Nanoscale Electro-Optical Properties of Organic Semiconducting Thin Films: From Individual Materials to the Blend

The wavelength dependence of the nanoscale light induced processes taking place in MEH-PPV/TCBM blended thin film samples has been studied by means of Kelvin probe microscopy implemented with controlled external sample illumination. First, both materials have been characterized individually and then these results have been used to explain the behavior of the blended sample. It has been found that green light mainly induces reversible photophysical processes with an effective photocharge generation and charge redistribution. On the contrary, under blue illumination, samples suffer a strong degradation that dominated the overall photoresponse.