Synthesis and properties of polyfluorene, containing oxadiazole and carbazole units as pendants for white light-emitting diodes

Abstract

Polyfluorene-based conjugated polymer, containing oxadiazole and carbazole units as pendants, was prepared as the emitting layer in light-emitting diodes (LEDs) to show that it has higher maximum brightness and electroluminescence (EL) efficiency as compared to poly(9,9-bis(2-ethylhexyl)fluorene-2,7-diyl). The prepared polymer, poly[9-(6-(N-carbazolyl)-hexyl)-9-(6-(4-(5-phenyl-1,3,4-oxadiazolyl)-phenoxy)-hexyl)fluorene-2,7-diyl] was used as the emitting layer in LEDs. Oxadiazole and carbazole units as pendants caused aggregation to generate broad peak around 547 nm. The Commission internationale de l'eclairage coordinate of the LEDs was (0.28, 0.30) which is quite close to that of the standard white of National Television Systems Committee (0.31, 0.33). The maximum brightness and EL efficiency of the device with aluminum cathode were 6400 cd/m(2) at 10V and 0.50 cd/A at 290mA/cm(2), respectively. (c) 2008 Elsevier B.V. All rights reserved.