High efficiency red phosphorescent organic light-emitting diodes with single layer structure

We report simple red phosphorescent devices comprising single layer configuration using a tris[1-phenylisoqunolinato-C2,N]iridium (III) (Ir(piq)3) dopant concentration as low as 1 wt.% in mixed host systems. The driving voltage of 5.4 V to reach the brightness of 1000 cd/m2 in the mixed emitting layer of N,N′-diphenyl-N,N′-bis(1,1′-biphenyl)-4,4′-diamine (NPB) and bis(10-hydroxybenzo[h]quinolinato)beryllium (Bebq2) is reported. Maximum current and power efficiency values of 9.44 cd/A and 10.62 lm/W are obtained in this single layer structure PHOLEDs, respectively. It is believed that the direct injection of charge carriers to the organic layer and high carrier mobility therein are the keys to the simplification of the device structure.