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Document Type

Dissertation - University Access Only

Award Date

2013

Degree Name

Doctor of Philosophy (PhD)

Department / School

Electrical Engineering and Computer Science

First Advisor

Hongshan He

Second Advisor

David Galipeau

Abstract

Dye-sensitized solar cells (DSCs) have been widely regarded as next-generation solar cells for providing electricity at lower cost with more versatility. An overall lightto- electricity energy conversion efficiency above 11% was achieved by using ruthenium dyes, but the limited resources and the environmental issue of ruthenium provides opportunities for other organic dyes, such as porphyrin dyes. Reports showed that the most efficient meso-porphyrin dyes lacked absorption in the green and near IR regions, and detached from the TiO2 surface reducing the long-term stability of the cells. Porphyrins with a second dye (another aromatic group or a secondary porphyrin) attached to the porphyrin ring were found to have broad absorption but failed to work as efficient sensitizers due to an energy mismatch with the conduction band of TiO2. The objective of this research was to develop meso-porphyrin dyes with strong binding capability to TiO2 and broad light absorption with suitable LUMO levels that match the conduction band of TiO2. The first task was to synthesize meso-porphyrin dyes with various benzoic acid isomers anchoring groups and investigate the effect of alignment on TiO2 photovoltaic performance. The second task was to synthesize mesoporphyrin dyes with and without mesityl groups and investigate absorption broadening and photovoltaic performance. The third task was to synthesize meso-porphyrin dye with salicylic acid as an anchoring group and investigate the photovoltaic performance and binding ability. The fourth task was to synthesize meso-porphyrin dyes with hydroxylquinonline (OHQ) as anchoring group and examining the photovoltaic performance and binding ability. The fifth task was to combine complementary dyes with meso-porphyrin to enhance the absorption spectra in the green light region. The results indicate that meso-porphyrin dyes with hydroxylquinoline anchoring groups have a stronger binding ability than benzoic acid and salicylic acid anchoring groups. Broad band absorption (onset 800 nm) was achieved in meso-porphyrin dyes with hydroxylquinoline as the anchoring group and an additional donor group attached to the opposite (to the anchoring group) meso-position of porphyrin ring with suitable LUMO levels to work as an efficient sensitizer for DSCs. Absorption in the green light region can be enhanced by 12~36% using BET as complementary dye with porphyrins. The alignment of porphyrin dyes with meta-benzoic acid anchor in thin TiO2 film is more efficient for electron injection than with a para -benzoic acid anchor, while para- benzoic acid anchors in thick TiO2 film is more efficient for electron injection than meta-benzoic acid anchor. In order to further improve the cell efficiency of porphyrin dyes with conjugated hydroxyquinoline anchor, future work should focus on optimizing TiO2 film thickness and using other Bodipy dyes as co-sensitizers.

Library of Congress Subject Headings

Dye-sensitized solar cells
Porphyrins

Description

Includes bibliographical references (pages 142-149)

Format

application/pdf

Number of Pages

167

Publisher

South Dakota State University

Rights

In Copyright - Educational Use Permitted
http://rightsstatements.org/vocab/InC-EDU/1.0/

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