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Document Type

Dissertation - University Access Only

Award Date

2014

Degree Name

Doctor of Philosophy (PhD)

Department

Electrical Engineering and Computer Science

First Advisor

Qi Hua Fan

Abstract

Thin film Si solar cells are expected to meet the future demand of hundreds of gigawatts due to the vast abundance of Si feedstock, non-toxicity, less susceptibility to moisture, fewer encapsulation challenges, and mature processing methods. High efficiency thin film Si solar cells can be obtained using microcrystalline Si thin films and highly reflective and light scattering back reflectors. However there is a need for methods that can rapidly and uniformly produce large-area Si nanoparticle-based films that can be re-crystallized into microcrystalline Si, and rapidly produce large-area TiO2 nanoparticlebased (pigment) back reflectors compatible with roll-to-roll processing, high density plasmas, and high vacuum environments. Si nanoparticle suspension stability was improved from a few minutes to a few days with the addition of alcohol. An alcohol reverse micelle stability mechanism was proposed. Dense Si nanoparticle-based films were produced without agglomerations at lower electrophoretic deposition voltages. Compared to as-deposited Si nanoparticle films, the photonic cured films were comprised of mostly larger globules with up to micron sized diameters, suggesting that Si nanoparticles were melted into liquid form and re-solidified when cooled into larger globules. Raman spectra indicated that the Si globules were comprised of low-defect, high-crystallinity Si.A pigment suspension comprised of a spin-on-glass solution and 410 nm TiO2 pigments (DuPont) remained milky white for multiple days with minimal sedimentation indicating high stability. The reflection spectrum of TiO2 pigment-based back reflector was higher or comparable to Ag/ZnO. The spectra of the pigment-based back reflector was diffuse. In comparison, the diffuse reflection of the Ag/ZnO and Al/ZnO back reflectors was significantly lower than their total reflection and about a third less than the TiO2 pigment-based back reflector. The highest solar cell photocurrent and efficiency was achieved with the TiO2 pigment-based back reflector followed by Ag/ZnO and Al/ZnO. The resistivity of the pigment-based back reflector/hole/ITO nanoparticle films was on the order of 102 to 104 Ω·cm. A 4 inch wide by 6 feet TiO2 pigment-based back reflector was produced by continuous deposition roll-to-roll and did not show cracking or peel off damage while being flexed or rewound on the take up roller.

Library of Congress Subject Headings

Solar cells
Thin films
Electrophoretic deposition
Nanoparticles

Description

Includes bibliographical references (pages 109-123)

Format

application/pdf

Number of Pages

131

Publisher

South Dakota State University

Rights

In Copyright - Non-Commercial Use Permitted
http://rightsstatements.org/vocab/InC-NC/1.0/

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