Naphthalene Derivatives End-Capped with 2-(Diphenylamino)-9,9-Diethylfluorenes for Blue Organic Light-Emitting Diodes

To investigate the electroluminescent (EL) properties of fluorescent materials based on fluorene-substituted naphthalene, multilayered OLEDs with the following sequence; indium- tin-oxide (ITO)/N,N'-di(1-naphthyl)-N,N'-diphenyl-(1,1'-biphenyl)-4,4'-diamine (NPB) (50 nm)/Blue emitting materials (30 nm)/4,7-diphenyl-1,10-phenanthroline (Bphen) (30 nm)/lithium quinolate (Liq) (2 nm)/Al (100 nm) were fabricated using these materials as emitters. These devices exhibited blue emissions. Particularly, a device using 7-(1-(1-(2-(diphenylamino)-9,9-diethyl-9H-fluoren-7- yl)naphthalen-4-yl)naphthalen-4-yl)-9,9-diethyl-N,N-diphenyl-9H-fluoren-2-amine as a blue emitting material exhibited blue emission with a luminous efficiency, a power efficiency, an external quantum efficiency, and CIE coordinates of 2.79 cd/A, 1.19 lm/W, 2.30% at 1,000 cd/m2, and (0.14, 0.12) at 8.0 V, respectively. This study demonstrates that 2-(Diphenylamino)-9,9-diethylfluorenes endcapped naphthalene derivatives have the excellent properties for blue emitting materials for OLEDs.