Synthesis of D-A polymers with a disilanobithiophene donor and a pyridine or pyrazine acceptor and their applications to dyesensitized solar cells

New donor-acceptor polymers containing disilanobithiophene (DSBT) as the donor and pyridine or pyrazine as the acceptor with or without a thiophene spacer were prepared. The polymers showed UV-vis absorption maxima at lambda(max) = 488-526 nm, which were red-shifted relative to those of model monomers dithienylpyridine and dithienylpyrazine (lambda(max) = 352-375 nm), indicating the efficient conjugation along the polymer chains. A homo polymer of DSBT was also prepared. The DSBT-containing polymers were attached to TiO2 electrodes by immersing the electrodes in the polymer solutions under irradiation (>400 nm) or in the dark. The modified electrodes were applied to dye-sensitized solar cells and a maximal power conversion efficiency of 0.89% was obtained using the TiO2 electrode thermally modified with a DSBT-pyrazine alternating polymer.