Optimized Performances of Thick Film Organic Lighting-Emitting Diodes

The performance of organic light-emitting diodes (OLEDs) with thick film is optimized. The alternative vanadium oxide (V2O5) and N,N'-di(naphthalene-1-yl)-N,N'-diphenyl-benzidine (NPB) layers are used to enhance holes in the emissive region, and 4,7-dipheny-1,10-phenanthroline (Bphen) doped 8-tris-hydroxyquinoline aluminium (Alq(3)) is used to enhance electrons in the emissive region, thus ITO/V2O5 (8 nm)/NPB (52 nm)/V2O5 (8 nm)/NPB (52 nm)/Alq(3) (30 and 45 nm)/Alq(3):Bphen (30 wt%, 30 and 45 nm)/LiF (1 nm)/Al (120 nm) devices are fabricated. The thick-film devices show the turn-on voltage of about 3 V and the maximal power efficiency of 4.5lm/W, which is 1.46 times higher than the conventional thin-film OLEDs.