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Document Type

Dissertation - University Access Only

Award Date

2015

Degree Name

Doctor of Philosophy (PhD)

Department

Chemistry and Biochemistry

First Advisor

Cheng Zhang

Abstract

The research presented in this dissertation addresses two fundamental issues of organic pi-conjugated materials: photochemical stability and thermal stability. The objectives of the study on photostability are to 1) develop highly photostable fluorescent polymers through theory-guided structural modification, and 2) investigate photostability enhancement strategy in a biological chromophore. On the development of photostable synthetic polymers, a polyphenylenevinylene derivative with two cyano substitutions on every vinylene unit (DiCN-PPV) has been designed and synthesized. The new polymer shows much lowered LUMO level and exhibits a photostabilility enhancement of over two orders of magnitude over the polymer without cyano substitution. To learn photostablization mechanism from the nature, a biological chromophore was extracted from Papilio dardanous butterfly wings and its structure was determined to be a L-kynurenine colvalently linked to a dopamine derivative. Comparative study shows that dopamine has a stabilization effect on L-kynurenine and is much more effective than physical blending. The second part of the research aims at developing a strategy to enhance the generally poor thermal stability of small molecule solar cells by an unconventional structural design of the light-absorbing molecular donor material. A novel ring structure is implemented in the molecule to lower the tendency of crystallization which is the main reason for the poor morphological stability. The new molecule exhibits similar solar cell device performance to the conventional material, but does not show performance degradation upon thermal annealing, indicating a more stable film morphology. The device efficiency of the new material is apparently limited by the poor phase separation of the small molecule donor and C60-based acceptor. Further improvement of performance is expected if structural modification to be done on either the donor or acceptor to reduce their miscibility.

Library of Congress Subject Headings

Polymers -- Stability Photovoltaic cells Organic compounds

Description

Includes bibliographical references (pages 71-75)

Format

application/pdf

Number of Pages

87

Publisher

South Dakota State University

Rights

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

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