The molecular design concept and mechanism leading to highly efficient thermally activated delayed fluorescence are presented.

We measured the fluorescence quantum yield (Φf) of several aromatic hydrocarbon crystals: p-terphenyl, trans-stilbene, anthracene, pyrene, and α-perylene. The Φf is reduced by chemical impurities, structural defects, and reabsorption of fluorescence. To minimize the effect of chemical impurities and structural defects, we evaluated the Φf of highly purified single crystals. We also measured the Φf of powder samples prepared by the mechanical milling of single crystals to assess the effect of reabsorption and structural defects induced by milling. We estimated the lower limit values of the Φf to be 0.80 for p-terphenyl, >0.65 for trans-stilbene, >0.64 for anthracene, 0.68 for pyrene, and 0.31 for α-perylene.

No abstract