Graduation Year

2022

Document Type

Dissertation

Degree

Ph.D.

Degree Name

Doctor of Philosophy (Ph.D.)

Degree Granting Department

Electrical Engineering

Major Professor

Arash Takshi, Ph.D.

Committee Member

Elias Stefanakos, Ph.D.

Committee Member

Sylvia Thomas, Ph.D.

Committee Member

Manoj Ram, Ph.D.

Committee Member

Ryan Toomey, Ph.D.

Keywords

Flexible Device, Hybrid Device, Photoactive Electrolyte, Solar Cell, Supercapacitor, Thread

Abstract

Over the past few years, smart textiles and wearable technologies have received tremendous attention due to their functionalities and characteristics, which could be used in a variety of ways in healthcare, sports/leisure, fashion, military, personal protective, and energy applications. These technologies depend on self-power systems, which require energy sources (e.g., batteries, supercapacitors, and solar cells) to power their projected functionalities in the future. Therefore, fabricating energy harvesting cells (i.e., solar cells) and energy storage cells (i.e., batteries and supercapacitors) in the form of fibers are promising solutions for powering wearable electronics due to their unique features such as flexibility and stretchability.

In this dissertation work, several projects and research works were carried out to fabricate and characterize two-terminal energy harvesting and storage devices based on a photoactive gel electrolyte. First, the photoactive composite gel containing polyaniline (PANI) was investigated by studying the effect of aniline (ANI) concentration in the bulk of the gel electrolyte on the impedance, capacitance, and photovoltaic performance of the devices. It was found that 0.3 M of ANI improves the energy storage and reduces the device's impedance, while the photovoltaic (PV) performance can be improved with 0.2 M of ANI.

The performance of the two-terminal hybrid cell can also be enhanced by optimizing the counter electrode materials. As a part of this research work, the impact of the counter electrode on the electrochemical and photovoltaic properties of the hybrid cell was considered by studying various counter electrodes made from carbon nanotubes (CNTs), a conducting polymer, carbon monolithic, and carbon fibers. The results showed improvement in the hybrid cell's impedance, self-discharge, and energy storage performance with PEDOT:PSS as a conducting polymer. However, improving the capacitance of the hybrid cell with carbon fiber fabric and carbon monolithic electrodes negatively affects the PV performance and vice versa.

Moreover, three different symmetric thread-based supercapacitors with twisted structures were fabricated in order to study the electrochemical properties of the conductive threads (i.e., Jameco, JL, and BCP) and the impact of the structure on the device performance. The results revealed that the Jameco-based device provides a higher capacitance, and the capacitance is directly related to the number of twists due to the uniformity of the Jameco thread surface.

Finally, a flexible fiber-shaped hybrid device was successfully fabricated using the photoactive gel electrolyte and two conductive threads. The device was also examined with three different anode electrodes (i.e., Ny66-Ag, Ny66-Ag/CNT, and Ny66-Ag/CNT/ZnO-NWs) to improve the energy storage and PV response of the device. The results showed that the energy storage improved with the Ny66-Ag/CNT electrode, while the PV response increased with the Ny66-Ag/CNT/ZnO-NWs electrode.

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