High‐Efficiency Deep‐Blue‐Phosphorescent Organic Light‐Emitting Diodes Using a Phosphine Oxide and a Phosphine Sulfide High‐Triplet‐Energy Host Material with Bipolar Charge‐Transport Properties

Highly efficient deep-blue-phosphorescent organic light-emitting diodes have been developed using bipolar-type high-triplet-energy host materials with a carbazole core and two phosphine oxide (PPO21) or phosphine sulfide (PPS21) units. A high quantum efficiency of 19.2% with a deep-blue color coordinate of (0.14,0.16) was achieved in the deep-blue device with PPO21 as a host material (see figure).