LAUSR

The design and synthesis of blue thermally activated delayed fluorescence (TADF) emitters that have high electroluminescence (EL) efficiency and low efficiency roll-off feature remains a great challenge. Herein, we developed a facile and efficient strategy by shielding acceptors with carbazole units for constructing high performance blue TADF emitters. Benzonitrile (BN), 9, 9-diphenylacridan (DPAc), carbazole (Cz) were adopted as acceptor, donor and protector, respectively, to build two TADF emitters named DPAc-DCzBN and DPAc-DtCzBN. The nondoped organic light-emitting diodes (OLEDs) of DPAc-DCzBN as emitter exhibited a standard sky-blue emission with CIE (Commission Internationale de L'Eclairage) coordinates of (0.16,0.26), high external quantum efficiency (EQE) of 20.0% and low efficiency roll-off (EQEs of 19.5%, 16.1% and 12.6% at 100, 500 and 1000 cd m‒2, respectively) which is an outstanding nondoped blue TADF OLEDs. The doped device of DPAc-DtCzBN displayed a pure blue emission and corresponding CIE coordinates is (0.16, 0.15). Meanwhile, it also demonstrated high and stabilized EQE value of 23.1%, 18.3% and 11.5% at maxima, 100 and 500 cd m‒2, respectively, which is a quite high level among the pure-blue TADF OLEDs. This study testifies the feasibility of our strategy in constructing high performance TADF electroluminescent materials.