Abstract: A series of fluorinated phenylpyridine-based electron-transport materials (ETMs) for organic light-emitting devices (OLEDs) based on B3PyPB were developed, and the influence of fluorine atom(s) in the core skeleton on their physical properties, such as molecular orientation, electron-transport and electron- injection, was investigated. The monofluorinated ETM exhibited a relatively large orientation order parameter of –0.23 and an electron mobility of 10–3 cm2 V–1 s–1, which was 10 times higher than that of its nonfluorinated counterpart because of concerted intermolecular interactions involving not only the CH/N hydrogen bonds but also the aromatic fluorine atoms, in addition to π–π stacking. Surprisingly, the difluorinated ETM exhibited smaller molecular orientation order parameter than that of the mono- and nonfluorinated ETMs, likely because of the poor intermolecular interactions between the fluorine atoms and nitrogen lone pairs. Blue phosphorescent OLEDs fabricated using the monofluorinated ETM had a low operation voltage of 3.5 V at 1000 cd m–2.

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