Synthesis of highly dispersible TiO2 nanoparticles and their application in quantum dot light emitting diodes†

Abstract

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, nanoparticulate ZnO is the most successful electron transportation material in high-performance QLEDs. However, the positive aging effect is widely observed for ZnO-based QLEDs, as the instability of amphiprotic ZnO nanoparticles under acidic, basic, and moist conditions 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 QLEDs, with a maximum external quantum efficiency of 12.03%, a highest luminance value of 103 420 cd m⁻², and a current efficiency of 18.06 cd A⁻¹. These results reveal that TiO₂ nanoparticles hold great potential as ETLs in future QLEDs.