Influence of the nature of contacts on the dark and photovoltaic characteristics of the Schottky junction between n-doped silicon and poly(4,4′-dipentoxy-2,2′-bithiophene)

The dark and photovoltaic characteristics of the Schottky junction between n-doped silicon and a conducting polymer in its oxidised form, poly(4,4'-dipentoxy-2,2'-bithiophene), have been determined as a function of the nature of the electrical contact on the polymer side. It was found that the dark and photovoltaic performances of the device depended strongly on this contact. An aluminium contact is oxidised by the polymer and an aluminium oxide film forms between the polymer and the contact through which the forward current is controlled by charge injection. The devices assembled with indium tin oxide, platinum and gold contacts show better characteristics than the ones with aluminium contact; in the last three cases, however, a faradic charge transfer reaction on the contact, probably the oxidation of some amount of water contained in the polymer, affects the characteristics of the junction.