High Efficiency All-Solution-Processed Inverted Quantum-Dot Light-Emitting Diodes

Abstract

Inverted quantum dot (QD) light-emitting diodes (QLEDs) offer a cost-effective solution for active matrix-driven displays. However, solvent erosion compromises the structural integrity of the QD emission layer (EML) and introduces interfacial defects, leading to significant degradation in the light emission and charge-injection efficiency of fully solution-processed inverted QLED devices. In this study, this issue was addressed by introducing a polyethylenimine (PEIE) layer between the hole transport layer (HTL) and the EML. The PEIE layer effectively prevents solvent-induced damage to the underlying QD layer and reduces leakage current by decreased interfacial defects, thereby enhancing effective charge-injection and improving device efficiency. Furthermore, the combination of poly [bis(4-phenyl)(4-butylphenyl)amine] (Poly-TPD) and phosphomolybdic acid hydrate (PMAH) as transport layers substantially enhances the brightness and efficiency of the device. As a result, the optimized inverted QLEDs achieved a record external quantum efficiency (EQE) of approximately 23.2%, a current efficiency (CE) of 41.2 cd A^–1, and well-controlled efficiency roll-off. The study systematically explored the impact of different interlayer materials and their positions on device performance, highlighting the importance of interface engineering in optimizing charge-injection and transport.