Multifunctional tris(triazolo)triazine-based emitter with dual-TADF, RTP, AIEE and AIDF properties

Tremendous attention in recent years has been devoted to the design of multifunctional purely organic emitters owing to their diverse emissive mechanism and widespread applications in the luminescent field. Herein, we describe the synthesis and photophysical investigation of D₃A-type tris(triazolo)triazine (TTT) multifunctional emitters with unprecedented dual thermally activated delayed fluorescence (TADF), room-temperature phosphorescence (RTP), aggregation-induced emission enhancement (AIEE), and aggregation-induced delayed fluorescence (AIDF). We demonstrate that the presence of methyl substituents at different positions of the emitter offers the possibility to switch between RTP and TADF processes by choosing appropriate hosts and controlling the singlet-triplet energy gap (ΔE_ST). TTT-PTZ, in particular, is a very strong TADF emitter (DF/PF ratio 9.3) in Zeonex®, even with a ΔE_ST around 0.20 eV, displaying high external quantum efficiency (EQE) of up to 12.4% in solution-processed organic light-emitting diodes (OLEDs).