Effect of the ionic conductivity in the systems ITO/poly(4,4′-dipentoxy-2,2′bithiophene)/aluminium and ITO/poly(3-butylthiophene)/aluminium: electrical properties in the dark and under illumination

The systems ITO/poly(4,4′-dipentoxy-2,2′bithiophene)/aluminium and ITO/poly(3-butylthiophene)/aluminium (ITO=indium—tin oxide) are characterized by the rectifying properties of the junction polymer/aluminium. The same systems also showed an open circuit voltage in the dark and, under illumination, a photocurrent decreasing in time with a diffusion trend. The last properties have been explained on the basis of water absorption by the polymers, which therefore become ionic conductors. Finally, the aluminium oxidation at the anode and the proton (or polymer) reduction at the cathode lead to the formation of a galvanic cell.