Improved properties of polyfluorenevinylenes by introduction of carbazole units

Abstract

New electroluminescent polyfluorenevinylenes (PFV) copolymers with carbazole group, CzPFVs, have been synthesized by the GILCH polymerization. The carbazole groups were introduced as pendant to increase the electron rich ability of the copolymers. All CzPFVs exhibited absorption spectra with maximum peaks at around 417 nm. In the PL emission spectra of CzPFVs, maximum peaks around 463 nm and shoulder peaks around 490-500 nm were exhibited. By adjusting the feed ratios of carbazole groups in the CzPFVs, it is possible to have the higher current density and brightness, and the lower turn-on voltage due to increasing hole injection ability. The maximum luminescence of CzPFV9 was 2003 cd/m(2) at 7 V. The introduction of carbazole contents in PFVs can enhance the device performance to result in stable PL and EL spectra with high current density and brightness due to the increased hole injection ability and reduced interchain interaction between polymer backbones. Especially, the 1:1 mixture of CzPFV10 and PVK didn't show aggregation effect in PL spectra even after annealing the thin film at 80 degrees C up to 60 min, since the interchain interaction among polymer backbones with fluorenevinylene units was reduced. (c) 2008 Wiley Periodicals, Inc.