While the recent conceptual progress in MR-TADF emitter design has delivered a burgeoning number of efficient B/N-doped compounds that emit across the entirety of the visible spectrum, few tactics have been advanced to exploit the promising class of C=O/Nbased MR-TADF emitters, which are represented by the emitter DiKTa (Figure ). Recently, Yasuda et al. reported a linearly extended C=O/N-based emitter, QA-2 (Figure ) displaying TADF in 3 wt% PPCz doped film, with a ΔEST of 0.19 eV. Similar to the design strategy used for v-DABNA, where the central ring is functionalized with meta-disposed B-π-B and N-π-N groups, QA-2 also contains meta-disposed C=O-π-C=O and N-π-N, which leads to an improvement of the TADF properties over the parent compound DiKTa, with a faster delayed lifetime (48 µs in 3 wt% PPCz and 93.3 µs in 5 wt% mCP, respectively). Despite the apparent increased conjugation length, a slightly blue-shifted λPL of 465 nm in toluene was observed for QA-2, compared to that of DiKTa (DEST of 0.15 eV and λPL of 473 nm in toluene). The OLED with QA-2 showed an EQEmax 19.0%. Our group has recently reported a helically chiral isomer of QA-2 that contains meta-disposed C=O-π-C=O and N-π-N skeleton. Enantiomers of Hel-DiDiKTa (Figure ) display circularly polarized luminescence (CPL), with a |gPL| of 4 × 10 -4 , but likewise, its λPL (473 nm) is similar to that of DiKTa.