Amphiphilic Ruthenium(II) Terpyridine Sensitizers with Long Alkyl Chain Substitutedβ-Diketonato Ligands: An Efficient Coadsorbent-Free Dye-Sensitized Solar Cells

摘要

Three alkyl-substitutedβ-diketonato-ruthenium(II)-polypyridyl sensitizers with different alkyl chain lengths, [Ru(tctpy)(tfpd)(NCS)] (A1), [Ru(tctpy)(tfdd)(NCS)] (A2), and [Ru(tctpy)(tfid)(NCS)] (A3), were designed and synthesized for dye-sensitized solar cells (DSCs) to investigate the effect of bulky alkyl chain substituents on the photovoltaic performances (where tctpy = 4,4′,4′′-tricarboxy-2,2′:;6′,2′′-terpyridine, tfpd =1,1,1-trifluoropentane-2,4-dione, tfdd = 1,1,1-trifluorodecane-2,4-dione, and tfid =1,1,1-trifluoroicosane-2,4-dione). These complexes exhibit a broad metal-to-ligand charge transfer absorption band over the whole visible range extending up to 950 nm. All complexes were examined in the presence and absence of the coadsorbent deoxycholic acid (DCA) in dye-bath solutions. These sensitizers, when anchored to nanocrystalline TiO2films, achieve efficient sensitization to TiO2electrodes. Under standard AM 1.5 sunlight, the complexA3containing long alkyl chain length of C16yielded a short-circuit photocurrent density of 18.0 mA/cm2, an open-circuit voltage of 0.64 V, and a fill factor of 0.66, corresponding to an overall conversion efficiency of 7.6% in the absence of DCA. The power conversion efficiency ofA1sensitized DSCs was significantly increased upon the addition of DCA as compared to that in the absence of DCA. However, the photovoltaic performance ofA3was not dependent on DCA at all, probably due to the inherent structural nature of theA3molecule.