Highly Stable Red Quantum Dot Light Emitting Diodes with Long T95 Operation Lifetime.

Quantum dot light-emitting diodes (QLEDs) with excellent performances such as brightness, external quantum efficiency (EQE) and lifetime have almost met the requirement of low brightness display. However, the short operation lifetime under high brightness limits the application of QLEDs in outdoor displays and lightings. Herein, we report a highly efficient, stable red QLED device by using of lithium and magnesium co-doped as well as magnesium oxide shell-coated zinc oxide nanoparticle layer as electron transport layer (ETL). The optimized red QLED device has a high peak EQE of 20.6 %, a low efficiency roll-off at high current, and a remarkably long lifetime T95 > 11000 h at 1000 cd m-2, which indicates the realization of the most stable red QLED up to now. The improvement in the long-term stability of the red QLED is attributed to the use of co-doped and shell-coated zinc oxide ETL with reduced electron injection to improve the charge balance in QLED. The present work represents a huge step forward in realizing QLEDs for high-brightness display and lighting applications.