Development and characterization of porphyrin chromophores for solar energy conversion.

摘要

Increased public awareness of the Earth's depleting oil reserves and the adverse effect of greenhouse gasses are driving the development of alternative energy resources, including solar power. While the supply of energy from the Sun to the Earth is enormous, exploitation of this formidable natural resource remains a scientific challenge. Considerable efforts in fundamental research are still necessary for solar power to become a reality. The interesting optical and electronic properties and synthetic versatility of porphyrin chromophores constitute a valuable tool for further understanding the processes involved in efficient light-harvesting and current generation. This thesis describes the design and characterization of several porphyrin-based systems for solar energy conversion studies.; Chapter 2 reports on the synthesis, photophysical characterization, and energy transfer (EnT) applications of a series of porphyrin dimers based on Re(l) pyridyl ligation that, despite incorporation of rhenium into the assembly, remain significantly fluorescent. In the context of solar energy conversion, the dimers allow for the systematic study of factors that modulate interpigment EnT.; Chapter 3 presents a scheme for porphyrin-based multilayer sensitization of dye-sensitized solar cells (DSSCs). Porous, chromophoric, thin films based on tetrameric porphyrin squares were fabricated via layer-by-layer zirconium phosphonate chemistry, and their photoelectrochemical responses were evaluated. The studies reveal an additional, cathodic-current generating mechanism, which represents a parasitic process in the context of DSSCs.; In Chapters 4 and 5, second generation porphyrin compounds are developed in efforts of optimizing the multilayer response. Porphyrin thin films are presented in which both excited state lifetime and mobility are enhanced. The photoelectrochemical response of the films in the context of DSSCs is evaluated.; In chapter 6 a strategy is described in which the narrow absorption spectra characteristic of porphyrins is significantly broaden and shifted, allowing for enhanced light-harvesting capabilities. Mono- and di-functional terpyridine porphyrins are presented that, when reacted with labile divalent metal ions, form complexes with significantly perturbed absorption spectra. The chemistry is adapted for the fabrication of thin films via alternate deposition of metal ion and terpyridine-porphyrin motifs.