Efficient Orange–Red Thermally Activated Delayed Fluorescence Emitters Based on Dibenzo[ a,c ]Phenazine Acceptor

Thermally activated delayed fluorescence (TADF) materials have emerged as a promising class of emitters for organic light‐emitting diodes (OLEDs), offering the potential to achieve near‐unity internal quantum efficiency without requiring expensive heavy‐metal complexes. This research focuses on the design, synthesis, and characterization of novel TADF emitters based on a dibenzo[ a , c ]phenazine acceptor. The synthesized compounds, namely, MeODPA‐DBPZ and PXZ‐DBPZ, exhibit excellent thermal stability and small singlet‐triplet energy gaps, enabling efficient reverse intersystem crossing. OLED devices based on the two emitters achieve remarkable external quantum efficiencies (EQEs) of 19.5% and 22.7% for MeODPA‐DBPZ and PXZ‐DBPZ, respectively, with emission peaks at 588 and 616 nm. The EQE values remain at 17.2% and 19.0%, respectively, at a luminance of 1000 cd/m 2 . The structural‐property relationships established in this work provide valuable guidelines for future TADF material development.