Efficient red phosphorescence polymer light-emitting diodes with dual function polymer

The efficient red phosphorescence polymer light-emitting diodes (PLEDs) based on aluminum (Al) cathode were demonstrated. The devices composed of neutral aminoalkyl substituted polyfluorene, poly[(9,9-bis(3′-(N,N-dimethylamino)propyl)-2,7-fluorene)-alt-2,7-(9,9-dioctylfluorene)] (PFN) as the host and bis(1-(3-(9,9-dimethyl-fluorene-2-yl)phenyl)isoquinoline-C2,N′) iridium (III) (3-(pyridin-2′-yl)-1,2,4-triazole) [Ir(DMFPQ)2pt] as the dopant. High external quantum efficiency of 5.6% (at 16.8 V) and a luminance of 1400 cd/m2 (at 19.6 V) were obtained from the device with Al cathode only. The performances (quantum efficiency and luminance) of the devices could be comparable to those of the devices with a low work-function metal cathode (such as calcium and barium). We believe that the reason for the high performances was due to the effective electron injection from Al into PFN.