The dispersion effect of nanoparticles on the conjugated polymer was investigated in terms of the optical and electronic properties of poly(p-phenylenevinylene) (PPV) and PPV/TiO2 nanocomposites. The photoluminescence (PL) and Fourier transform-infrared (FT-IR) spectra showed that agglomerated nanoparticles reduced the conformational disorder of the PPV segments and impeded the elimination reaction of tetrahydrothiophene. The current density and light output of the device using a particulate sol were highest at low voltage, while the current density and light output of the device using nanopowder were higher than those of the device using a particulate sol in the high field region because of the enlarged interface with an Al electrode. (C) 2003 Elsevier B.V. All rights reserved.