Versatile Use of 1,12-Diaminododecane as an Efficient Charge Balancer for High-Performance Quantum-Dot Light-Emitting Diodes

Balancing the charge injection rates in the emissive layer (EML) is a key factor in achieving high-performance quantum-dot light-emitting diodes (QD-LEDs). This has mostly been pursued by controlling the injection rate of one type of charge carrier (typically electrons). Simultaneous engineering of both types of charge carriers, however, would be more efficient in achieving the desired charge balance within a device. Herein, the versatile use of 1,12-diaminododecane (DAD) ligands is proposed to achieve balanced charge injection rates into the QD EML, thereby enhancing QD-LED performance. By utilizing the dipole moment and short chain lengths, DAD ligands function as efficient electron retarders and hole boosters. Specifically, DAD treatment on the surface of zinc oxide generates an electronic barrier to QDs. Meanwhile, DAD treatment on the surface of the QDs reduces the potential difference between the organic hole transport layers and QDs. Consequently, the QD-LEDs with the adoption of DAD at the two different positions exhibit balanced charge injection rates into the QDs, enhancing device efficiency and operational stability. The present study proposes a simple yet efficient chemical method that controls both electron and hole injection properties to achieve high-performance QD-LEDs.