Stable Blue Quantum Dot LED with 23% external quantum efficiency

Abstract The efficiency and stability of red and green quantum dot light-emitting diodes (QD-LEDs) have already met the requirements for displays. However, the performances of blue QD-LEDs, particularly pure blue QD-LEDs, are far inferior to that of their counterparts, hindering the commercialization of full-color QD-LED technology. Severe electron and hole accumulation at the hole transport layer (HTL) and quantum dot (QD) interface are the causes of efficiency loss and poor stability. Here, we propose inserting a protective layer (PBO (Poly-p-phenylene benzobisoxazole)) between the HTL and QD layer to suppress the accumulation of electrons and holes at the HTL/QD interface, reducing electron leakage and alleviating the damage to the HTL. This strategy enables us to achieve a record peak external quantum efficiency (EQE) of up to 23% and a record T 50 operational lifetime of more than 41000 h with an initial brightness of 100 cd m -2 in pure blue QD-LEDs (emitting at 458 nm). The mitigated electron and hole accumulation at the HTL/QD interface is confirmed by capacitance-voltage characteristics and electro-absorption spectra.