Hydrogen bond boosts EQEs to 30+% for acridone-carbazole based deep-blue TADF emitters in simple-structure OLEDs.

Incorporating pyridyl uniquely from its 2-position onto 10-site of acridone ring generated intramolecular hydrogen bond in a group of acridone-carbazole hybrid thermally activated delayed fluorescence emitters, which universally pulled down non-radiative transition rates by three orders and elevated reverse intersystem crossing rates by two orders, and thus boosted PLQYs to almost unity and EQEs of OLEDs to 30+%, representing the state-of-the-art efficiencies of deep-blue TICT-TADF materials and devices with CIEy≤0.10. [Display omitted] • Intramolecular-hydrogen-bond boosts performance of deep blue TADF emitters. • H-bond reduces k nr by 3 orders and increases k RISC by 2 orders. • PLQYs≈100 %, k RISC s ≥ 105 s−1 and horizontal orientation ratios ≥90 % are obtained. • Deep blue OLEDs exhibit record-high EQEs of 31–33 % with CIE y of 0.09–0.12. A group of D-A-D type thermally activated delayed fluorescence (TADF) emitters were developed with 10-(pyridin-2-yl)acridin-9(10 H)-one as acceptor and substituted carbazoles as donors. The design was focused on incorporating pyridyl to the 10-site nitrogen atom of acridin-9(10 H)-one ring, which improved the reverse intersystem crossing rate constant k RISC from 103 s−1 to 105 s−1. More importantly, the linkage of pyridyl uniquely from its 2-position to acridin-9(10 H)-one ring induced intramolecular hydrogen bond, which suppressed nonradiative transition rates by three to four orders of magnitude and universally increased the photoluminescence quantum yields from 54 % to nearly 100 %. In combination with the intrinsic high horizontal orientation ratios over 90 % of acridin-9(10 H)-one based molecules, such pyridyl decoration boosted the external quantum efficiencies of simple-structure deep blue organic light-emitting diodes to 31–33 % with CIE x of 0.15 and CIE y of 0.09 ∼ 0.12, being double of that for hydrogen-bond-free parent emitter and representing the state-of-the-art efficiencies for the deep blue twisted intramolecular charge transfer type TADF materials with CIEy ≤ 0.10 so far. These TADF emitters are comparable with the prevailing multiresonance blue emitters in terms of distinctive efficiencies, but advantageous in much facile syntheses. [ABSTRACT FROM AUTHOR]