Multifunctional properties of D-A luminophores based on acenaphtopyrido[2,3-b]pyrazine core: photophysics, photochemistry, and efficient solution-processed OLEDs

A new series of multifunctional compounds displaying thermally activated delayed fluorescence (TADF), room-temperature phosphorescence (RTP), aggregation-induced emission (AIE) or aggregation-induced emission enhancement (AIEE) have been developed, and their optical properties investigated. The materials are based on a twisted donor-acceptor (D-A) motif using acenaphtopyridopyrazine as the acceptor core, and various donors are used for tuning their photophysical behaviour. Time-resolved spectroscopy analysis using different matrices gives a detailed image of their photophysical properties. Solution-processed organic light-emitting diodes (OLEDs) using the new compounds as emitters gave high external quantum efficiency (EQE) of up to 15.3% in the CBP matrix. The triplet excited state of the new emitters poses an opportunity for the photochemical formation of singlet oxygen (O-1(2)) species in solution. We demonstrate that the efficiency of O-1(2) generation correlates with the Delta E-ST and triplet decay lifetime. The maximum O-1(2) quantum efficiency obtained is similar to 48% for NQPy-CBZ.