Shedding Light on Solar Cells with Synchrotron Radiation

X-ray absorption and photoelectron spectroscopy with synchrotron radiation are used to systematically determine the energy levels of molecules for dye-sensitized solar cells (including porphyrins and phthalocyanines [1-3]). N 1s absorption spectra combined with theoretical modeling provide the unoccupied molecular orbitals and the charge transfer between the central metal atom and the surrounding N atoms. Metal 2p-to-3d spectra provide the oxidation state of the metal. Fe and Mn, which occur frequently in biological analogs, easily change their oxidation between +3 and +2. Some dyes interact with the electronic states of nano-structured ZnO acceptor electrodes, causing a change in the electronic states of the ZnO or the dye.\\[4pt] [1] P. L. Cook, et al. J. Chem. Phys. 131, 194701 (2009). \newline [2] P. L. Cook, et al. J. Chem. Phys. 131, 214702 (2009). \newline [3] J.M. Garc\'{i}a-Lastra, et al., J. Chem Phys. 133, 151103 (2010).