High-Power-Efficiency Blue Electrophosphorescence Enabled by the Synergistic Combination of Phosphine-Oxide-Based Host and Electron-Transporting Materials

Abstract

A new host material of (4-{1-[4-(diphenylphosphoryl)phenyl]cyclohexyl}phenyl)bis(4-methylphenyl)amine (POPCPA) is designed and synthesized by integrating electron-donating 4,4′-dimethyldiphenylamine unit and electron-accepting diphenylphosphine oxide group into the cyclohexane skeleton. The design strategy endows the host material with a high triplet energy of 2.93 eV, a shallow HOMO level of −5.24 eV, and a bipolar charge transporting feature. In addition, a new electron-transporting (ET) material of 1,3,5-tri[3-(diphenylphosphoryl)phenyl]benzene (TP3PO), which possesses a high triplet of 2.78 eV, a deep HOMO level of −6.40 eV, and a good ET ability, is constructed by the suitable combination of three diphenylphosphine oxide groups and the triphenylbenzene skeleton. These features render these phosphine-oxide-based functional materials ideal for blue phosphorescent organic light-emitting diodes (PhOLEDs). By employing these functional materials, a blue device exhibits low driving voltages of 2.6, 3.6, an...