Blue organic light-emitting diodes using novel spiro[fluorene-benzofluorene]-type host materials

Deep blue colored, fluorescent, spiro-type host materials, 5-[4-(1-naphthyl)phenyl]-spiro[fluorene-7,9′-benzofluorene] and 5,9-bis[4-(1-naphthyl)phenyl]-spiro[fluorene-7,9′-benzofluorene] were designed and successfully prepared by the Suzuki reaction. The electroluminescence characteristics of the two compounds as blue host materials doped with blue dopant materials, diphenyl[4-(2-[1,1;4,1]terphenyl-4-yl-vinyl)phenyl]amine and 1,6-bis[(p-trimethylsilylphenyl)amino]pyrene (SPP) were evaluated. The device used comprised ITO/N,N′-bis-[4-(di-m-tolylamino)phenyl]-N,N′-diphenylbiphenyl-4,4′-diamine)/bis[N-(1-naphthyl)-N-phenyl]benzidine/Host:5% dopant/tris(8-hydroxyquinolinato)aluminium/Al–LiF. The device obtained from 5-[4-(1-naphthyl)phenyl]-spiro[fluorene-7,9′-benzofluorene] doped with 1,6-bis[(p-trimethylsilylphenyl)amino]pyrene displayed high color purity (0.138, 0.138) and high efficiency (3.70 cd/A at 7 V).