Dipole Ligands Modification of Blue Quantum Dots for High-Performance Light-Emitting Diodes

The electroluminescence of quantum dot (QD) light-emitting diodes (QLEDs) has undergone significant enhancement to fulfil the prerequisites for commercialization in next-generation display. Nevertheless, the blue QLEDs still suffer from subpar device performance compared to red and green counterparts. The deep energy level of blue QDs leads to inferior hole injection capability. Additionally, the small potential barrier between the core and shell facilitates carrier in blue QDs coupling with sulfur dangling bonds on the QD surface. Herein, phenethylammonium chloride (PEACl), a dipole molecule, is introduced to modify the surface of blue QDs. The replacement of long-chain oleic acid ligands with Cl^- ions improves carrier transport, while the NH₃⁺ group of PEACl passivates surface sulfur defects. Additionally, the large dipole moment of PEACl upshifts the energy levels, thereby enhancing hole injection efficiency in the devices. Consequently, the resulting devices based on PEACl-modified ZnCdSe/ZnCdS/ZnS QDs exhibit a record external quantum efficiency of 23.8%, a peak luminance of 42,724 cd m⁻², and an extrapolated operational lifetime of 22,180 h at 100 cd m⁻², significantly outperforming the control devices. This work offers a promising approach to enhance the efficiency and stability of blue QLEDs for advanced display applications.