Photocurrent of thin-film cells of regioregular polyalkylthiophene/C60 composites

We have studied steady-state photocurrents of poly(3-octylthiophene)/C60 composite thin-film cells formed with ITO/Al and ITO/Au electrodes. For the ITO/Al electrode, the photocurrent is dominated by photocarriers generated at or near the positively biased electrode, as demonstrated by clear antibatic or symbatic behaviors depending on the polarity of the bias. For the ITO/Au electrode, since the photocarrier generation near the Au electrode is not effective, the photocurrent-action spectra indicate the photo carrier generation in the bulk film. The efficiency of the bulk photogeneration enhances at the energy range of 1.4–1.9 eV, in agreement with the ESR measurements on the composite.