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Qianqian
Zhang
Author
Department of Chemistry
College of Arts and Sciences
DESIGN AND SYNTHESIS OF CONJUGATED POLYMERS FOR ORGANIC PHOTOVOLTAICS: TUNING THE CONJUGATED BACKBONE AND THE SUBSTITUENTS
Developing new conjugated polymer materials has been one of the most important driving forces for improving the performance of organic photovoltaics. This dissertation has been focused on structural design of polymers, including fine-tuning the backbone and the substituents of the polymers in order to adjust specific properties and improve the efficiency of organic photovoltaics. This dissertation details new methodologies to prepare the designed polymers and explores the structure-property relationship. We first developed regio-regular and regio-random terpolymers based on two parent copolymers with complementary absorption range. We found that adequate aggregation of these terpolymers is necessary for high performance photovoltaics. We then incorporated fluorine substituents into π linker thiophene units between the donor and the acceptor units and succeeded in controlling the positions and amount of fluorine substituents on the polymer backbone. The efficiency of the photovoltaics was remarkably improved by the fluorinated thiophene units. More importantly, we demonstrated the beneficial effects of fluorinated thiophene on improving the hole mobility and the importance of high hole mobility in improving fill factors of photovoltaics using eight structurally related polymers. Finally, in order to lower the bandgap of the polymers, we introduced strong electron withdrawing cyano group to the acceptor units. We systematically study the effect of cyano substitution on the properties of the polymers and the polymer solar cells by controlling the amount of cyano substituents. With single cyano substitution, a high device efficiency of ~ 8.6% was achieved for the monoCNTAZ polymer. All the works highlight the importance of optimizing the polymer structure to reach high solar cell performance.
Summer 2017
2017
Chemistry
Materials Science
Polymer chemistry
Conjugated polymers, Cyano substituted polymers, Fluorinated conjuated polymers, Organic photovoltaics, Terpolymers
eng
Doctor of Philosophy
Dissertation
University of North Carolina at Chapel Hill Graduate School
Degree granting institution
Chemistry
Wei
You
Thesis advisor
James
Cahoon
Thesis advisor
Simon
Meek
Thesis advisor
Frank
Leibfarth
Thesis advisor
Michel
Gagné
Thesis advisor
text
Qianqian
Zhang
Author
Department of Chemistry
College of Arts and Sciences
Design and Synthesis of Conjugated Polymers for Organic Photovoltaics: Tuning the Conjugated Backbone and the Substituents
Developing new conjugated polymer materials has been one of the most important driving forces for improving the performance of organic photovoltaics. This dissertation has been focused on structural design of polymers, including fine-tuning the backbone and the substituents of the polymers in order to adjust specific properties and improve the efficiency of organic photovoltaics. This dissertation details new methodologies to prepare the designed polymers and explores the structure-property relationship. We first developed regio-regular and regio-random terpolymers based on two parent copolymers with complementary absorption range. We found that adequate aggregation of these terpolymers is necessary for high performance photovoltaics. We then incorporated fluorine substituents into π linker thiophene units between the donor and the acceptor units and succeeded in controlling the positions and amount of fluorine substituents on the polymer backbone. The efficiency of the photovoltaics was remarkably improved by the fluorinated thiophene units. More importantly, we demonstrated the beneficial effects of fluorinated thiophene on improving the hole mobility and the importance of high hole mobility in improving fill factors of photovoltaics using eight structurally related polymers. Finally, in order to lower the bandgap of the polymers, we introduced strong electron withdrawing cyano group to the acceptor units. We systematically study the effect of cyano substitution on the properties of the polymers and the polymer solar cells by controlling the amount of cyano substituents. With single cyano substitution, a high device efficiency of ~ 8.6% was achieved for the monoCNTAZ polymer. All the works highlight the importance of optimizing the polymer structure to reach high solar cell performance.
