Novel aggregation-induced delayed fluorescence luminogens for vacuum-deposited and solution-processed OLEDs with very small efficiency roll-offs

Abstract

Organic light-emitting diodes (OLEDs) fabricated with thermally activated delayed fluorescence materials usually suffer from serious efficiency roll-offs at high voltages, which restrain their practical applications. To address this issue, in this work, we design and synthesize two luminogens composed of electron-withdrawing benzoyl, electron-donating phenoxazine and 9,9-dimethyl-9,10-dihydroacridine, and dendritic tris(4-(9H-carbazol-9-yl)phenyl)amine. The thermal stabilities, energy levels, electronic structures, photophysical properties and electroluminescent performance of both luminogens are investigated and discussed. They display enhanced fluorescence with greatly increased delayed component under aggregated states, demonstrating the aggregation-induced delayed fluorescence property. Vacuum-deposited and solution-processed OLEDs were fabricated by using both luminognes as emitters, which provided high external quantum efficiencies of 16.9% and 10.7%, respectively, with the negligible efficiency roll-offs. • New luminescent molecules with aggregation-induced delayed fluorescence are developed. • Efficient vacuum-deposited and solution-processed OLEDs are fabricated. • High electroluminescence efficiencies and very small efficiency roll-offs are achieved.