An archetype D-A TADF emitter is DMAC-TRZ, first reported by Tsai et al. This compound has a very small DEST of 0.046 eV in 8 wt% doped films in mCPCN resulting from the near orthogonal conformation between the dimethylacridine (DMAC) donor and the triazine (TRZ) acceptor. In this host, DMAC-TRZ has a sky-blue emission with peak photoluminescence wavelength (lPL) of 495 nm and a high photoluminescence quantum yield (FPL) of 90%. The OLEDs with this emitter showed a maximum external quantum efficiency, EQEmax, of 26.5% (at 1 cd m -2 ), at a lEL of 500 nm. DMAC-TRZ also exhibits very low concentration quenching, with the neat film of the material having a FPL of 83%; the non-doped device showed an EQEmax of 20.0%. 3 DMAC-TRZ has since been investigated extensively as the emitter in several computational and photophysical studies. Figure . Chemical structure and properties of DMAC-TRZ and several reported derivatives. The variation in reported ΔΕST values of the doped films of DMAC-TRZ originates from a combination of the different doping concentration, host, and measurement parameters used in each study.