Abstract

A series of 6-substituted-3-methyl-1-phenyl-4-(4-methoxyphenyl)-1H-pyrazolo[3,4-b]quinolines, MeOPAQ-X (X = t-Bu, OMe, H, F, Cl, Br), were synthesized and assessed as potential emitters in electroluminescent (EL) devices. All derivatives emitted in the blue region with an emission λ_max ranging from 448 nm to 460 nm and a quantum yield between 0.55 and 0.20. EL devices with a configuration of ITO/NPB/CBP/TPBI:MeOPAQ-X/TPBI/Mg:Ag were fabricated, where ITO, NPB, CBP, TPBI and Mg:Ag are indium tin oxide, 4,4′-bis[N-(1-naphthyl)-N-phenylamino]biphenyl, 4,4′-dicarbazolyl-1,1′-biphenyl, 2,2′,2′′-(benzene-1,3,5-triyl)tris[1-phenyl-1H-benzimidazole] and magnesium ∶ silver alloy (∼10 ∶ 1) respectively. Light emission from the dopant was observed. An external quantum efficiency around 3% could be obtained for all substituted derivatives. In particular, brightness around 13 000 cd m⁻² was achieved for the device based on MeOPAQ-H. The performances were comparable to the best available materials in the blue organic light-emitting diodes.