The high electron affinity conjugated polymer, poly(2,5-pyridinediyl) (PPy), can be used as the electron-transport/hole blocking layer in a light-emitting diode with poly(phenylene vinylene) (PPV) as the emitting layer, ITO as the anode and aluminum as the cathode. The incorporation of PPy layer provides an improvement in the conversion efficiency of current density to brightness by a factor of 17.