Theoretical Study on the Intermolecular Interactions of Black Dye Dimers and Black Dye–Deoxycholic Acid Complexes in Dye-Sensitized Solar Cells

Herein the intermolecular interactions in Ru­(H₃tcterpy)­(NCS)₃ (black dye) dimers, where tcterpy is 4,4′,4″-tricarboxy-2,2′:6′,2″-terpyridine, deoxycholic acid (3α,12α-dihydroxy-5β-cholan-24-oic acid, DCA) dimers, and black dye–DCA complexes in acetonitrile were investigated using density functional theory (DFT) and time-dependent DFT (TD-DFT). Among the five resulting black dye dimers, the most preferable species (<b>BB1</b>) forms intermolecular hydrogen bonds via the carboxyl groups and has a centrosymmetric structure similar to that reported for a black dye crystal. Theoretical calculations indicate six black dye–DCA complexes, and the most stable configuration (<b>BC1</b>) has three intermolecular hydrogen bonds between the two carboxyl groups of the dye ligand and one carboxyl and two hydroxyl groups of DCA. <b>BC1</b> has a higher intermolecular interaction energy than <b>BB1</b>. On the basis of these theoretical results, the structure of black dye aggregation and the aggregation suppression mechanism by DCA during the immersion process to prepare for dye-sensitized solar cell (DSSC) are discussed

Effect of Side Groups for Ruthenium Bipyridyl Dye on the Interactions with Iodine in Dye-Sensitized Solar Cells

A density functional theory (DFT) study was performed to elucidate the effect of the side group (X) in Ru(H₂dcbpy)(X₂bpy)(NCS)₂ dye on the interactions with iodide ions (I^– and I₃^–) and iodine molecule (I₂), where X is a carboxyl, nonyl, amino, or 1-pyrrolyl group, and dcbpy and X₂bpy represent 4,4′-dicarboxy-2,2′-bipyridine and 4,4′-X₂-2,2′-bipyridine, respectively. Oxidized dyes interact with I^– via the S atom of the NCS ligand perpendicular to the H₂dcbpy ligand. The relative interaction strength between the dye and I^– is amino < nonyl <1-pyrrolyl < carboxyl group. Except for dye possessing amino groups, a second I^– bonds to the first I^–, and the iodides weakly interact with the C–H bond of X₂dcbpy ligand. Additionally, I₂ interacts via the S atom of the NCS ligand perpendicular to H₂dcbpy of the neutral dye, and this interaction becomes stronger in the order of carboxyl < 1-pyrrolyl < nonyl < amino group dye. Only the neutral dye possessing amino groups interacts with I₃^– via N–H···I bonds. On the basis of theoretical results, the effect of side groups for Ru bipyridyl dye on both regeneration of oxidized dye with I^– species and recombination related to the interactions with I₂ and I₃^– species in the dye-sensitized solar cells is discussed

Cs-Modified WO₃ Photocatalyst Showing Efficient Solar Energy Conversion for O₂ Production and Fe (III) Ion Reduction under Visible Light

Cs-modification effects of WO₃ on photocatalytic O₂ evolution and Fe (III) ion reduction over WO₃ under visible light irradiation were investigated. WO₃ having cation-exchange ability at the surface was successfully prepared by hydrothermal and impregnation methods using cesium aqueous solutions. The photocatalytic activity of Cs-modified WO₃ was partially improved by the ion-exchange of Cs⁺ for H⁺ and Fe²⁺, and more than 10 times higher than that of WO₃ without any treatment. The optimized WO₃ showed 48 times higher quantum efficiency (19% at 420 nm) than that reported previously under visible light, and showed a high solar-to-chemical energy conversion efficiency (η_sun = 0.3%). This η_sun value is comparable to the solar-to-product energy conversion efficiencies of natural plant photosynthesis for biomass energy