The behaviour of ITO/poly(4,4'-dipentoxy-2,2'-bithiophene) and ITO/poly(3-butylthiophene)/Al Schottky junctions has been investigated in the dark and under white light illumination, both in the air and under dry argon flux. Both systems exhibit a battery in the dark and photoelectrochemical processes under illumination, when tested in wet atmosphere. The more hydrophobic structure, the polyPT4-based one, was found to be less affected by the ionic conductivity induced by the water absorbed from the environment and the aluminium oxidation.