Two thermally stable and AIE active 1,8-naphthalimide derivatives with red efficient thermally activated delayed fluorescence

Red thermally activated delayed fluorescence (TADF) emitters with aggregation-induced emission (AIE) properties have been developed, based on strong electron-with-drawing 1,8-naphthalimide (NI) acceptor (A). With strong electron-rich 10-H-phenothiazine (Pz) or 9,9-dimethyl-9,10-dihydroacridine (DMAC) groups as electron donors (D), 2,6-dimethylphenyl (DM) as a π-bridge, these highly twist D-π-A architecture NI derivatives showed typical AIE feature and excellent solid-state TADF emission with high photoluminescence quantum yield (PLQY) up to 55%. Moreover, the NI derivatives exhibited excellent thermal morphological stability in their solid amorphous states, providing a stable EML for practical applications. Finally, a high external quantum efficiency (EQE) of 7.13% from Pz-DMNI, was achieved in the red OLEDs device with electroluminescence (EL) peak of 635 nm.