The alpha-type isomer of [6,6]-phenyl-C-71-butyric acid methyl ester (alpha-[70]PCBM) has been separated into enantiomers. The structures of (R)-and (S)-alpha-[70]PCBM were unambiguously identified by X-ray crystallography. Systematic investigations on photovoltaic properties of devices based on the optically active/inactive alpha-[70]PCBM acceptor and a conjugated polymer donor revealed that the enantiomer separations and combinations have insignificant effects on the device performances.