n-Type host materials based on nitrile and triazine substituted tricyclic aromatic compounds for high-performance blue thermally activated delayed fluorescence devices

Novel n-type host materials based on tricyclic aromatic compounds, dibenzo[b,d]furan and dibenzo[b,d]thiophene (2Trz6CNDBF 2Trz6CNDBT), have been successfully synthesized characterized for high-performance blue thermally activated delayed fluorescence (TADF) organic light-emitting devices (OLEDs). Dibenzo[b,d]furan were utilized as central molecular building blocks to achieve excellent thermal stability high triplet energy (ET). Nitrile diphenyltriazine functional groups introduced at the 6- 2- positions of low-lying lowest unoccupied orbital (LUMO) levels, ET, electron transport properties. UV–Vis absorption, low-temperature photoluminescence, ultraviolet photoelectron spectroscopy analysis showed that 2Trz6CNDBF 2Trz6CNDBT possessed ET (2.95 2.88 eV) LUMO levels (−3.43 −3.16 well-matched with a TADF emitter, 5CzCN. Moreover, electron-only device (EOD) result revealed had Blue OLEDs fabricated p-type material, mCBP, host, or 2Trz6CNDBT, exhibited lower driving voltages (3.34 3.26 V, respectively) than OLED only mCBP (3.83 V). superior external quantum efficiency (ηext, 15.6 14.7%), current (ηce, 33.8 32.7 cd A−1), power (ηpe, 25.6 25.7 lm W−1), respectively. The ηext ηce increased by more 70% ηpe approximately 150% compared those single mCBP. In addition, lifetimes 1000%. efficient injection level, effective exciton confinement film morphology provided enhanced lifetime 2Trz6CNDBT.