Tilted Columnar Thin Film Coatings With Anisotropic Light Scattering Properties for Solar Energy Applications
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Authors
Sadeghi-Khosravieh, Saba
Date
2016-08-09
Type
thesis
Language
eng
Keyword
Glancing Angle Deposition , Bidirectional Reflectance Distribution Function , Dye-Sensitized Solar Cells , Directional Scattering
Alternative Title
Abstract
The main goal of this thesis is to show the versatility of glancing angle deposition
(GLAD) thin films in applications. This research is first focused on studying the
effect of select deposition variables in GLAD thin films and secondly, to demonstrate
the flexibility of GLAD films to be incorporated in two different applications: (1) as
a reflective coating in low-level concentration photovoltaic systems, and (2) as an
anode structure in dye-sensitized solar cells (DSSC).
A particular type of microstructure composed of tilted micro-columns of titanium
is fabricated by GLAD. The microstructures form elongated and fan-like tilted
micro-columns that demonstrate anisotropic scattering.
The thin films texture changes from fiber texture to tilted fiber texture by increasing
the vapor incidence angle. At very large deposition angles, biaxial texture forms.
The morphology of the thin films deposited under extreme shadowing condition
and at high temperature (below recrystallization zone) shows a porous and inclined
micro-columnar morphology, resulting from the dominance of shadowing over
adatom surface diffusion.
The anisotropic scattering behavior of the tilted Ti thin film coatings is quantified
by bidirectional reflectance distribution function (BRDF) measurements and is
found to be consistent with reflectance from the microstructure acting as an array
of inclined micro-mirrors that redirect the incident light in a non-specular reflection.
A silver-coating of the surface of the tilted-Ti micro-columns is performed to enhance the total reflectance of the Ti-thin films while keeping the anisotropic scattering
behavior. By using such coating is as a booster reflector in a laboratory-scale low-level
concentration photovoltaic system, the short-circuit current of the reference silicon
solar cell by 25%.
Finally, based on the scattering properties of the tilted microcolumnar
microstructure, its scattering effect is studied as a part of titanium dioxide
microstructure for the anode in DSSCs. GLAD-fabricated TiO2 microstructures
for the anode in a DSSC, consisting of vertical micro-columns, and combined
vertical topped with tilted micro-columns are compared. The solar cell with the
two-part microstructure shows the highest monochromatic incident photon to
current efficiency with 20% improvement compared to the vertical microstructure,
and the efficiency of the cell increases from 1.5% to 2% due to employing the
scattering layer.
Description
Thesis (Ph.D, Mechanical and Materials Engineering) -- Queen's University, 2016-08-08 17:39:09.119
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Publisher
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Queen's University's Thesis/Dissertation Non-Exclusive License for Deposit to QSpace and Library and Archives Canada
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Copying and Preserving Your Thesis
This publication is made available by the authority of the copyright owner solely for the purpose of private study and research and may not be copied or reproduced except as permitted by the copyright laws without written authority from the copyright owner.
This publication is made available by the authority of the copyright owner solely for the purpose of private study and research and may not be copied or reproduced except as permitted by the copyright laws without written authority from the copyright owner.
This publication is made available by the authority of the copyright owner solely for the purpose of private study and research and may not be copied or reproduced except as permitted by the copyright laws without written authority from the copyright owner.
ProQuest PhD and Master's Theses International Dissemination Agreement
Intellectual Property Guidelines at Queen's University
Copying and Preserving Your Thesis
This publication is made available by the authority of the copyright owner solely for the purpose of private study and research and may not be copied or reproduced except as permitted by the copyright laws without written authority from the copyright owner.
This publication is made available by the authority of the copyright owner solely for the purpose of private study and research and may not be copied or reproduced except as permitted by the copyright laws without written authority from the copyright owner.
This publication is made available by the authority of the copyright owner solely for the purpose of private study and research and may not be copied or reproduced except as permitted by the copyright laws without written authority from the copyright owner.