White electrophosphorescent devices based on tricolour emissive layers

We demonstrate high efficiency, white organic light-emitting devices based on a structure using multiple emissive layers and fabricated without a hole-injecting layer. 2,5,8,11-tetra-tertbutylperylene (TBPe) was used as the blue fluorescent layer and the overall device configuration was indium tin oxide (ITO)/N,N'-bis(naphthalen-1-yl)-N,N'-bis(phenyl)-benzidine (NPB)/4,4'-N, N'-dicarbazole-biphenyl (CBP): bis[1-(phenyl)isoquinoline] iridium (III) acetylanetonate [Ir(piq)2(acac)]/CBP:fac-tris(2-phenylpyridine) iridium [Ir(ppy)3]/CBP: TBPe/2, 9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP)/(8-hydroxyquinoline) aluminium (Alq3)/LiF/Al. This structure possessed a maximum luminous efficiency of 14.2 cd A-1 at a current density of 4 mA cm-2 and a maximum brightness of 40 520 cd m-2 at 25 V. The Commission Internationale de L'Eclairage coordinates changed only from (0.27, 0.38) to (0.33, 0.38), with the brightness varying from 100 to 25 640 cd m-2, as the applied voltage was increased from 10 to 23 V