Molecular Engineering Towards Efficient Aggregation‐Induced Delayed Fluorescence Luminogens as Emitters and Sensitizers for High‐Performance Organic Light‐Emitting Diodes

Abstract Exploring efficient thermally‐activated delayed fluorescence materials having maximum external quantum efficiencies ( η ext,max s) exceeding 30 % for organic light‐emitting diodes (OLEDs) still remains challenging because it generally requires efficient reverse intersystem crossing (RISC), high photoluminescence quantum yield ( Φ PL ), and large optical out‐coupling efficiency ( Φ out ) simultaneously. Herein, two green aggregation‐induced delayed fluorescence (AIDF) luminogens, named XTCz‐2 and XTCz‐3, are designed and constructed by using xanthone (XT) as electron acceptor and phenylcarbazole‐substituted carbazole as donors. XTCz‐2 and XTCz‐3 exhibit distinguished advantages of high thermal stability (439–560 °C), excellent Φ PL s (84–88 %) and fast RISC rates (1.9×10 5 –4.2×10 5 s −1 ), and prefer horizontal dipole orientation and thus have high Φ out s. Consequently, they can achieve the state‐of‐the‐art electroluminescence (EL) performances with η ext,max s of up to 35.0 %. Moreover, XTCz‐3 is selected as a sensitizer for sky‐blue multi‐resonance delayed fluorescence emitter in hyperfluorescence OLEDs, providing narrow EL spectra and excellent η ext,max s of up to 33.8 % with low efficiency roll‐offs. The splendid comprehensive performances demonstrate the significant application potential of these AIDF luminogens as both light‐emitting materials and sensitizers for OLEDs.