Supramolecular Interactions of Chenodeoxycholic Acid Increase the Efficiency of Dye-Sensitized Solar Cells Based on a Cobalt Electrolyte

Abstract

A combined experimental and computational study is carried out to understand the nature of the interfaces between dye-sensitized TiO 2 and cobalt-based electrolyte in the presence of a prototype co-absorbent, chenodeoxycholic acid (CDCA), employed in Dye-Sensitized Solar Cells (DSCs). It was recently reported that including CDCA both in the dye and in the electrolyte solutions substantially improved the performance of DSCs based on a Fc/Fc + electrolyte (Daeneke et al. Nat. Chem. 2011, 3,1755). Here we evaluate the individual and combined effect of CDCA as a surface co-adsorbent and as an additive in DSCs based on a Co(II)/Co(III) electrolyte, in combination with two prototypical Ru(II) dyes, N719 and Z907. For both dyes, the concomitant use of CDCA in the dye bath and in the electrolyte solution leads to a significant improvement, by ca. a factor 2, of the DSCs photovoltaic performances, allowing us to reach 5.3% efficiency with Z907. FT-IR analyses conducted on the solid and TiO 2-adsorbed CDCA highlight the presence of surface-adsorbed interacting CDCA molecules, possibly creating a bulky insulating network on the TiO 2 surface. Computational analyses have been carried out to gain insight into the nature of the supramolecular aggregates occurring for CDCA on the TiO 2 surface.

A new terpyridine cobalt complex redox shuttle for dye-sensitized solar cells

“…[19,21] A further interesting aspect concerning Co(II)/Co(III) and Fe(II)/Fe(III) redox couples, [32] lies in the observation that including the prototype chenodeoxycholic acid (CDCA) co-adsorbent both in the dye and in the electrolyte solution substantially improved the DSCs performance, both in terms of V oc and J sc . [32,46] This unprecedented observation seems to be the key to further expanding the applicability of alternative redox couples for high performance DSCs, in line with the reported use of supramolecular chemistry to control charge recombination and other reactions in DSCs, as detailed by Planells et al [47,48].…”

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

“…In a co-sensitization system, all the dyes should have a suitable molecular structure to avoid competitive adsorption and to effectively suppress the aggregation of dyes on the TiO 2 surface. Therefore, in order to determine whether the aggregation of BPPI and N719 occurs on the surface of TiO 2 electrode, a widely used anti-aggregation co-adsorbent, chenodeoxycholic acid (CDCA) [32][33][34], was also applied in N719 sensitized DSSCs with BPPI, and the results are also listed in Table 2. When CDCA was present in the co-sensitized devices of BPPI/N719, device efficiency was not further improved (h = 6.24, J sc = 12.89 mA cm À2 , V oc = 0.74 V, and FF = 0.65).…”

Efficiency of ruthenium dye sensitized solar cells enhanced by 2,6-bis[1-(phenylimino)ethyl]pyridine as a co-sensitizer containing methyl substituents on its phenyl rings

“…To investigate the anti-aggregation effect of M0, M1o, M1p and M2 mentioned above, a widely used anti-aggregation co-adsorbent, chenodeoxycholic acid (CDCA), [26][27][28] was also applied in N719 sensitized DSSCs with and without M0, M1o, M1p and M2, and the results are listed in Table 2. When CDCA was added to N719/TiO 2 , an impressively high cell performance surpassing that of N719 (5.43%) was achieved: Z, 6.03%; J sc , 13.84 mA cm À2 ; V oc , 0.71 V; FF, 0.61 (Table 2).…”