Enhance the performance of dye-sensitized solar cells by co-sensitization of 2,6-bis(iminoalkyl)pyridine and N719

Three organic dyes 2,6-bis(iminoalkyl)pyridines [2,6-(2,6-R ₂C₆H₂NCMe)₂]C₅H ₃N (R = methyl, ethyl, isopropyl) (named DM, DE and DP, respectively) were synthesized and assembled onto nanocrystalline TiO₂ film to prepare 2,6-bis(iminoalkyl)pyridine/N719 co-sensitized photoelectrodes for dye-sensitized solar cell (DSSCs) applications, and their photoelectrochemical performances were studied. In each of the three composite electrodes, the aggregation of N719 was alleviated and its spectra response was enhanced by the 2,6-bis(iminoalkyl)pyridines in region of 400 to 750 nm, and the total resistance of DSSCs was decreased after co-sensitizing with 2,6-bis(iminoalkyl) pyridine, all of which facilitate to improve efficiency of DSSCs. The optimized cell which was co-sensitized with DM gave a short circuit current density of 16.57 mA cm^-2, an open circuit voltage of 0.72 V and a fill factor of 0.59 corresponding to an overall conversion efficiency of 7.00% under standard global AM1.5 solar irradiation conditions, which is 28.91% higher than that for DSSCs only sensitized by N719 (5.43%). The incident photo-to-current conversion efficiency, electrochemical impedance spectroscopy, surface photovoltage spectroscopy and UV-visible adsorption spectra were used to analyze their photoelectrochemical performances, and X-ray single-crystal structural analysis was used to analyze the structures of 2,6-bis(iminoalkyl)pyridines.