Spontaneous stratification in composite films consisting of conjugated polymers and neat C60 prepared by electrophoretic deposition

The morphology of composite films consisting of conjugated polymers and C60 prepared by electrophoretic deposition (EPD) has been studied. While C60 exists as nanocrystals uniformly embedded in the composite films based on poly[2-methoxy-5-(2′-ethylhexyloxy)-1,4-phenylene vinylene], a spontaneous stratification of the composite films into polymer-C60-mixture and C60-microcrystal layers is observed in the films based on a polyfluorene derivative, poly[(9,9-dioctyl-2,7-divinylenefluorenylene)-alt-{2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylene}]. The results suggest that EPD can be a useful tool for controlling the morphology of bulk heterojunction systems for organic photocells.