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

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.