P‐176: High efficiency hole transporting host materials for blue phosphorescent Organic light‐Emitting Diodes

In this work, bicarbazole‐dibenzofuran backbone structure based host materials, 9′‐(dibenzo[b,d]furan‐2‐y1)‐9‐phenyl‐9H,9′H‐3,4'‐bicarbazole (3PCz4CzFu) and 9‐(dibenzo[b,d]furan‐2‐y1)‐9′‐phenyl‐9H,9'H‐3,4'‐bicarbazole (4PCz3CzFu), were designed and synthesized. Since both materials have twisted molecular structure, they showed high triplet energy of above 2.90 eV. Also, they showed high hole current density, which enabled high external quantum efficiency of over 24.0% in the deep blue phosphorescent organic light‐emitting diodes. Compared with 3PCz4CzFu, 4PCz3CzFu showed improved external quantum efficiency, efficiency roll‐off, and lifetime because 4PCz3CzFu have better hole transporting property than 3PCz4CzFu in hole only device.