Nondoped Organic Light-Emitting Diodes with Low Efficiency Roll-Off: Combination of Aggregation-Induced Emission, Hybridized Local and Charge-Transfer State as well as High Photoluminescence Efficiency
In this work, two isomers namely 2P-BT-N-2TPA and 2TPA-BT-N-2P have been designed and synthesized with hybridized local and charge transfer (HLCT) properties. The 2TPA-BT-N-2P has been found to have not only stronger intra/intermolecular interactions with regular molecular packing which stabilized the excited state configuration, but also aggregation-induced emission enhancement (AIEE) properties. The AIEE properties can effectively inhibit aggregation caused quenching (ACQ) effect in the aggregation state and its photoluminescence quantum yield (PLQY) up to 91%, which is extremely high in solid-state film. When 2TPA-BT-N-2P is applied as a dopant to form a doped OLED, the device has excellent external quantum efficiency (EQE) of 6.6% with an emission peak of 588 nm. Moreover, when 2TPA-BT-N-2P is applied as a pure emitting layer to form a non-doped OLED, the device still achieved EQE of 5.8% and 5.1% at 100 cd/m2 and 1000 cd/m2, respectively, with the lowest efficiency roll-off currently reported from HLCT molecule in orange emission.