  We report on the effect of electric field on the photoluminescence, PL, from
a composite consisting of a conjugated polymer mixed with zinc oxide
nanoparticles. We have found that in the absence of electric field PL emission
from the composite film 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 polymer-nanoparticles composite
exhibit the non-linear behavior typical of non-homogeneous polymer-inorganic
structures. Generation of excited states in the composite 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.
