4DBFHPB is a hole transport layer material based on a hexaphenylbenzene (HPB) core with two electron-donating dibenzofuranylphenylamine peripheral groups. Dibenzofuran-terminated hole-transporters are well-known for highly efficient and long lifetime thermally activated delayed fluorescent (TADF) and phosphorescent organic light-emitting devices (OLEDs).
4DBFHPB exhibits high glass temperature (Tg) of 135 °C with superior thermal and electrical stability, and substantially improved anionic bond dissociation energy (BDE) when compared with its phenyl-containing counterpart, realizing high device stability in blue and green emitting OLEDs. Green TADF-OLED based on 4DBFHPB as HTL and 4CzIPN as the green emitter exhibited approximately 19.2% EQE and LT50 of over 24,000 h, and a low driving voltage of 4.07 eV at 1000 cd cm-2.
The material also demonstrates high triplet energy level ET of 2.7 eV, and hole transport rate of 1.5 × 10−3 cm2 V−1 s−1, 300 times greater than that of its phenyl counterpart TATT which contains two diphenylamine end groups.