Document Type

Dissertation - University Access Only

Award Date

2012

Degree Name

Doctor of Philosophy (PhD)

Department / School

Electrical Engineering and Computer Science

First Advisor

Hongshan He

Abstract

Dye-sensitized solar cells (DSCs) have emerged as a cost effective alternative to silicon solar cells. Typically DSCs use mesoporous titanium dioxide for electron transport which latter was realized to contribute towards recombination losses. One-dimensional nanotubeshave emerged as a potential alternative to the mesoporous TiO2 for providing one-dimensional electron transport and reduced recombination. N anotube based DSCs have several challenges such as the growth of highly ordered nanotubes, and optimization of their morphology to obtain efficiencies greater than those reported for nanoparticle based DSCs. The objective of this research was to develop a fast and reproducible technique to grow highly ordered nanotubes; use the nanotubes to fabricate a front illuminated solar cell and investigate the effect of nanotube morphology on the PV performance for higher efficiency. TiO2 nanotubes were grown by a potentistatic anodization technique. The morphology of nanotubes was studied using scanning electron microscopy (SEM). A comparative study of back illuminated and front illuminated nanotube based DSCs and the effect of different orientations of nanotubes on DSC performance was investigated using 1-V, EQE and electrochemicalimpedance spectroscopy (EIS) techniques. The crystalline phases of annealed Ti02 were investigated by XRD. V A novel chemical pretreatment for titanium substrates that allows the growth of highly oriented Ti02 nanotubes was developed. A novel liftoff technique for removing nanotube films from Ti substrates was developed along with a novel low temperature and high pressure technique for the fixation of this nanotube film on to transparent conducting· glass substrates to fabricate front illuminated _dye-sensitized solar cells. A novel DSC structure with open end down nanotubes for front illuminated cell was developed. This configuration had significantly higher efficiency (6.5%) than a closed end down nanotube structure (3.5%). Nanotube based DSCs had higher efficiency (6.5%) than similar cell with nanoparticles (5.4%) which suggests that nanotubes are more promising structure than the nanoparticle based DSCs due to less recombination along the nanotube length.In order to further improve the efficiency of nanotube based DSCs, dye loading in nanotube films should be increased by filling nanotubes with Ti02 nanoparticles.

Library of Congress Subject Headings

Nanotubes
Titanium dioxide
Dye-sensitized solar cells

Publisher

South Dakota State University

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Rights Statement

In Copyright