Enhanced performance of ruthenium dye-sensitized solar cell by employing an organic co-adsorbent of N,N＇-bis（（pyridin-2-yl）（methyl）methylene）-o-phenylenediamine

A pyridine-anchor co-adsorbent of N,N＇-bis（（pyridin-2-yl）（methyl） methylene）-o-phenylenediamine（named BPPI） is prepared and employed as co-adsorbent in dye-sensitized solar cells（DSSCs）. The prepared co-adsorbent could overcome the deficiency of N719 absorption in the low wavelength region of visible spectrum, offset competitive visible light absorption of I_3~-, enhance the spectral responses of the co-adsorbed TiO_2 film in region from 300 nm to 750 nm, suppress charge recombination, prolong electron lifetime, and decrease the total resistance of DSSCs. The optimized cell device co-sensitized by BPPI/N719 dye gives a short circuit current density of 12.98 m A cm~（-2）, an open circuit voltage of 0.73 V,and a fill factor of 0.66 corresponding to an overall conversion efficiency of 6.22% under standard global AM 1.5 solar irradiation, which is much higher than that of device solely sensitized by N719（5.29%）under the same conditions. Mechanistic investigations are carried out by various spectral and electrochemical characterizations.