Summer 2017
2017
Chemistry
Materials Science
Polymer chemistry
Conjugated polymers, Cyano substituted polymers, Fluorinated conjuated polymers, Organic photovoltaics, Terpolymers
eng
Doctor of Philosophy
Dissertation
University of North Carolina at Chapel Hill Graduate School
Degree granting institution
Chemistry
Wei
You
Thesis advisor
James
Cahoon
Thesis advisor
Simon
Meek
Thesis advisor
Frank
Leibfarth
Thesis advisor
Michel
Gagné
Thesis advisor
text
Qianqian
Zhang
Creator
Department of Chemistry
College of Arts and Sciences
Design and Synthesis of Conjugated Polymers for Organic Photovoltaics: Tuning
the Conjugated Backbone and the Substituents
Developing new conjugated polymer materials has been one of the most
important driving forces for improving the performance of organic photovoltaics. This
dissertation has been focused on structural design of polymers, including fine-tuning the
backbone and the substituents of the polymers in order to adjust specific properties and
improve the efficiency of organic photovoltaics. This dissertation details new
methodologies to prepare the designed polymers and explores the structure-property
relationship. We first developed regio-regular and regio-random terpolymers based on two
parent copolymers with complementary absorption range. We found that adequate aggregation
of these terpolymers is necessary for high performance photovoltaics. We then incorporated
fluorine substituents into π linker thiophene units between the donor and the acceptor
units and succeeded in controlling the positions and amount of fluorine substituents on
the polymer backbone. The efficiency of the photovoltaics was remarkably improved by the
fluorinated thiophene units. More importantly, we demonstrated the beneficial effects of
fluorinated thiophene on improving the hole mobility and the importance of high hole
mobility in improving fill factors of photovoltaics using eight structurally related
polymers. Finally, in order to lower the bandgap of the polymers, we introduced strong
electron withdrawing cyano group to the acceptor units. We systematically study the effect
of cyano substitution on the properties of the polymers and the polymer solar cells by
controlling the amount of cyano substituents. With single cyano substitution, a high
device efficiency of ~ 8.6% was achieved for the monoCNTAZ polymer. All the works
highlight the importance of optimizing the polymer structure to reach high solar cell
performance.
Summer 2017
2017
Chemistry
Materials Science
Polymer chemistry
Conjugated polymers, Cyano substituted polymers,
Fluorinated conjuated polymers, Organic photovoltaics, Terpolymers
eng
Doctor of Philosophy
Dissertation
University of North Carolina at Chapel Hill Graduate School
Degree granting
institution
Chemistry
Wei
You
Thesis advisor
James
Cahoon
Thesis advisor
Simon
Meek
Thesis advisor
Frank
Leibfarth
Thesis advisor
Michel
Gagné
Thesis advisor
text
Qianqian
Zhang
Creator
Department of Chemistry
College of Arts and Sciences
Design and Synthesis of Conjugated Polymers for Organic Photovoltaics: Tuning the Conjugated Backbone and the Substituents
Developing new conjugated polymer materials has been one of the most important driving forces for improving the performance of organic photovoltaics. This dissertation has been focused on structural design of polymers, including fine-tuning the backbone and the substituents of the polymers in order to adjust specific properties and improve the efficiency of organic photovoltaics. This dissertation details new methodologies to prepare the designed polymers and explores the structure-property relationship. We first developed regio-regular and regio-random terpolymers based on two parent copolymers with complementary absorption range. We found that adequate aggregation of these terpolymers is necessary for high performance photovoltaics. We then incorporated fluorine substituents into π linker thiophene units between the donor and the acceptor units and succeeded in controlling the positions and amount of fluorine substituents on the polymer backbone. The efficiency of the photovoltaics was remarkably improved by the fluorinated thiophene units. More importantly, we demonstrated the beneficial effects of fluorinated thiophene on improving the hole mobility and the importance of high hole mobility in improving fill factors of photovoltaics using eight structurally related polymers. Finally, in order to lower the bandgap of the polymers, we introduced strong electron withdrawing cyano group to the acceptor units. We systematically study the effect of cyano substitution on the properties of the polymers and the polymer solar cells by controlling the amount of cyano substituents. With single cyano substitution, a high device efficiency of ~ 8.6% was achieved for the monoCNTAZ polymer. All the works highlight the importance of optimizing the polymer structure to reach high solar cell performance.
