Effects of Co-Doping on the Red Fluorescent OLEDS

The device performance of red organic light-emitting diodes (OLEDs) was dramatically improved by co-doping of the red fluorescent material of (2Z, 2'Z)-3,3'-[4,4 ''-bis(dimethylamino)-1,1':4',1 ''-terphenyl-2',5'-diyl]-bis(2-phenylacrylonitrile) (ABCV-P) with the hole transport material of N'-bis-(1-naphyl)-N, N'-diphenyl-1,1'-biphenyl-4,4'-diamine (NPB) and the electron transport material of bis(2-methyl-8-quninolinato)-4-phenylphenolate aluminum (BAlq). The device structures were ITO/NPB/emitting layers/BAlq/Liq/Al in which the emitting layers were MADN: ABCV-P (40%) (device A), MADN: ABCV-P (40%): NPB (10%) (device B), MADN: ABCV-P (40%): BAlq (10%) (device C) and MADN: ABCV-P (40%): NPB (10%): BAlq (10%) (device D), respectively. The device D co-doped with NPB and BAlq exhibited maximum luminance of 9784 cd/m(2), maximum luminous efficiency of 2.82 cd/A and maximum quantum efficiency of 3.19%, respectively, whereas those of the device A doped with only ABCV-P were 7563 cd/m(2), 1.98 cd/A and 1.99%.