Morphology and fluorescence quenching in photovoltaic samples containing fullerene and poly(p-phenylene-vinylene) derivatives

We have studied the morphology of different heterogeneous samples containing poly[2-methoxy,5-(3',7'-dimethyl-octyloxy)]-p-phenylene-vinylene (MDMO-PPV) and either fullerene (C60) or 6,6-phenyl C61-butyric acid methyl ester (PCBM) using atomic force microscopy in the shear force detection mode or pulsed-force mode and near-field scanning optical microscopy. These investigations confirm the large influence of preparation conditions on the morphology. Systematic variation of the layer thicknesses in two-layer samples indicate that fluoresecence quenching is restricted to an interface layer with a thickness of about 40 nm.