Nano-morphology characterization of organic bulk heterojunctions based on mono and bis-adduct fullerenes

We have studied organic bulk heterojunction photovoltaic devices based on a bridged-bithiophene donor-acceptor type low-band gap polymer blended with PCBM and bis-PCBM. The impact of the molecular arrangement is discussed in terms of the correlation between the solar-cell performance and the degree of crystallization. Differential scanning calorimetry (DSC) and grazing-incidence X-ray diffraction (GIXRD) prove that films with bis-PCBM typically result in more amorphous blends than comparable films with PCBM. Electron tomography (ET) is used to visualize the three dimensional morphology of photoactive layers, confirming the presence of nanofibers, formed in different scales through the thickness in the blended films with mono and bis-fullerenes. (C) 2012 Elsevier B.V. All rights reserved