This investigation reports the luminescent and electric properties of phenyl-substituted poly (para-phenylene vinylene) copolymer (HY-PPV) in which An nanoparticles were incorporated. Incorporating a few amounts of An nanoparticles into HY-PPV film enhances the electroluminescence (EL) efficiency of HY-PPV-based polymer light emitting diodes (PLEDs) using Al and Cu as cathodes. Blue-shifts in the emission spectra and a decrease in the capacitance of the emitting layer were observed. These unique behaviors are due to the increase in the density of the effective hole trap centers and affect the electronic configuration of HY-PPV, induced by the Au nanoparticles, which increase the probability of hole-electron recombination and shift the emission spectra toward higher photo energies. (c) 2006 Elsevier B.V. All rights reserved.