Highly efficient blue-emitting materials based on 10-naphthylanthracene derivatives for OLEDs

Abstract

A series of new blue-emitting materials: 2-(10-(naphthalen-2-yl)anthracen-9-yl)pyridine ( 1 ); 1-(10-(naphthalen-2-yl)anthracen-9-yl)isoquinoline ( 2 ); 9-(3-(10-(naphthalen-2-yl)anthracen-9-yl)phenyl)-9H-carbazole ( 3 ); 9-(4-(10-(naphthalen-2-yl)anthracen-9-yl)phenyl)-9H-carbazole ( 4 ); 9-(4-(10-(naphthalen-1-yl)anthracen-9-yl)phenyl)-9H-carbazole ( 5 ); 9-(4′-(10-(naphthalen-2-yl)anthracen-9-yl)biphenyl-4-yl)-9H-carbazole ( 6 ); and 9-(4′-(10-(naphthalen-1-yl)anthracen-9-yl)biphenyl-4-yl)-9H-carbazole ( 7 ) were designed and synthesized via the Suzuki cross-coupling reaction. To explore the electroluminescent properties of these materials, multilayer OLEDs were fabricated in the following sequence: ITO/4,4′-bis( N -(1-naphthyl)-N-phenylamino)biphenyl (NPB) (50 nm)/blue-emitting materials ( 1–7 ) (30 nm) /4,7-diphenyl-1,10-phenanthroline (Bphen) (30 nm)/lithium quinolate (Liq) (2 nm)/Al (100 nm). Among those, a device using 6 as an emitter exhibited a high external quantum efficiency of 3.83% (3.20% at 20 mA/cm 2 ) with CIE coordinates of (0.152, 0.114). In order to improve EL efficiency, 1–7 were used as blue host materials for blue dopant materials 4′-[2-(2-diphenylamino-9,9-diethyl-9H-fluoren-7-yl)vinyl]- p -terphenyl ( PFVtPh ) and 3-( N -phenylcarbazol)vinyl- p -terphenyl ( PCVtPh ). Using 1 as a host material for blue dopant material PFVtPh , the resultant device showed high EL efficiencies with 10.35 cd/A, 8.77 lm/W, and 5.70% (10.24 cd/A, 6.06 lm/W, and 5.66% at 20 mA/cm 2 ). Furthermore, using 4 as a host for the PCVtPh blue dopant, device 4c exhibited efficient deep-blue emissions with a maximum external quantum efficiency of 2.96% and CIE coordinates of (0.154, 0.087), very close to the NTSC blue standard of (0.14, 0.08).