<title>Novel hole transporting poly(triphenyldiamine)s for application in hybrid solar cells</title>

Dye-sensitized hybrid solar cells with a nanoporous TiO<SUB>2</SUB> layer and different organic hole conducting polymers have been investigated. These hole transport materials (HTM) with low glass temperature (T<SUB>g</SUB>) are based on triphenyldiamines (TPD). To enhance the power conversion efficiency, the HTMs were doped. New low T<SUB>g</SUB> TPD-based polymers were designed and synthesized with long alkoxyl groups as sidechains or in the backbone, respectively, to investigate the influence of the soft alkoxyl chains on the penetration behavior into the nanoporous layer which has been studied by SEM. The effect of the penetration depth and wetting of the dye sensitized TiO<SUB>2</SUB> layer by HTM on the solar cell efficiencies have been investigated by I-V- characteristics and steady-state measurements. To improve the penetration, the polymers were heated above T<SUB>g</SUB>. The performance of the cell is decreasing probably due to degradation of the dye during thermal treatment. To enhance the conductivity of the hole transport materials, a Li salt has been used and this doped system was compared to a doped standard Gratzel cell with OMeTAD as HTM. Crystallization on the surface could be seen after storing the standard cell for some weeks.