1 The Institute of Scientific and Industrial Research (ISIR), Osaka University, 8-1 Mihogaoka, Ibaraki, Osaka 567-0047, Japan. yutakaie@sanken.osaka-u.ac.jp aso@sanken.osaka-u.ac.jp.
Electron-donor function of methanofullerenes (MFs) in bulk heterojunction systems is demonstrated by the combination of MFs with the electron-transporting π-system that has a much higher electron affinity than MFs.