Deep-blue thermally activated delayed fluorescence dendrimers with reduced singlet-triplet energy gap for low roll-off non-doped solution-processed organic light-emitting diodes

Abstract

Two TADF dendrimers composed of diphenylsulfone core and oligo-carbazole dendrons were developed. Compared with the reported small molecular TADF emitter bis[4-(3,6-di-tert-butylcarbazole)phenyl]sulfone (G1), dendrimers G2 and G3 inherited the blue light emission but exhibited a reduced singlet-triplet energy gap (ΔEST) with increasing the dendron generation. The efficient triplet-to-singlet (T1-to-S1) transition processes, excellent thermal and amorphous stabilities, good solution processability, and appropriate HOMO/LUMO energy levels enabled these dendrimers to serve as non-doped emitting layers for solution-processed OLEDs. The G2 device achieved deep-blue light with emission peak at 428 nm, a CIE coordinate at (0.15, 0.12) and relatively low efficiency roll-off at high current density.