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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

Abstract

Solar energy is a viable clean form of renewable energy which can be utilized by converting light energy into electrical energy through solar cells based on inorganic and organic materials. Bulk heterojunction solar cell is a type of organic solar cell that has potential for low cost manufacturing with power conversion efficiency of 10%. Kinetic Monte Carlo method is an effective method to study mobility, recombination and internal quantum efficiency in bulk heterojunction solar cells as reported in literature. However, a comprehensive simulation of dark and illuminated current voltage characteristics of 3 D polymer bulk heterojunction solar cells using Kinetic Monte Carlo is lacking. The objectives of this thesis were to develop a new computational model that can simulate current voltage characteristics of bulk heterojunction solar cell using Kinetic Monte Carlo methods and use the model to study effect of interfacial buffer layer in IV characteristics of bulk heterojunction solar cell. The major physical processes such as: exciton generation/dissociation/recombination, charge hopping/recombination and charge injection/extraction mechanisms were incorporated in a Kinetic Monte Carlo simulation using first principle approach. A bulk heterojunction device structure was generated using Metropolis Monte Carlo algorithm, with an active layer sandwiched between electron/hole transport layers with randomly distributed localized sites and Gaussian distributed HOMO/LUMO energy level. The dark IV increased while the performance of solar cell decreased with increasing recombination rates. It was found that a buffer layer of 2 nm at the donor/acceptor interface for case of a recombination rate of 1ps-1, showed as much as 20%, 13% and 83% increase in VOC, JSC and efficiency respectively demonstrating that buffer layer at the donor/acceptor interfaces can enhance the performance of bulk heterojunction solar cells. The origin of dark IV was due to recombination of electrons and holes at donor/acceptor interface. Interface of active layer and transport layer collecting/injecting lower mobility charge particles were shown to be the primary source of recombination losses. The model can incorporate various parameters such as mobility, temperature, morphology, band offsets, etc and show its impact on device performance parameters which can help in optimization of solar cells.

Library of Congress Subject Headings

Solar cells -- Properties
Heterojunctions
Monte Carlo method

Description

Includes bibliographical references (pages 86-96)

Format

application/pdf

Number of Pages

109

Publisher

South Dakota State University

Rights

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

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