Simultaneous Multi‐Resonant Thermally Activated Delayed Fluorescence and Room Temperature Phosphorescence from Biluminescent Nitrogen‐Containing Indolocarbazoles

in the near-UV (≈375 nm) and green (≈500 nm), respectively, and remarkably long phosphorescence lifetimes extending into the multi-second regime. This RTP is shown to persist even at doping concentrations as low as 0.1 wt.%. Additionally, two of the emitters exhibit multi-resonant thermally activated delayed fluorescence (MR-TADF)/RTP biluminescence, which, to the best of knowledge, would be the first examples of such behavior. Finally, insight is provided into the dependence of these competing emission pathways on the temperature and concentration, with supporting wavefunction-based computations.