Thesis
Synthesis, characterization, and application of vanadium oxide nanowires
Washington State University
Master of Science (MS), Washington State University
2016
Handle:
https://hdl.handle.net/2376/103401
Abstract
A simple ambient pressure growth process is reported for the first time for the synthesis of vanadium (II) oxide (VO) nanowires with an average width of 65 nm and up to 5 mm in length for growth at 1000 ᵒC for 3 hours. The VO nanowire growth was catalyzed on a gold coated silicon substrate using a single heat zone furnace with argon as the carrier gas. An increase in nanowire width was observed with an increase in the temperature. A nine-fold increase in the number density of the nanowires was observed when the heating time was changed from 30 mins to 3 hours. Such a scheme enables wider use of VO nanowires in critical applications. A root growth mechanism for the facile synthesis of VO nanowires is presented. The investigation of the impact of flow rate and catalyst on nanowire growth indicates bimodal growth. Early in the growth process, VO nanowires tend to grow horizontally along the substrate surface and reach a critical density. Vertically aligned nanowires extrude unhindered from catalyst alloy islands. The evidence presented here indicates that (a) a metal catalyst is required for the vertical growth of VO nanowires in this setup, and (b) the horizontal growth observed is independent of the metal catalyst. Also a general system for mapping the input variables to output parameters for growth systems is proposed. Dye sensitized solar cells (DSSC) have great potential to address the need for renewable energy. In this research, VO nanowires were used as an improved charge recombination blocking layer in dye-sensitized solar cells to reduce back charge recombination. Cyclic voltammetry shows a larger charge build up in the VO treated solar cell. Further, electrochemical impedance spectroscopy shows an increase in the shunt resistance from 130 Ω to 210 Ω. The addition of VO nanowires to the DSSC increased its efficiency by a factor of 3.9 with the Voc increasing from 33 mV to 89 mV and Isc increasing from 9.5 µA to 12.4 µA. The results indicate the strong potential of VO nanowires as a recombination blocking layer and a surface area enhancer.
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Details
- Title
- Synthesis, characterization, and application of vanadium oxide nanowires
- Creators
- Jesse Steven Kysar
- Contributors
- Praveen K. Sekhar (Degree Supervisor)
- Awarding Institution
- Washington State University
- Academic Unit
- Electrical Engineering and Computer Science, School of
- Theses and Dissertations
- Master of Science (MS), Washington State University
- Publisher
- Washington State University; [Pullman, Washington] :
- Identifiers
- 99900525153801842
- Language
- English
- Resource Type
- Thesis