Orange phosphorescent organic light-emitting diodes based on spirobenzofluorene type carbazole derivatives as a host material

Spiro-type orange phosphorescent host materials, 9-carbazole-spiro[benzo[c]fluorene-7,9′-fluorene] (OPH-1C) and 5-carbazole-spiro[benzo[c]fluorene-7,9′-fluorene] (OPH-2C) were designed and successfully prepared by the amination reaction. The EL characteristics of OPH-1C and OPH-2C as orange host materials doped with iridium(III) bis(2-phenylquinoline)acetylacetonate (Ir(pq)2acac) were evaluated. The electroluminescence spectra of the indium tin oxide (ITO, 150 nm)/N,N′-diphenyl-N,N′-bis-[4-(phenyl-m-tolyl-amino)-phenyl]-biphenyl-4,4′-diamine (DNTPD, 60 nm)/N,N′-di(1-naphthyl)-N,N′-diphenylbenzidine (NPB, 30 nm)/9-carbazole-spiro[benzo[c]fluorene-7,9′-fluorene] (OPH-1C): Ir(pq)2acac (30 nm, 3%)/2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline(BCP, 5 nm)/tris(8-hydroxyquinoline)aluminum (Alq3, 20 nm)/LiF (1 nm)/Al (200 nm) devices show a narrow emission band with a full width at half maximum of 73 nm and a λmax = 596 nm. The device obtained from OPH-1C doped with 3% Ir(pq)2acac showed an orange color purity of (0.595, 0.387) and efficiency of 17.6 cd/A at 6.0 V.