Efficient and Stable OLEDs with Inverted Device Structure Utilizing Solution-Processed ZnO-Based Electron Injection Layer

摘要

To realize low-cost, efficient, and stable organic light-emitting diodes (OLEDs)in future large area displays and lighting, the development of suitablesolution-processed functional materials is highly desirable. Herein, a series ofefficient and stable OLEDs with an inverted device architecture is reported,employing both a vapor-deposited phosphorescent aggregate emitter, i.e.,Pd(II) 7-(3-(pyridine-2-yl- N)phenoxy- C)(benzo- C)(cbenzo4,5imidazo- N)1,2-a1,5naphthyridine, and a solution-processed ZnO layer as potentialelectron injection layer and electron-transporting layer. One of the optimizedOLED devices exhibits its peak external quantum efficiency (EQE) of 23.9and retains EQEs of 23.5 and 18.7 at 1000 and 10 000 cd m~（?2）, with a lowefficiency roll-off. Such an efficient device also demonstrates a measuredlifetime (LT95) of 98.6 h with an initial brightness of 10 435 cd m~（?2）corresponding to an estimated LT95 of 5313 h at 1000 cd m~（?2）. By depositing a2 nm Al on the ZnO surface, an estimated LT95 at 1000 cd m~（?2） of such adevice can be further extended to 73 244 h, making it the longest-lived OLEDreported in the literature domain. This study lays the strong foundation for thefuture deployment of efficient and stable inverted OLEDs withsolution-processed ZnO layers for a wide range of displays and lightingapplications.