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The anchoring mechanism of N719 dye molecules on oxalic acid treated TiO 2 (OA-TiO 2) electrodes has been investigated using extended X-ray absorption fine structure (EXAFS) measurements, Fourier transform infrared spectroscopy (FTIR), UV-Vis spectroscopy and X-ray photoelectron spectroscopy (XPS). The FTIR spectroscopy of OA-TiO 2 electrodes revealed that the oxalic acid dissociates at the TiO 2 surface and binds through bidentate chelating and/or bidentate bridging. Analyses of EXAFS, FTIR, UV-Vis and XPS measurements of N719 dye loaded onto OA-TiO 2 revealed that the binding of N719 molecules takes place via interaction between Ru atom of the dye and Oof bidentate bridged oxalate ions at TiO 2 surface. This mechanism is quite different to the binding of N719 onto untreated TiO 2 (WO-TiO 2) surface, where-COOH and SCN groups of the dye directly bind to TiO 2 surface. The analyses of UV-Vis data show that the amount of N719 dye loading is much higher onto OA-TiO 2 surface as compared to the native TiO 2 surface. In addition, the incident photon to current conversion efficiency (IPCE) measurements show that presence of oxalate ions between dye and TiO 2 surface favors efficient electron transfer, and therefore, improvement in device efficiency. The dye sensitized solar cells fabricated using N719 dye sensitized onto OA-TiO 2 showed an efficiency of ~4.6%, which is significantly higher than that based on WO-TiO 2 electrode (~3.2%).

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