Efficient and bright non-doped blue light-emitting diodes based on glassy styrylcarbazoles

A series of styrylearbzole fluorophores 9-Ethyl-3- {(E)-2-[4-(1, 1, 1-triphenyisilyl) phenyl]-1-ethenyl}-9H-carbazole (Cz-SiPh), {4-[2-(9-Ethyl-9H-carbazol-3-yl)-vinyl]-phenyl}-naphthalen-2-yl-phenyl-amine; Cz-NPh and 3-(2-Anthracen-9-yl-vinyl)-9-ethyl-9H-carbazole (Cz-Ph3) were synthesized via Homer-Emmons-Wadsworth condensation. Fluorophores Cz-SiPh and Cz-NPh emit a blue hue, whereas Cz-Ph3 emits a green hue. Strong emission intensity, stable glassy morphology and blue emission from the solid film make fluorophores Cz-NPh and Cz-SiPh as promising blue emitters. Non-doped organic light emitting devices were fabricated using these fluorophores as an emitting layer directly; 1,3,5-tris (N-phenylbenzimidazol-2-yl)benzene and 4,4-bis(N-naphth-1-yl-N-phenylamino)-biphenyl were used as the electron-transporting layer and the hole-injection layer, respectively. Among these devices, the Cz-NPh-based device exhibits excellent performance, including high brightness (8207 cd/m(2)), large power efficiency (1.9 cd/A or 1.2 lm/W), high external quantum efficiency (2.3%), high color purity CIE (0.14, 0.09) and good operation stability. (C) 2007 Elsevier B.V. All rights reserved.