5,9-Dioxa-13b-Oxophosphanaphtho[3,2,1-<i>de</i>]anthracenes Prepared by Tandem Phospha-Friedel–Crafts Reaction as Hole-/Exciton-Blocking Materials for OLEDs

We report a short synthesis of phosphorus-fused triarylphosphine oxides, 5,9-dioxa-13b-oxophosphanaphtho­[3,2,1-de]­anthracenes (DOPNAs), based on a tandem phospha-Friedel–Crafts reaction. Phosphorescence, UV–visible absorption, and photoelectron yield spectroscopy of vacuum-deposited thin films revealed that the triplet energies, optical band gaps, and ionization potentials of these materials were sufficiently large for them to be utilized in organic light-emitting diodes (OLEDs). Therefore, we fabricated a set of phosphorescent OLEDs based on the above phosphine oxides, confirming that the utilization of these compounds as hole-/exciton-blocking materials significantly improved OLED efficiencies and lifetimes.