Cathodic photocurrents are observed when a film of the neutral form of polypyrrole-dodecylsulphate (PPy-DS), is illuminated in an electrochemical cell. This photocurrent depends on the film thickness. The variation of charge and current in the electrochemical synthesis produces films with different densities and surface morphologies, as observed by SEM. Irradiation from the electrolyte side with monochromatic light produces an action spectrum that matches the absorption spectrum of PPy-DS. Optically transparent substrate side irradiation shifts the maximal photocurrent value to longer wavelengths and promotes a general diminution of the photocurrent values. These results are in agreement with previous results obtained in our laboratory for Poly(3-methyl-thiophene) (Micaroni and De Paoli, Sol. Energy Mater. Sol. Cells 43 (1996) 79) and are interpreted in terms of the models used for solid and nanostructured semiconductors. (C) 2000 Elsevier Science B.V. All rights reserved.6017383