The photovoltaic properties of a series of phenyl-capped oligothioplienes are presented. Photovoltaic devices were prepared as sandwich type devices, with thin films of the oligomers vacuum deposited onto indium tin oxide (ITO) coated glass, and then coated with aluminium. The photovoltaic response observed was most pronounced for oligomers containing five thiophene units, with a short circuit current of 0.5 mA/cm(2) and an open circuit voltage of 1.3 V under 100 mW/cm(2) of simulated sunlight. These results correspond to an overall power conversion efficiency of similar to0.15%, which is remarkably high for a photovoltaic cell made from a single conjugated material, and significantly greater than similarly prepared octithiophene devices. Short circuit photocurrent action spectra are also reported for these devices, and their device physics discussed, including the influence of conjugation length. (C) 2003 Elsevier B.V. All rights reserved.