by Chow Lap-wai. / Thesis (M.A.)--Chinese University of Hong Kong, 1980. / Bibliography: leaves 185-188.

Tetraphenylporphyrins can be used to absorb visible light and pass on their excitation energy to electron transfer agents. The purpose of this research has been to investigate our ability to understand and control the energetics of porphyrin derivatives in order to use their electron transfer ability to harness the energy of sunlight. Shifts in the redox (reduction and oxidation) potentials of tetraphenylporphyrins result from variations in the substituents attached at the para- position of the phenyl rings of tetraphenylporphyrins, as well as variations in the state of ionization of those substituents, and the solvent in which the reactions are carried out. To measure the effect these variations, results from cyclic voltammetric experiments were plotted versus literature values of Hammett substituent constants to confirm the validity of linear free energy relationships as a model of substituent effects. Solvent effects on reduction potentials were correlated using experimentally determined values of the empirical solvent parameter ET. Some specific conclusions are summarized. 1. The usefulness of linear free energy relationships in correlating variations in redox potentials with changes in substituent was confirmed with two exceptions. Two of the porphyrins were shown to undergo a different electrochemical oxidation mechanism than the remaining porphyrins, and another porphyrin was shown to be more difficult to reduce than predicted on the basis of its substituent constant. 2. Solvent effects, here investigated as the effect of added water on the reduction potential of tetraaminophenylporphyrin in DMSO, were demonstrated to correlate with the Dimroth-Reichardt solvent parameter, ET , determined experimentally for each water-DMSO mix. 3. Variations in the state of ionization of ionizable substituents such as carboxylic acid, amine, and hydroxyl substituents were shown to affect porphyrin electrochemistry mostly through the protonation of bulk, solution-phase porphyrin by added proton donor. An additional effect of added proton donor was noted in an alteration in the mechanism of reduction to include some of a different mechanism wherein reduced porphyrin is protonated in a chemical equilibrium and then further reduced electrochemically.

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A successful model that could accurately predict the performances of n+-p-p+ concentrator solar cells should include a model of carrier photogeneration rates consistent with the spectral content of the incident light. Furthermore, a finite back surface recombination velocity should be considered since new techniques such as 'Back Surface Field' were developed to reduce the recombination rate at the rear of the cell.In the present work, a two-dimensional concentrator solar cell is modeled for low levels of injection. The model however, assumes an incident light containing one single wavelength. The incident light is assumed to decrease linearly from the center of the illuminated area until it vanishes at the edges of the cell. Finite recombination velocities are taken into account at the front and the back surfaces. Finite-width space charge regions are also included. The transport equations are solved for the carrier concentrations in different regions of the cell. The current density expressions are derived. The generation of theoretical current voltage characteristics is outlined. However, the use of these characteristics to predict cell performances is left for further research. / Department of Physics and Astronomy

Thesis (M.S.)--University of Texas at El Paso, 2007. / Title from title screen. Vita. CD-ROM. Includes bibliographical references. Also available online.

Thesis (Ph.D.)--Australian National University, 2004.

Thesis (M. App. Sc.)--Carleton University, 2003. / Includes bibliographical references (p. 112-118). Also available in electronic format on the Internet.