First Advisor

Carl C. Wamser

Term of Graduation

Spring 1998

Date of Publication

1998

Document Type

Thesis

Degree Name

Master of Science (M.S.) in Chemistry

Department

Chemistry

Language

English

Subjects

Solar cells, Porphyrins, Oligomers

DOI

10.15760/etd.3546

Physical Description

1 online resource (viii, 130 pages)

Abstract

Mankind's attempts to harvest the sun have resulted in photocells with about 15% overall energy conversion efficiency. The best of these cells consist of a light-sensitive dye attached to a semiconductor. Absorbed light energy is transferred to the semiconductor via the delivery of an excited electron from the dye. Dye electrons are replenished with a redox solution, coupling the dye to the counter electrode.

This research was the beginning of an exploration into some potential improvements in the cell. First of all, the redox solution is a corrosive liquid, and leaks present a problem. A porphyrin oligomer with a TCPP core and TAPP branches would provide initiation sites for the growth of a conductive polymer, making a solid state solar cell. Secondly, the use of two different types of sensitizer dyes might further expand the bandwidth of wavelengths harvested.

To this end, a porphyrin pentad was synthesized, isolated, and subjected to a variety of tests. The evidence suggests that the product is the porphyrin pentad and that the pentad is capable of unidirectional charge transfer, as predicted by redox potentials of the monomers.

The UV-Vis data were typical of most porphyrin spectra, having a Soret maximum at 421 nm and Q-bands at 516, 553, 593, and 647 nm in DMSO. The shape was similar to the corresponding 4:1 mix of the monomers, but broader and red-shifted. Fluorescence measurements in DMSO yielded emission peaks at 652 and 715 nm. Excitation maxima were at 423, 517, 551, and 592 nm. These values were slightly red-shifted from TCPP. The shape of these spectra were similar to carboxy porphyrins. A 4:1 mix of monomers yielded a TAPP profile when light corresponding to the TAPP excitation frequency was used and a TCPP profile when TCPP's excitation frequency was introduced to the cell. Fluorescent lifetime data indicated a single fluorophore whose lifetime at 9.3 ns was less than most free base porphyrins. The extremely low solubility of the pentad led to NMR and mass spectrometry data that were inconclusive, showing only that the pentad was large (at least 1498 amu) and complex.

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Persistent Identifier

https://archives.pdx.edu/ds/psu/40185

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