Ru Dipyrrinates as NCS-Free Sensitizers in the Dye-Sensitized Solar Cell

• Other Authors: Li, Guocan (authoraut)
• Format: Others
• Language: English; English
• Published: Florida State University
• Subjects: Chemistry; Biochemistry
• Online Access: http://purl.flvc.org/fsu/fd/FSU_migr_etd-8708

Ru-dipyrrinate polypyridyl complexes, in which dipyrrinate is directly coordinated to the Ru metal center, offer a promising platform for designing stable and efficient Ru sensitizers for dye-sensitized solar cells (DSSCs). The substitution of chelating dipyrrinate for labile NCS-ligands typically present in such sensitizers improves the stability of the complex, while a combination of strong and complementary absorption bands caused by metal-to-ligand charge transfer and dipyrrin π-π* transitions leads to remarkable panchromatic light-harvesting by these complexes. Despite such promising features, Ru dipyrrinates have remained largely unexplored. This thesis is dedicated to the study of Ru dipyrrinates as DSSC photosensitizers. The preparation and extensive characterization of a series of Ru dipyrrinate, including bis-heteroleptic, tris-heteroleptic, and terpyridine-based complexes are presented. These complexes exhibit strong optical absorptivity but are largely non-emissive. The study of electrochemical properties suggested that the lowest excited states of bis-heteroleptic Ru-dipyrrinates may not be properly positioned in energy for electron injection into the TiO2 semiconductor. This hypothesis was confirmed by injection yield study on TiO2 film using transient absorption spectroscopy, as well as by DSSC performance measurements. The tris-heteroleptic Ru-dipyrrinates have been used successfully to adjust the energy of the lowest excited state, as demonstrated by both the electrochemical and injection yield studies, thus giving rise to significantly improved DSSC efficiencies. The terpyridine-based Ru-dipyrrinates enable photo-sensitization up to 950 nm, a feature extensively desired to make panchromatic photosensitizers capable of collecting long-wavelength photons and improving the power-conversion efficiency of DSSC. === A Dissertation submitted to the Department of Chemistry and Biochemistry in partial fulfillment of the requirements for the degree of Doctor of Philosophy. === Fall Semester, 2013. === October 31, 2013. === Dipyrrin, Dye-Sensitized Solar Cell, NCS-Free, Ruthenium, Tris-Heteroleptic, TTF === Includes bibliographical references. === Michael Shatruk, Professor Directing Dissertation; James Brooks, University Representative; Geoffrey Strouse, Committee Member; Igor Alabugin, Committee Member.