Stable and efficient blue fluorescent organic light-emitting diode by blade coating with or without electron-transport layer

• Published in: Organic electronics Vol. 51; pp. 6 - 15
• Main Authors: Yang, Lan-Sheng, Meng, Hsin-Fei, Chang, Yu-Fan, Lien, Cheng-Hsin, Zan, Hsiao-Wen, Horng, Sheng-Fu, Duan, Lian, Qiu, Yong, Luo, C.W.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.12.2017
• Subjects: Blade coating; Double emitting layers; Lifetime; Mixed host; Organic light-emitting diode; Solution-processed; Double emitting layers; Organic light-emitting diode; Lifetime; Blade coating; Mixed host; Solution-processed
• ISSN: 1566-1199; 1878-5530
• DOI: 10.1016/j.orgel.2017.06.038

Multi-layer small-molecule blue fluorescent organic light-emitting diode (OLED) is fabricated by blade coating. The emission layer is based on a mixed host of 1-(7-(9,9′-bianthracen-10-yl)-9,9-dioctyl-9H-fluoren-2-yl)pyrene (PT-404) and electron-transport material 2,7-Bis(diphenylphosphoryl)-9,9′ -spirobifluorene (SPPO13), and the blue guest emitter is 4-4′-(1E,1′E)-2,2′-(naphthalene-2,6-diyl)bis(ethane-2,1-diyl)bis(N,N-bis(4-hexyl- Phenyl) aniline) (Blue D). A hole-transport layer of Poly-(9, 9-dioctylfluorenyl-2, 7-diyl)-co-(4, 4-(N-(4-sec-butylphenyl)) diphenylamine) (TFB) is added on top of PEDOT: PSS anode. The electrons are blocked away from TFB by a layer of pure host emission layer of PT-404 between TFB and the mixed –host emission layer. For the device with the electron transport layer of Tris(8-hydroxyquinolinato)aluminum (Alq3) blade-coated over the emission layer the efficiency and lifetime at initial brightness of 500 cd m−2 are 7.5 cd A−1 and 150 h for Alq3/CsF/Al cathode. When the Alq3/CsF/Al is replaced by simply CsF/Al over the mixed-host emission layer the efficiency and lifetime are 6.4 cd A−1 and 300 h (2 times longer than that of the Alq3/CsF/Al cathode). The lifetime depends on the electron-hole balance tuned by the mixed-host blending ratio as well as the electron injection from the cathode. This work shows good stability is possible for all-solution-processed blue OLED. [Display omitted] •The relatively high lifetime is related to the intrinsic stability of the solution-processed mixed-host of PT-404 and SPPO13 as well as the fine tuning of the electron-hole balance.•We have successfully fabricated blue fluorescent OLED devices with high efficiency and high lifetime by blade coating.