Design, Synthesis and Charaterization of Polymers Derived from Fluorene for Application in RGB Polymer Light-Emitting-Di
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Design, Synthesis and Charaterization of Polymers Derived from Fluorene for Application in RGB Polymer Light-Emitting-Diodes Serge Beaupré and Mario Leclerc Centre de Recherche en Sciences et Ingénierie des Macromolécules Université Laval, Cité Universitaire Québec, Canada, G1K 7P4 Isabelle Lévesque and Marie D'Iorio National Research Council of Canada, Institute for Microstructural Sciences Montreal Road, Ottawa, Ontario, Canada, K1A 0R6 ABSTRACT In order to obtain efficient blue, green and red light-emitters as active layers in polymer light-emitting diode (PLEDs), we report herein the design, the synthesis, and the characterization of new polyesters and copolymers derived from fluorene. We will focus on a new approach to obtain a stable, high luminance blue emitter via polyesters derived from fluorene. The versatile synthetic approach allows the easy design of a whole class of new and tunable electroactive and photoactive aromatic polyesters. Poly(1,6-hexane9,9',9',9'',9''-hexahexyl-7,2';7',2''-terfluorene-2,7''-dicarboxylate) (PTFHHC6) and Poly(1,6-hexane-2,7-Bis(1,1’-biphenylen-4-yl-4'-dicarboxylate)-9,9-dioctylfluorene) (PE-BP-DOF-BP) exhibit strong emission in the blue range, both in solution and in the solid state. Moreover, these polyesters present some advantages over other polyfluorene derivatives. For example, their solid-state fluorescence spectrum does not show the formation of any excimer and does not vary upon thermal treatment. We will also present copolymers derived from fluorene which emit green light and a new approach to obtain red polymer light-emitting-diode will also be shown. Optical properties such as light absorption, light emission and quantum yield of fluorescence in solution as well as electrical properties such as cyclic voltammogram and conductivity in-situ are reported. Finally, some of the polymers presented have been tested in PLEDs devices and the preliminary results seem promising for the development of multicoloured displays made from the same class of polyfluorene derivatives. INTRODUCTION Since the original report of light-emitting diodes using π-conjugated polymers by the Cambridge group[1], the search for new electroactive and photoactive polymers has expanded rapidly. This tremendous discovery has led to a great interest in developing efficient and stable PLEDs in order to obtain the three primary colors (red, green and blue). Many blue electroluminescent polymers have been synthesized, such as poly(pphenylene)s[2], poly(vinylcarbazole)s[3], poly(oxadiazole)s[4], and poly(2,7-(9,9dialkylfluorene))s[5-9]. Among these polymers, poly(2,7-(9,9-dialkylfluorene)) shows interesting optical and electrical properties for the development of blue light-emitting diodes. However, many studies on polyfluorene derivatives have revealed the formation of excimers which hinder their use in electroluminescent devices. We have shown that C5.34.1
segmented conjugated polyesters derived from fluorene inhibit the excimer formation[10]. We report here the optical and electrochemical properties o
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