Co-sensitization with near-IR absorbing cyanine dye to improve photoelectric conversion of dye-sensitized solar cells

Two carboxylated cyanine dyes, 3-butyl-2-[3-(1-butyl-5-carboxy-1,3-dihydro-3,3-dimethyl-2H-indol-2-ylidene)-1-propen-1-yl]-1,1-dimethyl-7-[1-[2-[6-(4-morpholinyl)-1,3-dioxo-1H-benz[de]isoquinolin-2(3H)-yl]ethyl]-1H-1,2,3-triazol-4-yl]-1H-Benz[e]indolium iodide (A), 2-[5-(1-butyl-5-carboxy-1,3-dihydro-3,3-dimethyl-2H-indol-2-ylidene)-1,3-pentadienyl]-3-ethyl-1,1-dimethyl-1H-Benz[e]indolium iodide (B), have been prepared and their photophysical and electrochemical properties have been investigated. A, B and their mixtures (AB) were used as sensitizers in nanocrystalline TiO2 solar cells to improve photoelectric conversion efficiency. It was found that the solar cell sensitized with A3B1 (molar ratio: A:B = 3:1) generated a high power conversion efficiency of 3.0% under AM1.5G illumination (100 mW cm−2), indicating that co-sensitization is a promising method to improve the photoelectrical properties of dye-sensitized solar cells.