The interface surfaces of a CN-substituted poly(phenylenevinylene) light-emitting diode, a morphological study

The morphology of the polymer/electrode interfaces within polymer light-emitting diodes with a poly(cyanoterephthalylidene) polymer as the active layer, poly (2,5,2′,5′-hexyloxy-8,7′-dicyano-di-para-phenylenevinylene) (CN-PPV), was studied by scanning force microscopy (SFM). The structure and roughness of (i) the substrates (indium-tin oxide (ITO)), (ii) the CN-PPV films spin-coated from different solvents and concentrations, and (iii) the top electrodes of vapour-deposited aluminium were studied. Film thicknesses were determined by ellipsometry. CN-PPV films were also studied on smooth silicon substrates, to reduce the influence of substrate roughness on film morphology, and for comparison of SFM and ellipsometry results on ITO.