Sky‐Blue Aggregation‐Induced Delayed Fluorescence Luminogens with High Horizontal Dipole Orientation for Efficient Organic Light‐Emitting Diodes†

Comprehensive Summary Efficient and stable blue luminescent organic materials are highly demanded in the field of organic light‐emitting diodes (OLEDs) but still remain challenging. In this work, two new sky‐blue luminescent molecules comprised of electron acceptor of benzophenone and electron donors of spiro[acridine‐9,9'‐fluorene] and carbazole are designed and synthesized, and their thermal stability, electrochemical behaviors, photophysical properties, carrier transport ability and electroluminescence performance are investigated. They exhibit distinct merits of aggregation‐induced delayed fluorescence with high solid‐state photoluminescence quantum yields, balanced bipolar carrier transport and high horizontal dipole ratios. Highly efficient OLEDs using both molecules as emitters are obtained, which radiate strong sky‐blue light and provide outstanding external quantum efficiencies of up to 33.3% with small roll‐offs.