Unconventional Three-Armed Luminogens Exhibiting Both Aggregation-Induced Emission and Thermally Activated Delayed Fluorescence Resulting in High-Performing Solution-Processed Organic Light-Emitting Diodes

In this work, three-armed luminogens <b>IAcTr-out</b> and <b>IAcTr-in</b> were synthesized and used as emitters bearing triazine and indenoacridine moieties in thermally activated delayed fluorescence organic light-emitting diodes (OLEDs). These molecules could form a uniform thin film via the solution process and also allowed the subsequent deposition of an electron transporting layer either by vacuum deposition or by an all-solution coating method. Intriguingly, the new luminogens displayed aggregation-induced emission (AIE), which is a unique photophysical phenomenon. As a nondoped emitting layer (EML), <b>IAcTr-in</b> showed external quantum efficiencies (EQEs) of 11.8% for the hybrid-solution processed OLED and 10.9% for the all-solution processed OLED with a low efficiency roll-off. This was evident by the higher photoluminescence quantum yield and higher rate constant of reverse intersystem crossing of <b>IAcTr-in</b>, as compared to <b>IAcTr-out</b>. These AIE luminogens were used as dopants and mixed with the well-known host material 1,3-bis­(<i>N</i>-carbazolyl)­benzene (mCP) to produce a high-efficiency OLED with a two-component EML. The maximum EQE of 17.5% was obtained when using EML with <b>IAcTr-out</b> doping (25 wt %) into mCP, and the OLED with EML bearing <b>IAcTr-in</b> and mCP showed a higher maximum EQE of 18.4% as in the case of the nondoped EML-based device