Characterization of poly(p-phenylene vinylene)/methanofullerene blends of polymer solar cells by time-of-flight secondary ion mass spectrometry

The performance of bulk heterojunction solar cells (BHSC) strongly depends on the molecular morphology of the 100 nm thick spin cast photoactive films of the polymer/fullerene composites used. Using dynamic TOF-SIMS, we show here that spontaneous stratification is absent for several methanofullerene concentrations by use of a deuterium labeled methanofullerene in composite films of a poly(p-phenylene vinylene) and a methanofullerene. In addition, imaging TOF-SIMS on annealed samples shows a dramatic increase in phase segregation on a sub-micron level. The TOF-SIMS results are supported by transmission electron microscopy (TEM) and atomic force microscopy (AFM) measurements. # 2004 Elsevier B.V. All rights reserved