Bisanthracene-Based Donor-Acceptor-type Light-Emitting Dopants: Highly Efficient Deep-Blue Emission in Organic Light-Emitting Devices

• Published in: Advanced functional materials 2014-04, Vol.24 (14), p.2064-2071
• Main Authors: Hu, Jian-Yong, Pu, Yong-Jin, Satoh, Fumiya, Kawata, So, Katagiri, Hiroshi, Sasabe, Hisahiro, Kido, Junji
• Format: Article
• Language: English
• Subjects: Chemical compounds; Devices; Fluorescence; Organic light emitting diodes; Photoluminescence; Polarity; Quantum efficiency; Solvents
• ISSN: 1616-301X; 1616-3028
• DOI: 10.1002/adfm.201302907

Deep‐blue fluorescent compounds are particularly important in organic light‐emitting devices (OLEDs). A donor–accepotor (DA)‐type blue‐emitting compound, 1‐(10‐(4‐methoxyphenyl)anthracen‐9‐yl)‐4‐(10‐(4‐cyanophenyl)anthracen‐9‐yl)benzene (BD3), is synthesized, and for comparison, a nonDA‐type compound, 1,4‐bis(10‐phenylanthracene‐9‐yl)benzene (BD1) and a weak DA‐type compound, 1‐(10‐phenylanthracen‐9‐yl)‐4‐(10‐(4‐cyanophenyl)anthracen‐9‐yl)‐benzene (BD2), are also synthesized. The twisted conformations of the two anthracene units in the compounds, confirmed by single crystal X‐ray analysis, effectively prevent π‐conjugation, and the compound shows deep‐blue photoluminescence (PL) with a high PL quantum efficiency, almost independent of the solvent polarity, resulting from the absence of an intramolecular charge transfer state. The DA‐type molecule BD3 in a non‐doped device exhibits a maximum external quantum efficiency (EQE) of 4.2% with a slight roll‐off, indicating good charge balance due to the DA‐type molecular design. In the doped device with 4,4′‐bis(N‐carbazolyl)‐1,1′‐biphenyl (CBP) host, the BD3 exhibits higher EQE than 10% with Commission International de L'Eclairge (CIE) coordinates of (0.15, 0.06) and a narrow full‐width at half‐maximum of 45 nm, which is close to the CIE of the high definition television standard blue. Donor–accepotor (DA)‐type deep‐blue fluorescent compounds are synthesized. Twisted conformations of the two anthracene units in the compounds effectively prevent π‐conjugation. The compounds show deep‐blue photoluminescence (PL) with a high quantum efficiency, almost independent of solvent polarity. The weak DA‐type compound exhibits an external quantum efficiency >10% and deep‐blue emission with CIE (0.15, 0.06) in a light‐emitting device.