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 (η_ext,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 (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_PLs (84-88 %) and fast RISC rates (1.9×10⁵-4.2×10⁵ s^-1), and prefer horizontal dipole orientation and thus have high Φ_outs. Consequently, they can achieve the state-of-the-art electroluminescence (EL) performances with η_ext,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 η_ext,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.