A Tailored TADF Emitter Based on Diphenylacetylene Anthracene Derivatives for Highly Efficient Solution-Processed Pure Red Organic Light-Emitting Diodes

It holds enormous significance for red thermally activated delayed fluorescence (TADF) emitters to develop organic light-emitting diodes (OLEDs) with high efficiency and high color purity, which remains challenging for highly efficient solution-processed red TADF emitters due to the limitation of severe nonradiative decays. Herein, a red TADF 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), is designed and synthesized, composed of ethynyl as the acceptor and methoxytriarylamine (MOTPA) as the donor. The triphenylamine donor unit decorated with peripheral methoxy units not only improves the solubility for the solution-processed technology but also increases the electron-donating ability. The highly twisted donor-π-acceptor (D-π-A) architecture generates a small energy gap (Δ<i>E</i>_ST) of 0.14 eV, and the appropriate overlap of highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) leads to a supernal photoluminescence quantum yield (Φ_PL) of 68%. Consequently, the nondoped device based on DBP-2MOTPA with Commission Internationale de l'Eclairage (CIE) at (0.67, 0.33) exhibits the pure red emission, which satisfies the Rec.1931 standard red gamut (0.67, 0.33) and approaches the Rec.2020 standard (0.71, 0.29). Moreover, the doped devices employing DBP-2MOTPA as the emitter exhibit a maximum external quantum efficiency (EQE) of 6.09%, which is among the effective values in the solution-processed red TADF-OLEDs.