Pure Blue and Highly Luminescent Quantum-Dot Light-Emitting Diodes with Enhanced Electron Injection and Exciton Confinement via Partially Oxidized Aluminum Cathode

The balance injection of holes and electrons into a thin emissive quantum dot (QD) layer for efficient radiative recombination is critical to the color purity, stability, and efficiency of the QD-based light-emitting diodes (QD-LEDs). Due to the difficulty of charge injection into wide band gap blue QD layer, the performance of blue QD-LED is obviously inferior to the green and red counterparts. Here, high-performance ZnCdS/ZnS graded core/shell-based blue QD-LEDs with partial oxidized aluminum cathode (Al:Al₂O₃) via simple autoxidation are demonstrated. There is no any additional electron transport layer/hole transport layer involved in the device, which guarantees the color purity and simplifies the fabrication processes. Furthermore, the Al:Al₂O₃ cathode greatly enhances the charge injection and exciton recombination, rendering significant improvement in luminance and current efficiency compared with the control devices with Al or Alq3/Al electrodes. A record luminance of over 13 000 cd m⁻² has been achieved for blue QD-LEDs with Al:Al₂O₃ cathode. The findings of this study indicate that this simply processed and easily controlled autoxidation procedure is a promising strategy to achieve high-performance blue QD-LEDs.