Carbazole‐Based DABNA Analogues as Highly Efficient Thermally Activated Delayed Fluorescence Materials for Narrowband Organic Light‐Emitting Diodes

Abstract

Carbazole‐based DABNA analogues (CzDABNAs) were synthesized from triarylamine by regioselective one‐shot single and double borylation. The reaction proceeded selectively at the ortho position of the carbazolyl group, where the highest occupied molecular orbital is mainly localized owing to the difference in the electron‐donating abilities of the diarylamino and carbazolyl groups. The facile and scalable method enabled synthesis of CzDABNAs, exhibiting narrowband thermally activated delayed fluorescence with emission spectra ranging from deep blue to green. The organic light‐emitting diode devices employing these products as emitters exhibited deep‐blue, sky‐blue, and green emission with high external quantum efficiencies of 19.5, 21.8, and 26.7 %, respectively.

Fine-tuned asymmetric blue multiple resonance thermally activated delayed fluorescence emitters with high efficiency and narrow emission band

“…As reported, the dpa unit in the TADF emitters of this work breaks conjugation because the phenyl unit of diphenylamine is twisted by about 901, whereas the carbazole and acridine units extend the p-conjugation of the core by a fused structure, expanding the This journal is © The Royal Society of Chemistry 2022 molecular orbital distribution. 35 The twisted phenyl unit of diphenylamine may relieve intermolecular interaction compared to other planar groups of phenoxy or carbazole in the MR TADF materials. 34,36 As a result of the calculation, the HOMO levels were À4.96 eV for B-dpa-Cz, À4.76 eV for B-dpa-dmAc, and À4.79 eV for B-dpa-SpiroAc, following the relative donor strength of Cz, dmAc and SpiroAc.…”

Crystal structure, Hirshfeld surface and photophysical analysis of 2-nitro-3-phenyl-9H-carbazole

“…Carbazole-based ligands exhibit high hole-transporting mobility and strong absorption in the UV-visible spectroscopic region, and therefore show good electro-and photoactive properties (Yavuz et al, 2001). Polycyclic compounds containing two pyrrole rings have become widely used because of their good charge-transfer properties and the feasibility of tuning the electronic levels in the compound for different types of applications (Wakim et al, 2008;Reig et al, 2015;Xiang et al, 2018;Zhang et al, 2018;Szafraniec-Gorol et al, 2021), These types of compounds are therefore excellent candidates for applications such as OLEDs (organic lightemitting diodes; Svetlichnyi et al, 2010;Oda et al, 2021;Zhou et al, 2021;Bao et al, 2020), DSSCs (dye-sensitized solar cells; Zhang et al, 2009;Li et al, 2018;Lokhande et al, 2019), OPV (organic photovoltaics; Chan et al, 2013;Yang et al, 2020) and OFETs (organic field-effect transistors; Reig et al, 2015;Chen et al, 2020;Koli et al, 2020).…”

Deep‐Blue OLEDs with Rec.2020 Blue Gamut Compliance and EQE Over 22% Achieved by Conformation Engineering

“…Since then, research efforts on modification or decorating ν‐DABNA to get blueshifted emission have been continuously explored. [ 6,22–25 ] However, to the best of our knowledge, blue OLED with EQE >20% and satisfies the Rec.2020 standard (i.e., CIE y < 0.05) have not yet been reported. Moreover, it is reported that device performance of ν‐DABNA is highly sensitive to doping ratio (EQE max ranging from 13.3% to 34.4% and CIE y coordinates ranging from 0.11 to 0.23 were reported) and excimer quenching can occur even at a very low doping ratio (e.g., 1 wt%), which is ascribed to its planar π‐extended framework.…”