A Titanium Oxo Cluster Model Study of Synergistic Effect of Co-coordinated Dye Ligands on Photocurrent Responses.

Abstract

The use of multiple sensitizers in dye sensitized solar cells has been attractive as a promising way to achieve highly efficient photovoltaic performance. However, except for the complementary absorption, synergistic effects among the dye components have not been well understood. Herein, using ferrocene-1-carboxylate (FcCO2) and catechol (Cat) as dye ligands, two titanium oxo clusters (TOCs), [Ti3O(OiPr)6(Cat)(FcCO2)2] (1) and [Ti7O4(OiPr)8(Cat)5(FcCO2)2] (2), were synthesized and structurally characterized. Another TOC, [Ti7O3(OiPr)12(Cat)4( o-BDC)] (3) ( o-BDC = o-benzene dicarboxylate), was also prepared as a contrast. Electronic spectra and theoretical calculations showed that charge transfer occurs from ligands FcCO2 and Cat to the TiO cluster core and the contribution of redox active FcCO2 is greater than that of Cat. Using the clusters as TiO-dye pre-anchored precursors, multi-dye sensitized TiO2 electrodes were prepared. Although the two dyes FcCO2 and Cat do not complement each other in spectra, a synergistic effect on the enhancement of photocurrent responses was found and discussed in view of the inter-dyes electron communication.