Stable and efficient QLEDs with crystallographic TiO_2 as the electron transportation layer and improved carrier transportation by chlorination

摘要

In order to obtain improvement in efficiency and stability of quantum dot light-emitting diodes (QLEDs), it is essential to seek carrier transport layer with higher carrier transport efficiency and better air stability. In terms of the high-performance carrier transport layer, solution-processed inorganic metal oxides show promise for efficient QLEDs because of their suitable energy band, high carrier mobility, especially their outstanding air stability. In this study, we employed high-quality oleic acid-capped TiO_2 nanocrystals as the electron transportation layer to fabricate air-stable inverted QLEDs. These TiO_2 nanocrystals have narrow size distribution, outstanding crystalline property, especially excellent air stability. To improve the interfacial carrier transportation performance of oleic acid-capped TiO_2 nanocrystals, we introduce a thionyl chloride (SOCl_2) post-ligand exchange process that replaces organic long-chain ligands with single inorganic ligands efficiently. The stability of oleic acid-capped TiO_2-based QLEDs were evaluated by comparing with the traditional ZnO-based QLEDs. As a result, oleic acid-capped TiO_2 nanoparticles show excellent long-term air stability. This study offers an alternative strategy to deal with the stability issue of optoelectronic devices.