Photoelectrochemical cells based on polymers and copolymers from terthiophene and nitrostyrylterthiophene

This research work was aimed at improving the photovoltaic efficiency of photoelectrochemical cells (PECs) made from terthiophene based conducting polymers. Two approaches were considered. One was to use poly((E)-3 "-(p-nitrostyryl)terthiophene) in expectation that the electron withdrawing nitro substituent would enhance charge separation. The other approach was to condition the polymers at different potentials before assembly into PECs. In this way, these polymers would have different conductivities that would be expected to have different charge transport properties. Thus, polymers and copolymer from terthiophene and nitrostyrylterthiophene have been electrochemically polymerised onto indium tin oxide (ITO) coated glass. These films were characterised by cyclic voltammetry. In addition, films were electrochemically conditioned at a series of different potentials before they were characterised by UV-VIS spectrophotometry and then fabricated into PECs using liquid electrolyte. The photovoltaic tests show that the electron withdrawing nitro group results in charge separation being the dominant factor in the photovoltaic behaviour of these polymers, as evidenced by their behaviour being independent of the conditioning potential. In contrast, the photovoltaic behaviour of polytertiophene PECs shows that the best performance was obtained from the fully reduced polymers, which behave as p-type semiconductors for exciton formation and charge separation. (C) 2001 Elsevier Science B.V. All rights reserved.