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

Exploring efficient thermally‐activated delayed fluorescence materials having maximum external quantum efficiencies (ηext,maxs) exceeding 30 % for organic light‐emitting diodes (OLEDs) still remains challenging because it generally requires efficient reverse intersystem crossing (RISC), high photoluminescence quantum yield (ΦPL), and large optical out‐coupling efficiency (Φout) 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 ΦPLs (84–88 %) and fast RISC rates (1.9×105–4.2×105 s−1), and prefer horizontal dipole orientation and thus have high Φouts. Consequently, they can achieve the state‐of‐the‐art electroluminescence (EL) performances with ηext,maxs 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 ηext,maxs 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. [ABSTRACT FROM AUTHOR]