Devices with varying concentrations of single-walled carbon nanotubes (SWNTs) dispersed in three derivatives of poly(p-phenylene vinylene) are prepared, and their electroluminescent properties evaluated. Increasing the concentration of SWNTs improves the electrical conductivity of the nanocomposites. However, an undesired increase in the electroluminescence (EL) turn-on voltage is observed for the hybrids, possibly due to photoluminescence quenching of excitons by the SWNTs. At relatively low concentrations of SWNTs, there is an increase in the EL lifetime; in contrast, at relatively high concentrations of SWNTs, due to photoluminescence quenching by the nanotubes, significant reduction in brightness and faster degradation of the EL performance of the devices is observed. (C) 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011