Affiliation:
1. State Key Laboratory of Supramolecular Structure and Materials College of Chemistry Jilin University Changchun 130012 P. R. China
2. State Key Laboratory of Integrated Optoelectronics College of Electronic Science and Engineering Jilin University Changchun 130012 P. R. China
3. Jihua Laboratory 28 Huandao Nan Road Foshan 528200 Guangdong Province P. R. China
Abstract
AbstractAdvanced multiple resonance thermally activated delayed fluorescence (MR‐TADF) emitters with high efficiency and color purity have emerged as a research focus in the development of ultra‐high‐definition displays. Herein, we disclose an approach to modulate the charge‐transfer excited states of MR emitters via intramolecular covalent bond locking. This strategy can promote the evolution of strong intramolecular charge‐transfer (ICT) states into weak ICT states, ultimately narrowing the full‐width at half‐maximum (FWHM) of emitters. To modulate the ICT intensity, two octagonal rings are introduced to yield molecule m‐DCzDAz‐BNCz. Compounds m‐CzDAz‐BNCz and m‐DCzDAz‐BNCz exhibit bright light‐green and green fluorescence in toluene, with emission maxima of 504 and 513 nm, and FWHMs of 28 and 34 nm, respectively. Sensitized organic light‐emitting diodes (OLEDs) employing emitters m‐CzDAz‐BNCz and m‐DCzDAz‐BNCz exhibit green emission with peaks of 508 and 520 nm, Commission Internationale de L'Eclairage (CIE) coordinates of (0.12, 0.65) and (0.19, 0.69), and maximum external quantum efficiencies (EQEs) of 30.2 % and 32.6 %, respectively.