Utilizing a compact diamino-based ligand as a charge balancer in quantum dot light-emitting diodes

Charge imbalance within the emissive layer (EML) has been identified as a major obstacle to achieving high-performance quantum dot light-emitting diodes (QD-LEDs). To address this issue, we propose the use of a compact diamino-based ligand as a universal approach to improve the charge balance within the QD EML. Specifically, we treat QDs symmetrically with 1,4-diaminobutane (DAB) on both the bottom and top sides. This treatment simultaneously modulates the injection properties of electrons and holes, effectively suppressing electron injection into QDs while facilitating hole injection. As a result, QD-LEDs with symmetrical DAB treatment exhibit a 1.5-fold increase in external quantum efficiency and a remarkable 4.5-fold increase in device lifetime. These results highlight the role of the compact diamine-based ligands as highly efficient charge balancers to realize high-performance and highly stable QD-LEDs.