Impedance spectroscopy of polymeric light emitting devices based on different poly(p-phenylene-vinylene) derivatives

Light emitting devices fabricated from different poly(p-phenylene-vinylene) (PPV) derivatives prepared by the precursor route (the unsubstituted homopolymer, a dimethoxy-substituted copolymer and an acetate-substituted copolymer) and devices based on a soluble dialkoxy-substituted homopolymer are compared with respect to their temperature-dependent impedance characteristics. Although similar activation energies of the conductivity in the range 0.4–0.5 eV are found for all polymers, the magnitude of the dielectric loss is significantly different in the polymers indicating a substantial difference in the amount of doping and/or impurities.