Efficient Orange–Red Thermally Activated Delayed Fluorescence Molecule Based on a Dibenzo[a,c]phenazin-11-yl(phenyl)methanone Acceptor

The development of efficient red electroluminescent materials poses a significant challenge because of the well-documented energy gap law barrier. In this study, a tailored orange–red luminogen featuring aggregation-induced emission and thermally activated delayed fluorescence behaviors, DPPM-TPA, is synthesized by linking two triphenylamine (TPA) donors to the rigid and strong electron-accepting core of dibenzo[a,c]phenazin-11-yl(phenyl)methanone (DPPM). Owing to its distinctive molecular architecture, DPPM-TPA enjoys excellent thermal stability, prefers an efficient reverse intersystem crossing process, and successfully realizes an extremely high photoluminescence quantum efficiency of 90%. The doped devices employing the DPPM-TPA emitter possess promising electroluminescent performance with maximal peaks at 562–582 nm, high maximum external quantum efficiencies (ηext,maxs) of 14.3–28.5%, and maxima luminances of 21,760–50,540 cd m–2, respectively. Moreover, the sensitized device presents even better EL performances with a peak at 570 nm and a higher ηext,max of 32.3%.