Date of Graduation

Summer 2013

Degree

Master of Science in Materials Science

Department

Physics, Astronomy and Materials Science

Committee Chair

Saibal Mitra

Keywords

tungsten oxide, pulsed laser deposition, electrochromic, thin film device, super ionic conductor, solid electrolyte, neutron diffraction

Subject Categories

Materials Science and Engineering

Abstract

In order to fabricate layered electrochromic devices capable of reversibly changing color in response to applied voltage, pulsed laser deposition was used to deposit thin films of tungsten oxide on fluorine doped tin oxide substrates.The thin films were deposited at room temperature in an O2 atmosphere of the order of 10-1 mbar on FTO/glass substrates using a KrF pulsed laser source. XRD analysis confirmed the resulting films to be amorphous and UV-Vis spectroscopy confirmed transparency. Raman shift confirms non-crystalline WO3 presence. Electrochromic devices were connected to a cyclic voltammetry system to regulate voltage sweeps, investigate charge transport, response time and reversibility of color/bleached states. Scanning electron microscopy was performed on the films post device operation to examine the surface topography and composition. Raman spectroscopy and XRD was performed post device films to investigate any changes in the films. Li+ ion conducting glasses of composition xLi2SO4 - (1-x)[0.50Li2O-0.5(2NH4H2PO2)) were characterized using resistivity measurements and neutron diffraction experiments to evaluate them as suitable substitutes for the electrolyte in the electrochromic devices. Formation of crystallites above 400°;C has been observed which is understood to hamper Li+ ion mobility, resulting in reduced performance of the electrolyte. The acid based electrochromic devices have exhibited superior reversibility.

Copyright

© Syed Ali Zaidi

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