title: Electronic structure of Fe- vs. Ru-based dye molecules.
abstract: In order to explore whether Ru can be replaced by inexpensive Fe in dye molecules for solar cells, the differences in the electronic structure of Fe- and Ru-based dyes are investigated by X-ray absorption spectroscopy and first-principles calculations. Molecules with the metal in a sixfold, octahedral N cage, such as tris(bipyridines) and tris(phenanthrolines), exhibit a systematic downward shift of the N 1s-to-π* transition when Ru is replaced by Fe. This shift is explained by an extra transfer of negative charge from the metal to the N ligands in the case of Fe, which reduces the binding energy of the N 1s core level. The C 1s-to-π* transitions show the opposite trend, with an increase in the transition energy when replacing Ru by Fe. Molecules with the metal in a fourfold, planar N cage (porphyrins) exhibit a more complex behavior due to a subtle competition between the crystal field, axial ligands, and the 2+ vs. 3+ oxidation states.
authors: Department of Physics, University of Wisconsin-Madison, 1150 University Ave., Madison, Wisconsin 53706, USA.
authors: Phillip S
authors: PS
authors: Johnson
authors: Peter L
authors: PL
authors: Cook
authors: Ioannis
authors: I
authors: Zegkinoglou
authors: J M
authors: JM
authors: García-Lastra
authors: Angel
authors: A
authors: Rubio
authors: Rose E
authors: RE
authors: Ruther
authors: Robert J
authors: RJ
authors: Hamers
authors: F J
authors: FJ
authors: Himpsel