  We show a way to pattern the visible electroluminescence of
solution-processed mesoporous ZnO layers. Our approach consists in locally
changing the nanoscale morphology of the coated ZnO layers by patterning the
underlying surface with thin metallic patches. Above the metal, the ZnO film is
organized in clusters that enhance its defect-induced electroluminescence. The
resulting emission occurs over a large continuum of wavelengths in the visible
and near-infrared range. This broad emission continuum is filtered by thin film
interferences that develop within the device, making it possible to fabricate
LEDs with different colours by adjusting the thickness of their transparent
electrode. When the metallic patterns used to change the morphology of the ZnO
layer reach sub-micron dimensions, additional plasmonic effects arise,
providing extra degrees of freedom to tune the colour and polarization of the
emitted photons.
