Synergetic Carbonyl and Heptagonal Structure for Single‐Molecule White Organic Light‐Emitting Diodes with Dual Thermally Activated Delayed Fluorescence

Abstract Recently, an ever‐growing interest has been paid on organic single‐molecule white light‐emitting materials for effective white organic light‐emitting diodes (WOLEDs). However, subject to Kasha's rule, photons can only be emitted from the lowest excited state and thus panchromatic or dual emissions are extremely forbidden, which results in a certain challenge in achieving white emission. Herein, a strategy of synergetic carbonyl and heptagonal structure is proposed for organic single‐molecule white light emission and demonstrated by TAO/TABO/TA2O organic luminescent materials that are modified on aryl ketones/amine fragments. Among them, due to the robust intermolecular interactions triggered by synergetic carbonyl and heptagonal structure, TA2O exhibits vibrant monomer and dimer photoluminescence with dual thermally activated delayed fluorescence (TADF) characteristics. As a result, the first single‐molecule dual‐TADF WOLED based on the synergetic system is successfully fabricated with an external quantum efficiency of 7.2%. This study not only expands the scope of carbonyl and heptagonal structure for novel optoelectronic properties and applications but also opens new avenues for the development of efficient single‐molecule WOLEDs with dual TADF mechanisms.