Exploiting new feasibility of a phenylquinoline unit for establishing efficient green thermally activated delayed fluorescent emitter with short delayed fluorescent lifetime

Abstract

Realizing the confluence of high photoluminescence quantum yields (PLQYs) and short delayed fluorescent lifetimes remains a challenge for thermally activated delayed fluorescent (TADF) emitters. A green TADF emitter, 10-(2,4-diphenylquinolin-6-yl)-10 H -phenoxazine (PhQLPXZ), is exploited by directly linking an 2,4-diphenylquinoline unit with an electron-donating (D) 10 H -phenoxazine moiety. For the first time, the phenylquinoline (PhQL) unit is revealed as an electron-accepting unit for fabricating efficient TADF emitters. The dihedral angle between the donor and the acceptor is nearly 90°, which induces a totally separation of frontier orbitals. As a result, the emitter reveals a small singlet-triplet splitting energy of 0.09 eV and a short delayed fluorescence lifetime of 1.3 μs. The green organic light-emitting diodes (OLEDs) employing PhQLPXZ as the emitter exhibit a maximum external quantum efficiency of 15.7%. This study demonstrates for the first time that phenylquinoline derivatives can be employed for constructing TADF emitters for high-efficiency fluorescent OLEDs. • Phenylquinoline derivatives were employed to construct a green TADF emitter with a short delayed lifetime of 1.3 μs. • The molecule endows a vertical dihedral angle (97°) between the acceptor and the donor and high photoluminescence quantum yield over 70% in film. • The device with a doping concentration of 6% exhibited a high EQE of 15.7%, which is one of the best among the devices based on quinolone cored emitters.