Summer 2017
2017
Chemistry
Materials Science
Polymer chemistry
Conjugated polymers, Cyano substituted polymers, Fluorinated conjuated polymers, Organic photovoltaics, Terpolymers
eng
Doctor of Philosophy
Dissertation
University of North Carolina at Chapel Hill Graduate School
Degree granting institution
Chemistry
Wei
You
Thesis advisor
James
Cahoon
Thesis advisor
Simon
Meek
Thesis advisor
Frank
Leibfarth
Thesis advisor
Michel
Gagné
Thesis advisor
text
Qianqian
Zhang
Creator
Department of Chemistry
College of Arts and Sciences
Design and Synthesis of Conjugated Polymers for Organic Photovoltaics: Tuning the Conjugated Backbone and the Substituents
Developing new conjugated polymer materials has been one of the most important driving forces for improving the performance of organic photovoltaics. This dissertation has been focused on structural design of polymers, including fine-tuning the backbone and the substituents of the polymers in order to adjust specific properties and improve the efficiency of organic photovoltaics. This dissertation details new methodologies to prepare the designed polymers and explores the structure-property relationship. We first developed regio-regular and regio-random terpolymers based on two parent copolymers with complementary absorption range. We found that adequate aggregation of these terpolymers is necessary for high performance photovoltaics. We then incorporated fluorine substituents into π linker thiophene units between the donor and the acceptor units and succeeded in controlling the positions and amount of fluorine substituents on the polymer backbone. The efficiency of the photovoltaics was remarkably improved by the fluorinated thiophene units. More importantly, we demonstrated the beneficial effects of fluorinated thiophene on improving the hole mobility and the importance of high hole mobility in improving fill factors of photovoltaics using eight structurally related polymers. Finally, in order to lower the bandgap of the polymers, we introduced strong electron withdrawing cyano group to the acceptor units. We systematically study the effect of cyano substitution on the properties of the polymers and the polymer solar cells by controlling the amount of cyano substituents. With single cyano substitution, a high device efficiency of ~ 8.6% was achieved for the monoCNTAZ polymer. All the works highlight the importance of optimizing the polymer structure to reach high solar cell performance.
2017-08
2017
Chemistry
Materials Science
Polymer chemistry
Conjugated polymers, Cyano substituted polymers, Fluorinated conjuated polymers, Organic photovoltaics, Terpolymers
eng
Doctor of Philosophy
Dissertation
University of North Carolina at Chapel Hill Graduate School
Degree granting institution
Chemistry
Wei
You
Thesis advisor
James
Cahoon
Thesis advisor
Simon
Meek
Thesis advisor
Frank
Leibfarth
Thesis advisor
Michel
Gagné
Thesis advisor
text
Qianqian
Zhang
Creator
Department of Chemistry
College of Arts and Sciences
Design and Synthesis of Conjugated Polymers for Organic Photovoltaics: Tuning the Conjugated Backbone and the Substituents
Developing new conjugated polymer materials has been one of the most important driving forces for improving the performance of organic photovoltaics. This dissertation has been focused on structural design of polymers, including fine-tuning the backbone and the substituents of the polymers in order to adjust specific properties and improve the efficiency of organic photovoltaics. This dissertation details new methodologies to prepare the designed polymers and explores the structure-property relationship. We first developed regio-regular and regio-random terpolymers based on two parent copolymers with complementary absorption range. We found that adequate aggregation of these terpolymers is necessary for high performance photovoltaics. We then incorporated fluorine substituents into π linker thiophene units between the donor and the acceptor units and succeeded in controlling the positions and amount of fluorine substituents on the polymer backbone. The efficiency of the photovoltaics was remarkably improved by the fluorinated thiophene units. More importantly, we demonstrated the beneficial effects of fluorinated thiophene on improving the hole mobility and the importance of high hole mobility in improving fill factors of photovoltaics using eight structurally related polymers. Finally, in order to lower the bandgap of the polymers, we introduced strong electron withdrawing cyano group to the acceptor units. We systematically study the effect of cyano substitution on the properties of the polymers and the polymer solar cells by controlling the amount of cyano substituents. With single cyano substitution, a high device efficiency of ~ 8.6% was achieved for the monoCNTAZ polymer. All the works highlight the importance of optimizing the polymer structure to reach high solar cell performance.
