Optimization of a poly(p-phenylene benzobisoxazole)-based light-emitting device with a complex cathode structure

In this work, we report the preparation of a series of electroluminescent (EL) devices based on a high-performance polymer, poly(p-phenylene benzobisoxazole) (PBO), and their optoelectronic properties, which have been rarely explored. The device structure is optimised using a complex cathode structure of tris-(8-hydoxyquinoline) aluminium (Alq₃)/LiF/Al. By tuning the thickness of the Alq₃ layer, we improve the device efficiency dramatically in an optimized condition. Further analysis reveals that the Alq₃ layer in the complex cathode structure acts as a hole blocker in addition to its electron-injection role. A green light emission with a maximum brightness of 8.7 × 10³ cd/m² and a moderate current efficiency of 4.8 cd/A is obtained. These values are the highest ever reported for PBO devices. The high operational stability demonstrated by the present device makes it a promising tool for display and lighting applications. A new material is added to the selection of polymers used in this field up to now