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

: Thesen, M.W.; Höfer, B.; Debeaux, M.; Janietz, S.; Wedel, A.; Köhler, A.; Johannes, H.-H.; Krueger, H.


Journal of polymer science. A, polymer chemistry 48 (2010), No.15, pp.3417-3430
ISSN: 0360-6376
ISSN: 0887-624X
Journal Article
Fraunhofer IAP ()

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 (T-g = 246 degrees 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 (T-g = 220 degrees 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).