2017
Chemistry
Materials Science
Polymer chemistry
Conjugated polymers, Cyano substituted polymers, Fluorinated conjuated polymers, Organic photovoltaics, Terpolymers
eng
Doctor of Philosophy
Dissertation
University of North Carolina at Chapel Hill Graduate School
Degree granting institution
Chemistry
Wei
You
Thesis advisor
James
Cahoon
Thesis advisor
Simon
Meek
Thesis advisor
Frank
Leibfarth
Thesis advisor
Michel
Gagné
Thesis advisor
text
2017-08
Qianqian
Zhang
Creator
Department of Chemistry
College of Arts and Sciences
Design and Synthesis of Conjugated Polymers for Organic Photovoltaics: Tuning the Conjugated Backbone and the Substituents
Developing new conjugated polymer materials has been one of the most important driving forces for improving the performance of organic photovoltaics. This dissertation has been focused on structural design of polymers, including fine-tuning the backbone and the substituents of the polymers in order to adjust specific properties and improve the efficiency of organic photovoltaics. This dissertation details new methodologies to prepare the designed polymers and explores the structure-property relationship. We first developed regio-regular and regio-random terpolymers based on two parent copolymers with complementary absorption range. We found that adequate aggregation of these terpolymers is necessary for high performance photovoltaics. We then incorporated fluorine substituents into π linker thiophene units between the donor and the acceptor units and succeeded in controlling the positions and amount of fluorine substituents on the polymer backbone. The efficiency of the photovoltaics was remarkably improved by the fluorinated thiophene units. More importantly, we demonstrated the beneficial effects of fluorinated thiophene on improving the hole mobility and the importance of high hole mobility in improving fill factors of photovoltaics using eight structurally related polymers. Finally, in order to lower the bandgap of the polymers, we introduced strong electron withdrawing cyano group to the acceptor units. We systematically study the effect of cyano substitution on the properties of the polymers and the polymer solar cells by controlling the amount of cyano substituents. With single cyano substitution, a high device efficiency of ~ 8.6% was achieved for the monoCNTAZ polymer. All the works highlight the importance of optimizing the polymer structure to reach high solar cell performance.
2017
Chemistry
Materials Science
Polymer chemistry
Conjugated polymers, Cyano substituted polymers, Fluorinated conjuated polymers, Organic photovoltaics, Terpolymers
eng
Doctor of Philosophy
Dissertation
University of North Carolina at Chapel Hill Graduate School
Degree granting institution
Chemistry
Wei
You
Thesis advisor
James
Cahoon
Thesis advisor
Simon
Meek
Thesis advisor
Frank
Leibfarth
Thesis advisor
Michel
Gagné
Thesis advisor
text
2017-08
Qianqian
Zhang
Creator
Department of Chemistry
College of Arts and Sciences
Design and Synthesis of Conjugated Polymers for Organic Photovoltaics: Tuning the Conjugated Backbone and the Substituents
Developing new conjugated polymer materials has been one of the most important driving forces for improving the performance of organic photovoltaics. This dissertation has been focused on structural design of polymers, including fine-tuning the backbone and the substituents of the polymers in order to adjust specific properties and improve the efficiency of organic photovoltaics. This dissertation details new methodologies to prepare the designed polymers and explores the structure-property relationship. We first developed regio-regular and regio-random terpolymers based on two parent copolymers with complementary absorption range. We found that adequate aggregation of these terpolymers is necessary for high performance photovoltaics. We then incorporated fluorine substituents into π linker thiophene units between the donor and the acceptor units and succeeded in controlling the positions and amount of fluorine substituents on the polymer backbone. The efficiency of the photovoltaics was remarkably improved by the fluorinated thiophene units. More importantly, we demonstrated the beneficial effects of fluorinated thiophene on improving the hole mobility and the importance of high hole mobility in improving fill factors of photovoltaics using eight structurally related polymers. Finally, in order to lower the bandgap of the polymers, we introduced strong electron withdrawing cyano group to the acceptor units. We systematically study the effect of cyano substitution on the properties of the polymers and the polymer solar cells by controlling the amount of cyano substituents. With single cyano substitution, a high device efficiency of ~ 8.6% was achieved for the monoCNTAZ polymer. All the works highlight the importance of optimizing the polymer structure to reach high solar cell performance.
