XPS studies of Ru-polypyridine complexes for solar cell applications

Abstract

A series of Ru-polypyridine dyes has been studied with electron spectroscopy using AlKα and synchrotron radiation. Both pure complexes and complexes adsorbed on nanostructured TiO2 (anatase) surfaces have been examined and special emphasis was given to the dye complex cis-bis(4,4′-dicarboxy-2,2′-bipyridine)-bis-(isothiocyanato)-ruthenium(II) [Ru(dcbpy)2(NCS)2]. The measurements provide information concerning the energy level matching between the dyes and the TiO2, which is of importance in photoinduced charge transfer reactions and in applications such as dye-sensitized solar cells. The measurements also support the general picture of bonding of carboxylated complexes to the surfaces via the carboxyl groups of a single bi-isonicotinic acid ligand, and that, for Ru(dcbpy)2(NCS)2, the NCS-ligand–TiO2 interaction is small. Corroborative support is provided via quantum chemical calculations on the ligand (bi-isonicotinic acid) adsorbed on a TiO2 anatase (101) surface.

Visible-induced photocatalytic reactivity of polymer–sensitized titania nanotube films

“…To let TiO 2 nanotubes as well as TiO 2 particles be active under visible light, various types of sensitizers including organic dyes [1,2], organometallic complexes [3], and inorganic quantum dots [4] can be attached onto the surface of TiO 2 nanotubes. Among these visible light sensitizers, Ru(bpy) 3 2+ and its derivatives, attributed to organic dyes, seem to be one of the most successful and widely used in solar cells [5,6]. However, such dye sensitizers are not sufficiently stable in the aquatic environment and need to be prepared only in the acidic pH region.…”

Protonation-Dependent Binding of Ruthenium Bipyridyl Complexes to the Anatase(101) Surface

“…In the past ten years, the interaction of these dyes with the surface of titanium dioxide has been studied experimentally and theoretically in detail. [4][5][6][7][8][9][10][11][12] Most studies suggest that two carboxylate groups of the dye bind to the surface, but due to the complexity of the system, 2 uncertainty about the coordination type of the carboxylate groups and the precise orientation of the dye at the surface remains. For example, IR-experiments aimed at determining the coordination type concluded, depending on the setup, that bidentate chelating, bidentate bridging or a monodentate coordination of the carboxylate groups is possible.…”

“…[4][5][6][7]10 Furthermore, also the question which combination of the four carboxylate groups binds to the surface is not yet answered unambiguously. 8,9 Figure 1: Schematic representations of the N3, N719 and N712 dyes.…”

Electronic structure of Fe- vs. Ru-based dye molecules

“…4 and 7-11. For three-dimensional complexes, the electronic structure [12][13][14][15][16][17] and charge transfer [18][19][20][21][22][23][24] have been investigated using many spectroscopic [25][26][27][28][29][30][31] and theoretical [32][33][34][35][36][37][38][39][40] methods.…”