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|Title:||ALS-CXRO Seminar | Ioannis Zegkinoglou|
|When:||03/ 6/2013 3:00 PM - 4:00 PM|
|Description:||ALS-CXRO Seminar Series|
Wed, March 6, 2013
Peter Fischer/Jinghua Guo
New Materials for Solar Cells: Advances with Soft X-Ray Spectroscopy
The energy conversion efficiency in photovoltaic and photoelectrochemical devices can be improved by deliberate tailoring of the energy levels which are relevant for the charge generation and separation processes. A generic form of such a device consists of a light absorber, an electron donor and an electron acceptor. The relative energy positions of the band edges of the light absorber with respect to the valence band maximum (VBM) of the electron donor and the conduction band minimum (CBM) of the electron acceptor determine the efficiency of current production or fuel generation from solar energy. We have used element-sensitive core-level soft x-ray spectroscopy to individually probe selected constituents of the investigated materials and determine their frontier energy levels in a number of different cases. Three examples will be presented: 1) a systematic study of custom-synthesized organometallic compounds, which can be employed as sensitizers in dye-sensitized solar cells (DSSCs), with an emphasis on molecules characterized by the promising donor-π-acceptor architecture; 2) a demonstration of the potential of heavily doped p-doped diamond as a solid electron-donating material, possibly replacing corrosive liquid electrolytes in DSSCs or expensive catalysts in solar water splitting; and 3) an investigation of the role of interfacial electronic structure and orbital anisotropy in the efficiency of hematite photoanodes for artificial photosynthesis applications.