A Bipolar Delayed Fluorescence Luminogen with Fast Reverse Intersystem Crossing and High Horizontal Dipole Orientation for High-Performance Sky-Blue and White OLEDs

摘要

The development of robust luminescent materials plays a key role for organic light-emitting diodes (OLEDs). Herein, a tailor-made sky-blue delayed fluorescence luminogen (DCPC-BP-SFAC) containing a carbonyl acceptor and spiro[acridine-9,9 ''-fluorene] and 9,9 ''-(cyclohexane-1,1-diylbis(4,1-phenylene))bis(9H-carbazole) donors is explored, which holds merits of excellent thermal stability, strong photoluminescence, balanced carrier transport, and horizontal dipole orientation. Owing to a charge-transfer dominated singlet state and a charge-transfer and local-excitation hybrid triplet state, DCPC-BP-SFAC has a small energy gap between singlet and triplet as well as a large spin-orbit coupling constant, which result in a fast reverse intersystem crossing process and thus efficient delayed fluorescence. High-performance sky-blue OLEDs with outstanding external quantum efficiencies (eta(ext)) reaching 32.6% are achieved based on DCPC-BP-SFAC, benefiting from high exciton utilization and large light out-coupling efficiency. Moreover, using DCPC-BP-SFAC as blue emitter and host material simultaneously, efficient all-fluorescence out-of-phase sensitizing white OLEDs without interlayer are fabricated, providing high eta(ext) of up to 21.6% and stable warm-white light with a high color rendering index of 84. The outstanding electroluminescence performances demonstrate the great potentials of DCPC-BP-SFAC in practical display and lighting devices.

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