Enhanced electron injection and exciton confinement for pure blue quantum-dot light-emitting diodes by introducing partially oxidized aluminum cathode

Stable and efficient red (R), green (G), and blue (B) light sources based on solution-processed quantum dots (QDs) play important roles in next-generation displays and solid-state lighting technologies. The brightness and efficiency of blue QDs-based light-emitting diodes (LEDs) remain inferior to their red and green counterparts, due to the inherently unfavorable energy levels of different colors of light. To solve these problems, a device structure should be designed to balance the injection holes and electrons into the emissive QD layer. Herein, through a simple autoxidation strategy, pure blue QD-LEDs which are highly bright and efficient are demonstrated, with a structure of ITO/PEDOT:PSS/ Poly-TPD/QDs/Al:Al₂O₃. The autoxidized Al:Al₂O₃ cathode can effectively balance the injected charges and enhance radiative recombination without introducing an additional electron transport layer (ETL). As a result, high color-saturated blue QD-LEDs are achieved with a maximum luminance over 13,000 cd m^-2, and a maximum current efficiency of 1.15 cd A^-1. The easily controlled autoxidation procedure paves the way for achieving high-performance blue QD-LEDs.