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Highly efficient and stable blue-light-emitting copolyfluorene consisting of carbazole, oxadiazole, and charge-trapping anthracene groups

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Abstract

This article presents the synthesis and electroluminescent (EL) properties of a stable blue-light-emitting copolyfluorene (P1) consisting of carbazole, oxadiazole and charge-trapping anthracene groups by Suzuki coupling reaction. The hole-transporting carbazole and electron-transporting oxadiazole improve charges injection and transporting properties, whereas the anthracene is the ultimate emitting chromophore. The thermal, photophysical, electrochemical, and EL properties of P1 were investigated by thermogravimetric analysis, differential scanning calorimeter, optical spectroscopy, cyclic voltammetry, and EL devices fabrication and characterization. P1 demonstrated high-thermal stability with thermal decomposition and glass tranistion temperatures above 400 and 145°C, respectively. In film state, P1 showed blue emission at 451 nm attributed to anthracene chromophore. Photophysical and electrochemical investigations demonstrate that effective energy transfer from fluorene to anthracene segments and charges trapping on anthracene segments leads to efficient and stable blue emission originating from anthracence. Polymer light-emitting diodes using P1 as the emitting layer (ITO/PEDOT:PSS/P1/Ca/Al) exhibited excellent current efficiency (5.1 cd/A) with the CIE coordinate being (0.16, 0.11). The results indicate that copolyfluorene is a promising candidate for the blue-emitting layer in the fabrication of efficient PLEDs. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010

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