Chlorine-Modified Low-Temperature Crystallized TiO ₂ Electron Transport Layer for Stable QLEDs

Titanium dioxide (TiO2) is a promising alternative to conventional zinc oxide (ZnO) electron transport layers (ETLs) in quantum dot light-emitting diodes (QLEDs) owing to its superior chemical stability. However, TiO2 ETLs fabricated via conventional high-temperature pyrolysis often suffer from inadequate crystallinity and high injection barrier, consequently leading to low electron injection efficiency. Herein, an efficient TiO2 ETL was achieved via chlorine modified low-temperature synthesized anatase TiO2 colloidal nanoparticles (NPs). Highly crystalline TiO2 NPs ensure excellent electrical conductivity, while chlorine modification effectively suppresses nonradiative recombination at the TiO2/QD interface and reduces the electron injection barrier. QLEDs incorporating a Cl-TiO2 ETL achieve a 39.5% improvement in current efficiency and a 64.8% extension in T50 lifetime over the devices using pristine TiO2. Moreover, Cl-TiO2 demonstrates superior atmospheric stability over ZnO as an ETL in QLEDs. This work offers a practical strategy for the development of high-performance and operationally stable QLEDs.