Journal
CHEMICAL ENGINEERING JOURNAL
Volume 405, Issue -, Pages -Publisher
ELSEVIER SCIENCE SA
DOI: 10.1016/j.cej.2020.126663
Keywords
Organic light-emitting diodes; Thermally activated delayed fluorescence; Red emitters; Electron donor; Emitting dipole orientation
Categories
Funding
- National Natural Science Foundation of China [51873158, 51573141, 91833304]
- National Key R&D Program of China [2016YFB0401002]
- Shenzhen Science and Technology Program [KQTD20170330110107046, JCYJ20190808151209557]
- Key Technological Innovation Program of Hubei Province [2018AAA013]
- Natural Science Foundation for Distinguished Young Scholars of Hubei Province [2017CFA033]
- Ministry of Science and Technology of Taiwan [MOST 107-2221-E-002-160-MY3, 108-2221-E-002-148-MY3]
- Ministry of Education (MOE)
- Ministry of Science and Technology (MOST) of Taiwan
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By designing rigid and strong electron-rich donor moieties, researchers synthesized two red emitters with high rigidity and linear D-A molecular skeleton, showing distinct TADF nature and high efficiencies. The resulting OLEDs achieved high external quantum efficiency and excellent emission characteristics in the red color gamut.
Red thermally activated delayed fluorescence (TADF) emitters underperform their blue and green counterparts, largely due to their low photoluminescence quantum efficiency and isotropic orientation. Here, we designed two rigid and strong electron-rich donor moieties, 3-methyl-13H-spiro[benzo[4,5]thieno[3,2-c]acridine-5,9 ' fluorene] (MSTA) and 3-phenyl-13H-spiro[benzo[4,5]thieno[3,2-c]acridine-5,9 '-fluorene] (PSTA), by fusing benzothiophene unit on a spiro-acridine framework. Combined with a rigid, linear, and planar acenaphtho[1,2b]quinoxaline-9,10-dicarbonitrile (ANQDC) acceptor, two red emitters, ANQDC-MSTA and ANQDC-PSTA, were synthesized and characterized. In virtue of high rigidity and linear donor-acceptor (D-A) molecular skeleton, both emitters showed distinct TADF nature, high photoluminescence quantum efficiencies and high horizontal ratios of emitting dipole orientation of approximate to 85%. Consequently, the ANQDC-PSTA-based OLEDs realized high external quantum efficiency (EQE) of 24.7% at an electroluminescence peak (ELpeak) of 622 nm, together with Commission Internationale de l'Eclairage 1931 (CIE1931) coordinates of (0.61, 0.38). Furthermore, with the modulation of the microcavity effect on the device architecture, we delivered a 19.1% EQE in a deep-red EL region, with an ELpeak of 646 nm and favorable CIE1931 coordinates of (0.64, 0.36). These efficiencies are on par with the highest EL performance for red TADF OLEDs in the similar color gamut.
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