2017
Chemistry
Materials Science
Polymer chemistry
Conjugated polymers, Cyano substituted polymers, Fluorinated conjuated polymers, Organic photovoltaics, Terpolymers
eng
Doctor of Philosophy
Dissertation
University of North Carolina at Chapel Hill Graduate School
Degree granting institution
Chemistry
Wei
You
Thesis advisor
James
Cahoon
Thesis advisor
Simon
Meek
Thesis advisor
Frank
Leibfarth
Thesis advisor
Michel
Gagné
Thesis advisor
text
2017-08
Qianqian
Zhang
Creator
Department of Chemistry
College of Arts and Sciences
Design and Synthesis of Conjugated Polymers for Organic Photovoltaics: Tuning the Conjugated Backbone and the Substituents
Developing new conjugated polymer materials has been one of the most important driving forces for improving the performance of organic photovoltaics. This dissertation has been focused on structural design of polymers, including fine-tuning the backbone and the substituents of the polymers in order to adjust specific properties and improve the efficiency of organic photovoltaics. This dissertation details new methodologies to prepare the designed polymers and explores the structure-property relationship. We first developed regio-regular and regio-random terpolymers based on two parent copolymers with complementary absorption range. We found that adequate aggregation of these terpolymers is necessary for high performance photovoltaics. We then incorporated fluorine substituents into π linker thiophene units between the donor and the acceptor units and succeeded in controlling the positions and amount of fluorine substituents on the polymer backbone. The efficiency of the photovoltaics was remarkably improved by the fluorinated thiophene units. More importantly, we demonstrated the beneficial effects of fluorinated thiophene on improving the hole mobility and the importance of high hole mobility in improving fill factors of photovoltaics using eight structurally related polymers. Finally, in order to lower the bandgap of the polymers, we introduced strong electron withdrawing cyano group to the acceptor units. We systematically study the effect of cyano substitution on the properties of the polymers and the polymer solar cells by controlling the amount of cyano substituents. With single cyano substitution, a high device efficiency of ~ 8.6% was achieved for the monoCNTAZ polymer. All the works highlight the importance of optimizing the polymer structure to reach high solar cell performance.
2017
Chemistry
Materials Science
Polymer chemistry
Conjugated polymers, Cyano substituted polymers, Fluorinated conjuated polymers, Organic photovoltaics, Terpolymers
eng
Doctor of Philosophy
Dissertation
Chemistry
Wei
You
Thesis advisor
James
Cahoon
Thesis advisor
Simon
Meek
Thesis advisor
Frank
Leibfarth
Thesis advisor
Michel
Gagne
Thesis advisor
text
2017-08
University of North Carolina at Chapel Hill
Degree granting institution
Qianqian
Zhang
Creator
Department of Chemistry
College of Arts and Sciences
Design and Synthesis of Conjugated Polymers for Organic Photovoltaics: Tuning the Conjugated Backbone and the Substituents
Developing new conjugated polymer materials has been one of the most important driving forces for improving the performance of organic photovoltaics. This dissertation has been focused on structural design of polymers, including fine-tuning the backbone and the substituents of the polymers in order to adjust specific properties and improve the efficiency of organic photovoltaics. This dissertation details new methodologies to prepare the designed polymers and explores the structure-property relationship. We first developed regio-regular and regio-random terpolymers based on two parent copolymers with complementary absorption range. We found that adequate aggregation of these terpolymers is necessary for high performance photovoltaics. We then incorporated fluorine substituents into π linker thiophene units between the donor and the acceptor units and succeeded in controlling the positions and amount of fluorine substituents on the polymer backbone. The efficiency of the photovoltaics was remarkably improved by the fluorinated thiophene units. More importantly, we demonstrated the beneficial effects of fluorinated thiophene on improving the hole mobility and the importance of high hole mobility in improving fill factors of photovoltaics using eight structurally related polymers. Finally, in order to lower the bandgap of the polymers, we introduced strong electron withdrawing cyano group to the acceptor units. We systematically study the effect of cyano substitution on the properties of the polymers and the polymer solar cells by controlling the amount of cyano substituents. With single cyano substitution, a high device efficiency of ~ 8.6% was achieved for the monoCNTAZ polymer. All the works highlight the importance of optimizing the polymer structure to reach high solar cell performance.
