A\nTailored TADF Emitter Based on Diphenylacetylene\nAnthracene Derivatives for Highly Efficient Solution-Processed Pure\nRed Organic Light-Emitting Diodes

It\nholds enormous significance for red thermally activated delayed\nfluorescence (TADF) emitters to develop organic light-emitting diodes\n(OLEDs) with high efficiency and high color purity, which remains\nchallenging for highly efficient solution-processed red TADF emitters\ndue to the limitation of severe nonradiative decays. Herein, a red\nTADF emitter containing space interactions, 4,4′-(9,10-bis(phenylethynyl)anthracene-1,8-diyl)bis(<i>N</i>,<i>N</i>-bis(4-methoxyphenyl)aniline) (DBP-2MOTPA),\nis designed and synthesized, composed of ethynyl as the acceptor and\nmethoxytriarylamine (MOTPA) as the donor. The triphenylamine donor\nunit decorated with peripheral methoxy units not only improves the\nsolubility for the solution-processed technology but also increases\nthe electron-donating ability. The highly twisted donor−π–acceptor\n(D−π–A) architecture generates a small energy\ngap (Δ<i>E</i><sub>ST</sub>) of 0.14 eV, and the appropriate\noverlap of highest occupied molecular orbital (HOMO) and lowest unoccupied\nmolecular orbital (LUMO) leads to a supernal photoluminescence quantum\nyield (Φ<sub>PL</sub>) of 68%. Consequently, the nondoped device\nbased on DBP-2MOTPA with Commission Internationale de l’Eclairage\n(CIE) at (0.67, 0.33) exhibits the pure red emission, which satisfies\nthe Rec.1931 standard red gamut (0.67, 0.33) and approaches the Rec.2020\nstandard (0.71, 0.29). Moreover, the doped devices employing DBP-2MOTPA\nas the emitter exhibit a maximum external quantum efficiency (EQE)\nof 6.09%, which is among the effective values in the solution-processed\nred TADF-OLEDs.