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

TitleElectronic structure of Fe- vs. Ru-based dye molecules
Publication TypeJournal Article
Year of Publication2013
AuthorsJohnson, PS, Cook, PL, Zegkinoglou, I, Garcia-Lastra, JM, Rubio, A, Ruther, RE, Hamers, RJ, Himpsel, FJ
JournalJournal of Chemical Physics
Start Page044709
Date PublishedJan/2013
ISBN Number0021-9606

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-pi* 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-pi* 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. (C) 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4788617]

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