06 cd/A. These results reveal that TiO₂ nanoparticles hold great potential as ETL in the future QLEDs.