Molecular Design for High Efficiency Delayed Fluorescence and Their Application in OLEDs
We demonstrate a novel pathway to open an ultimate electroluminescence (EL) efficiency by using simple aromatic compounds displaying efficient thermally activated delayed fluorescence (TADF) having high photoluminescence (PL) efficiency. We found that a proper design of organic molecules enables the formation of a small energy gap between singlet and triplet excited states (ΔEST), resulting in the enhanced T1 to S1 reverse intersystem crossing (ISC). Such an excited state is attributable to the intramolecular charge transfer (CT) of the spatially separated donor and acceptor system. We discuss the molecular design of high efficiency TADF materials based on a quantum mechanical calculation. We also demonstrate very high efficiency EL using a new series of TADF materials.
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