All fused ring spiro host and dopant materials for efficient blue fluorescent organic light-emitting diodes

• New spiro[benzo[de]anthracene-7,9′-fluorene]-type two dopant materials were prepared.
• Two dopant materials are thermally stable with high Tg of <148 °C.
• Sky blue fluorescence OLEDs with a color purity of (0.144, 0.261) were developed.
• Luminescence efficiency was 8.91 cd/A at 5.0 V with an EQE of >5.60%.

Novel fused ring spiro compounds, 3,9-di(di(p-tolyl))aminospiro[benzo[de]anthracene-7,9′-fluorene] (D1) and 3,9-di(di(4-biphenyl))aminospiro[benzo[de]anthracene-7,9′-fluorene] (D2) were designed and synthesized as fluorescent blue dopant materials. These compounds are light yellowish green in color and emit a sky-blue light in their photoluminescence. They possess a decomposition temperature of over 420 °C and glass transition temperature of 148 °C and 186 °C, respectively. More fused ring compounds, 1-(2-naphthyl)-10-(2-(6-phenyl)naphthyl)spiro[benzo[ij]tetraphene-7,9′-fluorene] (H3) was used as a blue host material and the electroluminescence (EL) characteristics of such were evaluated. The EL devices made of indium tin oxide (150 nm)/N,N′diphenyl-N,N′-bis[4-(phenyl-m-tolyl-amino)phenyl]-biphenyl-4,4′-diamine (DNTPD, 60 nm)/N,N,N′,N′-tetra(1-biphenyl)-biphenyl-4,4′-diamine (TBB, 30 nm/H3 hosts: D1 or D2 dopant (30 nm, 5%)/9,10-di(naphthalene-2-yl)anthracen-2-yl-(4,1-phenylene) (1-phenyl-1H-benzo[d]imidazole) (LG201, 20 nm)/LiF (1 nm)/Al (200 nm) were fabricated and characterized. The EL spectra of the devices with films fabricated via vacuum vapor deposition using an H3 host doped with D1 and D2 are similar to the PL spectrum of the solid thin film. At a 5% concentration for D1, a blue-emitting OLED was realized with an emission peak at 472 nm, a maximum luminance efficiency of 8.91 cd/A and an external quantum efficiency of 5.16% with a current density of 11.31 mA/cm2.

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