Electrostatic self-assembly and characterization of poly(p-phenylene vinylene)/CdS nanocomposite films

Colloidal US stabilized with (NaPO3)(6) was prepared from Cd(NO3)(2) and Na2S. The precursor of polyp-phenylene vinylene), PPV, was synthesized through Wessling's route. PPV precursor/CdS multilayer films were fabricated via the layer-by-layer electrostatic self-assembly technique. After thermal treating the PPV precursor/CdS films, PPV/CdS nanocomposite films were formed. The colloidal US and the composite films were characterized using a UV-vis spectrophotometer and a fluorescence spectrophotometer. A photoluminescence peak of the PPV/CdS multilayer film appears at around 380 nm, suggesting that the photoluminescence of the composite films should attribute to the US nanoparticles. The electroluminescence spectra show that a strong luminescence band appears in range 350 similar to 650 nm, centering around 530 nm, suggesting that the electroluminescence of the composite films should mainly attribute to PPV. For the ITO/(PPV/CdS)(20)/Al device, the threshold voltage was about 5 V, and the luminescence intensities increased as the biased voltages increased. In the PPV/CdS nanocomposite film-based light emitting device, US plays a role mainly in electron-transporting and PPV works mainly in electroluminescence. However, at higher voltages, US nanoparticles may also emit light.