(Georgia Institute of Technology, 2014-11-17)
Zhang, Xiaodan
Cellulose is the most abundant biopolymer in the world and the main
component of paper. Modern society requires electronic devices to be more
flexible and environmental friendly, which makes cellulose as a good
candidate for the next generation of green electronics. However, lots of
researches employed “paper-like” petroleum-based polymers to fabricate
electronics rather than using real cellulose paper. Cellulose, as a
representative of environmental friendly materials, caught into people's
attention because of its sustainable nature, ease of functionality,
flexibility and tunable surface properties, etc. There are some general
challenges about using cellulose for electronics, such as its
non-conductivity, porosity and roughness, but these features can be taken
advantages of on certain occasions. This thesis focuses on the study of
cellulose-based electronic devices by chemical or physical modification of
microfibrillated cellulose (MFC). Particularly, three electronic devices
were fabricated, including ionic diodes, electric double layer
supercapacitors, pseudocapacitors. In addition, a rational design of
dye-sensitized solar cell was investigated, although it was not directly
cellulose-based, it led the way to the next generation of cellulose-based
solar cells. The extraordinary physical and chemical properties of MFC were
successfully leveled in those devices, in addition, inspiring and effective
fabrication methods were proposed and carried out to solve the major
problems faced by paper-based electronics, such as conductivity,
flexibility, packaging and designs.
(Georgia Institute of Technology, 2010-05-20)
Weintraub, Benjamin A.
As humanly engineered materials systems approach the atomic scale, top-down manufacturing approaches breakdown and following nature's example, bottom-up or self-assembly methods have the potential to emerge as the dominant paradigm. Synthesis of one-dimensional nanomaterials takes advantage of such self-assembly manufacturing
techniques, but until now most efforts have relied on high temperature vapor phase schemes which are limited in scalability and compatibility with organic materials. The solution-phase approach is an attractive low temperature alternative to overcome these
shortcomings. To this end, this thesis is a study of the rationale solution-phase synthesis
of ZnO nanowires and applications in photovoltaics.
The following thesis goals have been achieved: rationale synthesis of a single
ZnO nanowire on a polymer substrate without seeding, design of a wafer-scale technique
to control ZnO nanowire array density using layer-by-layer polymers, determination of
optimal nanowire field emitter density to maximize the field enhancement factor, design
of bridged nanowires across metal electrodes to order to circumvent post-synthesis manipulation steps, electrical characterization of bridged nanowires, rationale solution-phase synthesis of long ZnO nanowires on optical fibers, fabrication of ZnO nanowire dye-sensitized solar cells on optical fibers, electrical and optical characterization of solar cell devices, comparison studies of 2-D versus 3-D nanowire dye-sensitized solar cell devices, and achievement of 6-fold solar cell power conversion efficiency enhancement using a 3-D approach. The thesis results have implications in nanomanufacturing scale-up and next generation photovoltaics.