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A dye-sensitized heterojunction of configuration n-TiO2/PD-CuPC-MV/p-CuSCN (where PD = 3,4-pyridinedicarboxylic acid anchored to TiO2, CuPC = copper(II) phthallocyanine tetrasulfonic acid ionically linked to PD, and MV = Methyl Violet complexed to CuPC) is developed to demonstrate the applicability of molecular rectification to dye-sensitized solar cells as a strategy of suppressing recombination. Short-circuit photocurrent, open-circuit voltage, energy conversion efficiency, and incident photon to photocurrent conversion of this system are higher than that of the heterojunctions of configurations n-TiO2/PD-MV/p-CuSCN, n-TiO/CuPC-MV/p-CuSCN, and n-TiO2/MV/p-CuSCN. The impressively high rectification ratio and the mode of anchorage of CuPC toTiO2 are suggested as the cause of superior photovoltaic action of the cell TiO2/PD-CuPC-MV/p-CuSCN.

It is shown that an ionic dye Y can be electrostatically bonded to an ionic molecule X of opposite charge anchored to a TiO2 surface via suitable ligands. Dye-sensitized solid-state photovoltaic cells of the configuration n-TiO2/X-Y/p-CuSCN were constructed with X = trihydroxybenzoic acid or mercurochrome and Y = methyl violet. Cells of this configuration were found to be more efficient and delivered higher short-circuit photocurrents and open-circuit photovoltages compared to the cells based only on methyl violet or mercurochrome. It is suggested that this technique would be a means of extending the spectral response of dye-sensitized photovoltaic devices. The formation of a wider barrier by coupling of anionic and cationic species also improves the cell performance by suppression of recombination.