2017
Chemistry
Materials Science
Polymer chemistry
Conjugated polymers, Cyano substituted polymers, Fluorinated conjuated polymers, Organic photovoltaics, Terpolymers
eng
Doctor of Philosophy
Dissertation
University of North Carolina at Chapel Hill Graduate School
Degree granting institution
Chemistry
Wei
You
Thesis advisor
James
Cahoon
Thesis advisor
Simon
Meek
Thesis advisor
Frank
Leibfarth
Thesis advisor
Michel
Gagné
Thesis advisor
text
2017-08
Qianqian
Zhang
Creator
Department of Chemistry
College of Arts and Sciences
Design and Synthesis of Conjugated Polymers for Organic Photovoltaics: Tuning the Conjugated Backbone and the Substituents
Developing new conjugated polymer materials has been one of the most important driving forces for improving the performance of organic photovoltaics. This dissertation has been focused on structural design of polymers, including fine-tuning the backbone and the substituents of the polymers in order to adjust specific properties and improve the efficiency of organic photovoltaics. This dissertation details new methodologies to prepare the designed polymers and explores the structure-property relationship. We first developed regio-regular and regio-random terpolymers based on two parent copolymers with complementary absorption range. We found that adequate aggregation of these terpolymers is necessary for high performance photovoltaics. We then incorporated fluorine substituents into π linker thiophene units between the donor and the acceptor units and succeeded in controlling the positions and amount of fluorine substituents on the polymer backbone. The efficiency of the photovoltaics was remarkably improved by the fluorinated thiophene units. More importantly, we demonstrated the beneficial effects of fluorinated thiophene on improving the hole mobility and the importance of high hole mobility in improving fill factors of photovoltaics using eight structurally related polymers. Finally, in order to lower the bandgap of the polymers, we introduced strong electron withdrawing cyano group to the acceptor units. We systematically study the effect of cyano substitution on the properties of the polymers and the polymer solar cells by controlling the amount of cyano substituents. With single cyano substitution, a high device efficiency of ~ 8.6% was achieved for the monoCNTAZ polymer. All the works highlight the importance of optimizing the polymer structure to reach high solar cell performance.
