Fullerene-based processable polymers as plausible acceptors in photovoltaic applications

To develop n-type processable polymeric materials for photovoltaic applications, a series of polymers was synthe- sized by grafting fullerene C60 onto polystyrene (PS). Grafted polymers were studied and compared with PS:fullerene blends. Electronical and electrical properties were first measured to define the minimal amount of C60 required for solar cells applica- tion. Then, thermal properties and rheological behavior of grafted polymers were analyzed to determine whether they could be processed from the melt. A throughout experimental study revealed that C60-grafted polymers exhibit two thresholds. The first threshold at 3-4 vol % (detected by electrical conductiv- ity, electron mobility, and melt viscosity measurements) is asso- ciated to the percolation of C60 molecules. The second threshold (evidenced by glass transition and melt viscosity measurements and confirmed by optical and atomic force micrograph observa- tions) at about 12-13 vol % is assumed to be related to the for- mation of C60 aggregates. V C 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 000: 000-000, 2012