Hole-transporting host-polymer series consisting of triphenylamine basic structures for phosphorescent polymer light-emitting diodes

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Thesen, Manuel W. ; Höfer, Bianca ; Debeaux, Marc ; Janietz, Silvia ; Wedel, Armin ; Köhler, Anna ; Johannes, Hans-Hermann ; Krüger, Hartmut:
Hole-transporting host-polymer series consisting of triphenylamine basic structures for phosphorescent polymer light-emitting diodes.
In: Journal of Polymer Science Part A: Polymer Chemistry. Bd. 48 (2010) Heft 15 . - S. 3417-3430.
ISSN 0360-6376
DOI: https://doi.org/10.1002/pola.24127

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Abstract

A series of novel styrene derived monomers with triphenylamine-based units, and their polymers have been synthesized and compared with the well-known structure of polymer of N,N′-bis(3-methylphenyl)-N,N′-diphenylbenzidine with respect to their hole-transporting behavior in phosphorescent polymer light-emitting diodes (PLEDs). A vinyltriphenylamine structure was selected as a basic unit, functionalized at the para positions with the following side groups: diphenylamine, 3-methylphenyl-aniline, 1- and 2-naphthylamine, carbazole, and phenothiazine. The polymers are used in PLEDs as host polymers for blend systems with the following device configuration: glass/indium–tin–oxide/PEDOT:PSS/polymer-blend/CsF/Ca/Ag. In addition to the hole-transporting host polymer, the polymer blend includes a phosphorescent dopant [Ir(Me-ppy)3] and an electron-transporting molecule (2-(4-biphenyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole). We demonstrate that two polymers are excellent hole-transporting matrix materials for these blend systems because of their good overall electroluminescent performances and their comparatively high glass transition temperatures. For the carbazole-substituted polymer (Tg = 246 °C), a luminous efficiency of 35 cd A−1 and a brightness of 6700 cd m−2 at 10 V is accessible. The phenothiazine-functionalized polymer (Tg = 220 °C) shows nearly the same outstanding PLED behavior. Hence, both these polymers outperform the well-known polymer of N,N′-bis(3-methylphenyl)-N,N′-diphenylbenzidine, showing only a luminous efficiency of 7.9 cd A−1 and a brightness of 2500 cd m−2 (10 V). © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3417–3430, 2010