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

Abstract

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 (¹O₂) species in solution. We demonstrate that the efficiency of ¹O₂ generation correlates with the ΔE_ST and triplet decay lifetime. The maximum ¹O₂ quantum efficiency obtained is ∼48% for NQPy-CBZ.