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Document Type

Thesis - University Access Only

Award Date

2013

Degree Name

Master of Science (MS)

Department / School

Electrical Engineering and Computer Science

First Advisor

Mahdi Farrokh Baroughi

Second Advisor

David Galipeau

Abstract

Dye Sensitized Solar Cells (DSSCs) have attracted much attention as a potential alternative to conventional solar cells due to its simple fabrication methods, low material cost, high absorption coefficient, flexibility, light weight etc. However, the low conversion efficiency of DSSC is hindering its commercialization. The loss mechanisms associated with the performance of the cells, which lead to low power conversion efficiency are not clearly understood and quantified in dye sensitized solar cells. Thus, there is a need for a charge transport model that relates the performance characteristics of DSSC to the material and device parameters and provides guidance to experimentalists regarding the performance limiting factors in a real device. The objective of this research was to develop a robust charge transport model for DSSC that incorporates the internal physical processes in charge transport and lead to a quantifiable understanding of loss mechanisms. A charge transfer model was developed that incorporated electron capture/emission and oxidation/reduction processes mediated by the deep level interfacial trap states. The charge transport was modeled through the formulation of electron conservation law in the nanoporous TiO2 network for both steady state and time dependent conditions. Newton Raphson method was used to solve the charge transport model which was a 1D nonlinear second order differential equation. The photovoltaic characteristics of the DSSCs such as external quantum efficiency (EQE) and dark and illuminated IV, were simulated and the performance characteristics such as open circuit voltage, short circuit current and activation energy were obtained for the devices. The model was validated through a series of measurements on fabricated DSSCs. The activation energy of charge transport derived from temperature dependent dark IV characteristics for simulated and experimental DSSCs were 0.93 eV and 0.9 eV respectively. The Simulation concluded that in cells with low interface quality, interface treatment leads to enhance Jsc and Voc, while in high quality DSSCs, interface treatments lead to enhanced Voc and device efficiency. Good agreement between the measurement and simulation results confirms that the dominating charge transport pathway in DSSCs is the trap-assisted interfacial charge transfer at TiO2/dye/electrolyte interface.

Library of Congress Subject Headings

Dye-sensitized solar cells
Charge transfer
Interfaces(Physical sciences)

Description

Includes bibliographical references (pages 79-91)

Format

application/pdf

Number of Pages

103

Publisher

South Dakota State University

Rights

In Copyright - Educational Use Permitted
http://rightsstatements.org/vocab/InC-EDU/1.0/

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