Since the discovery of the very fast photo-induced charge transfer between conducting polymers (as donors. D) and buckminsterfullerene (C-60) (as acceptors, A), interpenetrating D/A networks have been proposed to improve the collection of free charges at the electrodes. The morphology of the D/A blend is of crucial importance and embedding the photoactive materials in a plasticing matrix was suggested as a method to overcome phase separation, and to favor homogeneity. In this contribution we report on a morphological characterization of three-component blends of the type poly (3 -octylthiophene)/ plasticizer/ C-60), with different plasticizing materials. The morphological investigation was done with transmission electron microscopy. The use of a conjugated thiophene-based plasticizer produces dispersed fullerene domains interpenetrated in the polymeric matrix.