Highly Efficient Thermally Activated Delayed Fluorescence with Slow Reverse Intersystem Crossing

We report an efficient luminescent molecule exhibiting thermally activated delayed fluorescence with a long-delayed fluorescence lifetime of 0.8 ms. Although the reverse intersystem crossing rate constant is small at 2.1 × 103 s−1, the molecule shows a high photoluminescence quantum yield of 89 ± 2%, indicating the suppression of nonradiative decay from the triplet state. Fluorescence molecule exhibiting thermally activated delayed fluorescence with long-delayed lifetime and high photoluminescence quantum yield is reported.