Deep blue fluorescent host materials based on spirobenzofluorene-fluorene dimers and their properties

•New spirobenzofluorene-type host materials were prepared.•The dimers are thermally stable with high glass transition temperatures of ∼172 °C.•Deep blue fluorescence OLEDs with a color purity of (0.146, 0.148) were developed.•Luminescence efficiency was 7.44 cd A−1 at 7.0 V with an external quantum efficiency of >5.60%.

Deep blue fluorescent host materials based on the novel spiro[benzo[c]fluorene-7,9′-fluorene] dimers, 5-[spiro[benzo[c]fluorene-7,9′-fluoren]-5-yl] spiro[benzo[c]fluorene-7,9′-fluorene], 9-[spiro[benzo[c]fluorene-7,9′-fluoren]-2′-yl] spiro[benzo[c]fluorene-7,9′-fluorene], and 1,4-bis(spiro[benzo[c]fluorene-7,9′-fluorene]-5-yl)benzene were designed and successfully prepared using the Suzuki coupling reaction. The physical properties of the sprodimers and their electroluminescent characteristics as blue host materials doped with N,N,N′,N′-tetraphenylspiro[benzo[c]fluorene-7,9′-fluorene]-5,9-diamine were investigated. The device configuration used was ITO/N,N′-diphenyl-N,N′-bis[4-(phenyl-m-tolyl-amino)phenyl]biphenyl-4,4′-diamine/N,N′-di(1-naphthyl)-N,N′-diphenylbenzidine/host:5% dopant/tris(8-hydroxyquinoline)aluminum)/LiF. The device obtained from 1,4-bis(spiro[benzo[c]fluorene-7,9′-fluorene]-5-yl)benzene doped with N,N,N′,N′-tetraphenylspiro[benzo[c]fluorene-7,9′-fluorene]-5,9-diamine showed a high color purity of (0.146 and 0.148), efficiency of 7.44 cd A−1 and an external quantum efficiency of 5.60% at 7 V.

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