Synthesis, characterization, physical properties, and blue electroluminescent device applications of phenanthroimidazole derivatives containing anthracene or pyrene moiety

• Three novel blue-emissive materials based on phenanthroimidazole were developed.
• Doped and non-doped high efficiency blue EL device were fabricated.
• The structure-property relationships of the new phenanthroimidazole derivatives were studied.

By introducing a highly fluorescent anthracene, 9-(naphthalen-2-yl)anthracene or pyrene unit at the N1-phenyl of 1,2-diphenyl-1H-phenanthro[9,10-d]imidazole, three novel blue-emissive materials (ANPI, 2-NaNPI and PNPI) were synthesized and characterized, of which HOMO and LUMO orbitals are specifically segregative. Their high luminescence efficiency and excellent stability render them promising materials in electroluminescent device. The undoped three layers device using PNPI exhibits a maximum current efficiency of 4.99 cd A−1 with Commission Internationale d’Eclairage (CIEx,y) color coordinates of (x = 0.15, y = 0.17). Meanwhile, the property differences between N1-substituted and C2-substituted of diphenyl-1H-phenanthro[9,10-d]imidazole derivatives were studied. The results indicate that the change of conjugated position and moiety for those blue hosts can affect the electrical field polarization of device. Specifically, all the blue host materials containing anthracene moiety show an impressive luminous current efficiency around 12 cd A−1 when doped with sky blue fluorescent material BUBD-1.

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