Two of the most common moieties employed as donors and acceptors, respectively, are 9,9-dimethy-9,10-dihydroacridine (DMAC) and 2,4,6-triphenyl-1,3,5-triazine (TRZ), and the combination of the two produces the emitter DMAC-TRZ, first reported by Tsai et al. DMAC-TRZ shows a very high photoluminescence quantum yield, ΦPL, of 90%, at lPL of 495 nm, as an 8 wt% doped film in mCPCN [9-(3-(9H-carbazol-9-yl)phenyl)-9Hcarbazole-3-carbonitrile]. In DMAC-TRZ, the DEST amounts to a few tens of meV, depending on the host matrix, with a delayed fluorescence lifetime of 1.9 µs in mCBPBN, in line with an efficient RISC process. The OLED shows a high maximum external quantum yield, EQEmax, of 26.5% at lEL of 500 nm, while devices prepared from neat DMAC-TRZ films show a comparable EQEmax of 20.0%. The modest reduction of the EQEmax at high concentration can be understood in terms of the orthogonal conformation of the emitter, which effectively prevents aggregation. Both the doped and non-doped devices show a relatively small efficiency roll-off, with an EQE100 of 25.1% and 18.9%, respectively.