Electrochemical studies of III-V heterojunctions and nanowires
Abstract/Contents
- Abstract
- III-V semiconductors exhibit light absorption and charge transport properties that make them ideal for solar energy conversion. However, these materials have been relatively unexplored, as compared to silicon and metal oxides, for photoelectrochemical water splitting. They have also not seen much development in photovoltaics apart from expensive and resource-hungry multijunction architectures. The focus of this work is in the growth of III-V thin film heterojunctions and nanowires, and in electrochemical analysis as an evaluation as electrodes in photoelectrochemical energy conversion and in photovoltaic devices. The first part of this work focuses on the design of two epitaxial heterojunction III-V stacks: InGaP grown on GaAs, and GaP grown on Si. The photovoltaic parameters of these heterojunctions are extracted, and solar-driven hydrogen evolution is demonstrated. Additionally, a new material, AlPN, is grown on GaP. Despite its apparent lack of crystallinity, it demonstrates photoactivity in the visible light range. The second part of this work demonstrates a reduction photocurrent in III-V phosphide nanowires that, due to their reduced dimensionality, can aid in the performance of solar-to-hydrogen systems. Controlled non-aqueous measurements are performed to examine the reduction photocurrent generated in the nanowires, and electrochemical impedance measurements are used to characterize the energetics and electrostatics in the junction created between the nanowires and the electrolyte. Novel phenomena are observed in the materials growth of phosphide nanowires on GaAs, specifically substrate tuning of the growth directions for GaP nanowires, and the formation of an InGaAs interlayer during InP nanowire growth. The third and final part of this work investigates the development of III-V nitride materials for solar energy conversion. With growth control, various micro and nanoscale morphologies of GaN-on-Si heterojunctions are created to drive an oxidation photocurrent in non-aqueous environments. This photocurrent shows that a structured nanowire/film electrode exhibits promising performance in the context of materials usage, and impedance measurements help to build a band diagram of the Si/GaN/electrolyte junction created for all electrodes under study. Single crystal InN nanowires are grown with different morphologies and generate a photovoltage under solar illumination within an electrochemical junction, opening up research in using high-indium InGaN alloys for solar cell and photoelectrode applications.
Description
| Type of resource | text |
|---|---|
| Form | electronic; electronic resource; remote |
| Extent | 1 online resource. |
| Publication date | 2015 |
| Issuance | monographic |
| Language | English |
Creators/Contributors
| Associated with | Parameshwaran, Vijay |
|---|---|
| Associated with | Stanford University, Department of Electrical Engineering. |
| Primary advisor | Clemens, B. M. (Bruce M.) |
| Thesis advisor | Clemens, B. M. (Bruce M.) |
| Thesis advisor | Bent, Stacey |
| Thesis advisor | Harris, J. S. (James Stewart), 1942- |
| Advisor | Bent, Stacey |
| Advisor | Harris, J. S. (James Stewart), 1942- |
Subjects
| Genre | Theses |
|---|
Bibliographic information
| Statement of responsibility | Vijay Parameshwaran. |
|---|---|
| Note | Submitted to the Department of Electrical Engineering. |
| Thesis | Thesis (Ph.D.)--Stanford University, 2015. |
| Location | electronic resource |
Access conditions
- Copyright
- © 2015 by Vijay Parameshwaran
- License
- This work is licensed under a Creative Commons Attribution Non Commercial 3.0 Unported license (CC BY-NC).
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