ETDs

This collection includes most of the ASU Theses and Dissertations from 2011 to present. ASU Theses and Dissertations are available in downloadable PDF format; however, a small percentage of items are under embargo. Information about the dissertations/theses includes degree information, committee members, an abstract, supporting data or media.

In addition to the electronic theses found in the ASU Digital Repository, ASU Theses and Dissertations can be found in the ASU Library Catalog.

Dissertations and Theses granted by Arizona State University are archived and made available through a joint effort of the ASU Graduate College and the ASU Libraries. For more information or questions about this collection contact or visit the Digital Repository ETD Library Guide or contact the ASU Graduate College at gradformat@asu.edu.

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High Efficiency Monolithic Solar Cell with Reduced Forward Bias Current: Theory, Design and Application

Description
As the single-junction silicon solar cell is approaching its theoretical efficiency limits, the loss from shading and resistance is gaining increasing attention. The metal grid pattern may cause an efficiency loss up to 1–3%abs (absolute percentage) depending on the grid’s materials and structure.Many attempts have been proposed to reduce the…

As the single-junction silicon solar cell is approaching its theoretical efficiency limits, the loss from shading and resistance is gaining increasing attention. The metal grid pattern may cause an efficiency loss up to 1–3%abs (absolute percentage) depending on the grid’s materials and structure.Many attempts have been proposed to reduce the loss caused by the contacts and module. Among them, the monolithic solar cell, which is a solar cell with multiple string cells on the same wafer and connected in a series, presents advantages of low output current, busbar-free contact, minimized interconnection space, and ohmic loss reduction. However, this structure also introduces a lateral forward bias current through the base region, which severely degrades the cell’s performance. In addition, this interconnection in the base region has partially shunted certain solar cells in the monolithic cell, which created a mismatch between string cells. For the last few decades, researchers have used different methods such as etching trenches or enlarging the distance between the neighboring string cells to solve this problem. However, these methods were both ineffective and defective. In this work, a novel method of suppressing the lateral forward bias current is proposed. By adding a very high surface recombination to the mid-region between the string cells, the carrier density in the mid-region can be decreased close to the doping density. Thus, the resistivity in the mid-region can be increased tenfold or more. As a result, the lateral forward bias current is greatly reduced. Other methods to reduce lateral forward bias current include optimizing the width of the mid-region, shading the mid-region, reducing the base doping and base thickness which can be used to reduce the mismatch as well. Another method has been proposed to calculate the minimum efficiency loss of a monolithic cell compared to the baseline solar cell. As a result, the monolithic cell could potentially gain more advantages over the baseline solar cells with a thinner and low-doped wafer. A monolithic solar cell with innovative designs is presented in this work which shows an efficiency that is potentially higher than that of normal solar cells.
ContributorsXue, Shujian (Author) / Bowden, Studart (Thesis advisor) / Goodnick, Stephen (Committee member) / Vasileska, Dragica (Committee member) / Goryll, Michael (Committee member) / Arizona State University (Publisher)
Created2022
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Silver Recovery through a Fluoride Chemistry for Solar Module Recycling

Description
With the demand growing for more sustainable forms of energy in replacement of fossil fuels, a major obstacle arises in the end-of life solar modules that are disposed of in landfills. Aside from the hazardous materials, silicon solar modules contain valuable and scarce materials such as silver. Silver is used…

With the demand growing for more sustainable forms of energy in replacement of fossil fuels, a major obstacle arises in the end-of life solar modules that are disposed of in landfills. Aside from the hazardous materials, silicon solar modules contain valuable and scarce materials such as silver. Silver is used in many industries and many applications therefore the recycling and recovering of it is financially beneficial. The purpose of this research was to achieve high purity and recovery of silver using hydrofluoric acid. The following work presents the feasibility of silver recovery through the process of leaching and electrowinning by examining the percent recovery and cathodic coulombic efficiency, followed by a chemical analysis to determine the purity. Varying conditions in leaching and electrowinning parameters are conducted in a synthetic solution to determine the effect on silver recovery and cathodic coulombic efficiency. It was determined that the silver recovery was dependent on the applied potential, system configuration and time. The system is capable of recovery rates of over 95% at -1 V. The system is further tested on solar cells to prove that silver can be recovered. There was over 99% purity from the experiments conducted in synthetic solution and from solar cells. Additionally, a circular chemistry is proposed that allows the reuse of hydrofluoric acid for leaching and electrowinning.
ContributorsChen, Theresa (Author) / Tao, Meng (Thesis advisor) / Deng, Shuguang (Committee member) / Goryll, Michael (Committee member) / Arizona State University (Publisher)
Created2024