Orange phosphorescent organic light-emitting diodes using new spiro[benzoanthracene-fluorene]-type host materials

New spirobenzoanthrcene-type orange phosphorescent host materials, 9-(spiro[benzoanthracene-7,9′-fluorene]-2′-yl)-9H-carbazole and 9-(spiro[benzoanthracene-7,9′-fluorene]-3-yl)-9H-carbazole, with stable efficiency roll-off, were prepared by an Ullmann coupling reaction of 2′-bromo-spiro[benzoanthracene-7,9′-fluorene] and 3-bromo-spiro[benzoanthracene-7,9′-fluorene] respectively, with carbazole. Orange phosphorescent organic light-emitting diodes with the configuration of indium tin oxide/N,N’-diphenyl-N,N’-bis-[4-(phenyl-m-tolylamino)-phenyl]-biphenyl-4,4′-diamine/N,N’-di(1-naphthyl)-N,N’-diphenylbenzidine/Host:Ir(pq)2acac/2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline/tris(8-hydroxyquinoline)aluminum/LiF/Al were developed using spiro[benzoanthracene-fluorene]-type carbazole derivatives as a host material and Ir(pq)2acac as a dopant. A device obtained from 9-(spiro[benzoanthracene-7,9′-fluorene]-2′-yl)-9H-carbazole doped with 3% Ir(pq)2acac showed an orange color purity of (0.599, 0.373) and an efficiency of 14.74 cd/A at 6.0 V. The overall result is a device with an external quantum efficiency (EQE) >8.93% at high brightness but an operating voltage of <6.0 V.

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► New benzoanthracene-7,9′-fluorene-type host materials were prepared.
► Thermally stable and high glass transition temperature up to 125 °C.
► Orange phosphorescence OLEDs with a stable efficiency roll-off were developed.
► An efficiency (14.74 cd/A at 6.0 V) and an external quantum efficiency>8.93%.