Synergistic Tunings on Optical and Electrical Performance of AIEgens with Hybridized Local and Charge-Transfer Excited State

The reported organic light-emitting diodes (OLEDs) based on hybridized local and charge-transfer (HLCT) state emitters mostly exhibt low photoluminescence quantum yields (PLQYs) in aggregates, failing to achieve the best device efficiency although they exhibit good exciton utilization efficiencies (EUEs). In this work, by introducing aggregation-induced emission (AIE) moiety (tetraphenylethene, TPE) and cyano group (CN) to HLCT-typed core, phenanthroimidazole (PI), six luminescent compounds with different conjugation patterns at C2 and N1 substituent positions are obtained, and their excited states are regulated effectively. Based on systematic photophysical analysis, the impacts of molecular conjugation patterns on the regulation of the locally excited (LE) and charge transfer (CT) component are disclosed, and their AIE characters that ensure high PLQYs of these compounds in aggregates are observed. Exciton conversion channels from triplets to singlets via excited states tunings are proposed based on theoretical calculations. The non-doped OLEDs based on these compounds exhibit excellent performances with maximum luminance, current efficiency, and external quantum efficiency of up to 31070 cd m‒2, 18.46 cd A‒1, and 7.16 %, respectively, and very small efficiency roll-off of 4.0 % at 1000 cd m‒2 luminance. The successful design in these HLCT-based AIEgens not only gives more optimization choices for OLED emitters, but also proves that a strategy of reasonably superposing AIE unit to HLCT emitters is feasible in materials design.