2017
Chemistry
Materials Science
Polymer chemistry
Conjugated polymers; Cyano substituted polymers; Fluorinated conjuated polymers; Organic photovoltaics; Terpolymers
eng
Doctor of Philosophy
Dissertation
Chemistry
Wei
You
Thesis advisor
James
Cahoon
Thesis advisor
Simon
Meek
Thesis advisor
Frank
Leibfarth
Thesis advisor
Michel
Gagne
Thesis advisor
text
2017-08
University of North Carolina at Chapel Hill
Degree granting institution
Qianqian
Zhang
Creator
Department of Chemistry
College of Arts and Sciences
Design and Synthesis of Conjugated Polymers for Organic Photovoltaics: Tuning the Conjugated Backbone and the Substituents
Developing new conjugated polymer materials has been one of the most important driving forces for improving the performance of organic photovoltaics. This dissertation has been focused on structural design of polymers, including fine-tuning the backbone and the substituents of the polymers in order to adjust specific properties and improve the efficiency of organic photovoltaics. This dissertation details new methodologies to prepare the designed polymers and explores the structure-property relationship. We first developed regio-regular and regio-random terpolymers based on two parent copolymers with complementary absorption range. We found that adequate aggregation of these terpolymers is necessary for high performance photovoltaics. We then incorporated fluorine substituents into π linker thiophene units between the donor and the acceptor units and succeeded in controlling the positions and amount of fluorine substituents on the polymer backbone. The efficiency of the photovoltaics was remarkably improved by the fluorinated thiophene units. More importantly, we demonstrated the beneficial effects of fluorinated thiophene on improving the hole mobility and the importance of high hole mobility in improving fill factors of photovoltaics using eight structurally related polymers. Finally, in order to lower the bandgap of the polymers, we introduced strong electron withdrawing cyano group to the acceptor units. We systematically study the effect of cyano substitution on the properties of the polymers and the polymer solar cells by controlling the amount of cyano substituents. With single cyano substitution, a high device efficiency of ~ 8.6% was achieved for the monoCNTAZ polymer. All the works highlight the importance of optimizing the polymer structure to reach high solar cell performance.
2017
Chemistry
Materials Science
Polymer chemistry
Conjugated polymers, Cyano substituted polymers, Fluorinated conjuated polymers, Organic photovoltaics, Terpolymers
eng
Doctor of Philosophy
Dissertation
University of North Carolina at Chapel Hill Graduate School
Degree granting institution
Chemistry
Wei
You
Thesis advisor
James
Cahoon
Thesis advisor
Simon
Meek
Thesis advisor
Frank
Leibfarth
Thesis advisor
Michel
Gagne
Thesis advisor
text
2017-08
Qianqian
Zhang
Creator
Department of Chemistry
College of Arts and Sciences
Design and Synthesis of Conjugated Polymers for Organic Photovoltaics: Tuning the Conjugated Backbone and the Substituents
Developing new conjugated polymer materials has been one of the most important driving forces for improving the performance of organic photovoltaics. This dissertation has been focused on structural design of polymers, including fine-tuning the backbone and the substituents of the polymers in order to adjust specific properties and improve the efficiency of organic photovoltaics. This dissertation details new methodologies to prepare the designed polymers and explores the structure-property relationship. We first developed regio-regular and regio-random terpolymers based on two parent copolymers with complementary absorption range. We found that adequate aggregation of these terpolymers is necessary for high performance photovoltaics. We then incorporated fluorine substituents into π linker thiophene units between the donor and the acceptor units and succeeded in controlling the positions and amount of fluorine substituents on the polymer backbone. The efficiency of the photovoltaics was remarkably improved by the fluorinated thiophene units. More importantly, we demonstrated the beneficial effects of fluorinated thiophene on improving the hole mobility and the importance of high hole mobility in improving fill factors of photovoltaics using eight structurally related polymers. Finally, in order to lower the bandgap of the polymers, we introduced strong electron withdrawing cyano group to the acceptor units. We systematically study the effect of cyano substitution on the properties of the polymers and the polymer solar cells by controlling the amount of cyano substituents. With single cyano substitution, a high device efficiency of ~ 8.6% was achieved for the monoCNTAZ polymer. All the works highlight the importance of optimizing the polymer structure to reach high solar cell performance.
2017
Chemistry
Materials Science
Polymer chemistry
Conjugated polymers; Cyano substituted polymers; Fluorinated conjuated polymers; Organic photovoltaics; Terpolymers
eng
Doctor of Philosophy
Dissertation
University of North Carolina at Chapel Hill Graduate School
Degree granting institution
Wei
You
Thesis advisor
James
Cahoon
Thesis advisor
Simon
Meek
Thesis advisor
Frank
Leibfarth
Thesis advisor
Michel
Gagne
Thesis advisor
text
2017-08
Zhang_unc_0153D_17235.pdf
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