Effect of electric field on the photoluminescence of polymer-inorganic nanoparticle composites

We report on the effect of electric field on the photoluminescence (PL) from a composite consisting of a BEHP-co-MEH-PPV conjugated polymer mixed with ZnO nanoparticles. We have found that in the absence of electric field PL emission from the BEHP-co-MEH-PPV-ZnO composite has two maxima in the blue and green-yellow regions. Application of a voltage bias to planar gold electrodes suppresses the green yellow emission and shifts the only PL emission maximum towards the blue region. Current-voltage characteristics of the BEHP-co-MEH-PPV-ZnO composite exhibit the nonlinear behaviour typical of nonhomogeneous polymer-inorganic structures. Generation of excited states in the BEHP-co-MEH-PPV-ZnO structure implies the presence of several radiative recombination mechanisms including formation of polymer-nanoparticle complexes including “exciplex” states and charge transfer between the polymer and nanoparticle that can be controlled by an electric field.