New Approaches to More Effective Photosensitizers for TiO2-Based Solar Cells

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This project addresses the rational design and synthesis of new dyes for the sensitization of titanium dioxide based on the Ru(II) polypyridine motif. The properties of the dye are directly related to the properties of the ligands which surround the Ru(II) core. The absorbance of the dyes will be extended into the near IR region through the incorporation of ligands having more delocalized pi-systems and containing non-coordinated electronegative nitrogens. Based on theoretical predictions involving ligand LUMO energies, several classes of bidentate and tridentate ligands will be prepared using Friedlaender and Pfitzinger methodologies. Carboxyl groups will be introduced into the 4- and/or 4'-positions in order to anchor the dye to the semiconductor surface. Bridging ligands will be prepared to allow the formation of polynuclear systems designed to maintain strong absorbance over a wide range of the solar spectrum. Target dyes will be adsorbed on the surface of anatase and thus incorporated into a prototype solar cell. Incident photon-to-current efficiencies will be measured over the range of 350-1150 nm.Dye-sensitized solar cells (DSSCs) hold great promise as low cost, durable alternatives to existing silicon-based solar cells. The key component of a DSSC is the dye sensitizer that should absorb light strongly over the entire useful range of the solar spectrum (350-950 nm). With the support of the Organic and Macromolecular Chemistry Program, Professor Randolph P. Thummel, of the Department of Chemistry at the University of Houston, is designing and preparing new dyes expected to provide strong absorbance over a wide range of the solar spectrum. The development of more efficient photosensitizers will be useful in solar cell technology and may have further reaching significance in the way we utilize light. The efficient and economical conversion of solar to electrical energy will benefit mankind by promoting energy independence, preserving natural resources, and avoiding environmental pollution.