Molecular dipole interfacial engineering for high-performance quantum-dot light-emitting diodes†

Balancing carrier injection via improving hole injection capability plays a key role in high-performance quantum dot light-emitting diodes (QLEDs). Herein, a self-assembled monolayer of carbazole-based derivatives is utilized to construct a dipole functional layer at the interface between the hole transport layer (HTL) and quantum dots (QDs) to facilitate hole injection. Additionally, rational interface engineering significantly reduces the trap-state density because of the highly ordered molecular arrangement. The resultant QLEDs present the promising maximum external quantum efficiency (EQE) of 25.03%, which is remarkably higher than that of the control ones (20.58%). The optimized device shows outstanding stability and a long operation lifetime (T₉₅ lifetime at 1000 cd m⁻², 14 695 h) in the air. This simple strategy presents how to increase hole injection by constructing a dipole interface and optimizing molecular arrangement to improve the performance of QLEDs.