Regulation on Dual Interfaces of QD with ETL and HTL by Guanidine‐Based Ligands Enable High‐Performance Blue Quantum Dot Light‐Emitting Diodes with 24.3% External Quantum Efficiency

The poor efficiency and stability of blue quantum dot light-emitting diodes (QLED) hinder its practical applications in full-color displays. Insufficient hole injection and excessive surface defects in quantum dots (QD) layer remain the primary challenges limiting the performance of blue devices. Herein, a dual interface modification strategy is proposed to enhance the performance of blue QLED by synergistically regulating both the electronic transport layer (ETL)/QD and hole transport layer (HTL) HTL/QD interfaces. At the HTL/QD interface, the introduction of guanidine sulfamate (GAS) ligands passivates QD surface defects while reducing the hole injection barrier, thereby improving hole injection efficiency in the low-bias region. Meanwhile, at the QD/ETL interface, Guanidine chloride (GACl) ligands are incorporated to passivate interfacial defects, suppress leakage current, and suppress excessive electron injection, thus enhancing hole transport efficiency within the QDs layer. The synergistic effect of bilateral GA-based ligands can simultaneously enhance the hole injection efficiency based upon improving the hole transport efficiency, significantly increasing the radiative recombination ratio during device operation. As a result, the dual-ligand modified blue QLEDs achieve a remarkable improvement in external quantum efficiency (EQE) from 16.6% to 24.3%, and a sevenfold enhancement in operational lifetime.