Thesis (M.S.)--California Polytechnic State University, 2008. / "June 2008." "In partial fulfillment of the requirements for the degree of Master of Science in Electrical Engineering." "Presented to the faculty of California Polytechnic State University, San Luis Obispo." Major professor: James Harris, Ph.D. Includes bibliographical references (leaves 70-72). Also available online and on microfiche (2 sheets).

Thesis (Ph.D.)--Electrical and Computer Engineering, Georgia Institute of Technology, 2008. / Committee Chair: Honsberg, Christiana; Committee Co-Chair: Citrin, David; Committee Member: Doolittle, Alan; Committee Member: First, Phillip; Committee Member: Ralph, Stephen; Committee Member: Rohatgi, Ajeet

Thesis (M.S.)--University of Nevada, Reno, 2008. / "December 5, 2008." Includes bibliographical references (leaf 55). Online version available on the World Wide Web.

Thesis (Ph. D.)--University of New South Wales, 1999. / Completed at: University of New South Walas, School of Electrical Engineering. Title from electronic deposit form.

Thesis (M. S.)--Electrical and Computer Engineering, Georgia Institute of Technology, 2009. / Committee Chair: Doolittle, W. Alan; Committee Member: Ferguson, Ian; Committee Member: Graham, Samuel; Committee Member: Rohatgi, Ajeet; Committee Member: Shen, Shyh-Chiang.

Thesis (M. Phil.)--University of Hong Kong, 2009. / Includes bibliographical references. Also available in print.

Thesis (M.S.)--Missouri University of Science and Technology, 2010. / Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed July 19, 2010) Includes bibliographical references (p. 88-90).

Prepared for the United States Dept. of Energy under Contract no. EX-76-A-01-2295, Task order 37.

The following report is conducted as a feasibility study, aimed to objectively uncover the advantages and challenges of increasing the amount of small scale solar power in Sri Lanka. The demand for electricity in Sri Lanka has been steadily increasing the last few years and there is an urgent need to find new ways of generating electricity. To not further increase the already high dependency of foreign oil and to decrease the impact on the environment, a transition from traditional combustion of fossil fuel to new renewable energy is required. The report shows that there exists substantial potential for generating solar energy in Sri Lanka. Calculations show that an investment in a photovoltaic system can be economically favourable and that the investment often is paid back within a few years. Current regulations and electricity pricing increases the economic incitement for high electricity consumers to invest in small scale solar power. Furthermore, the report demonstrates that there are likely no technical obstacles of increasing small scale solar power at this period. In contrary, the report shows that small scale solar power in general decreases line losses, voltage drops, and the peak demand of electricity. At present, it is probably not the lack of economic incitement but rather socio-economic factors that limit the development of small scale solar power. Sri Lanka is still a relatively poor country and the long years of civil war have prevented development and wealth. Lack of funds and a high ratio of low-income earners are probably the main reason for the slow development

Organic photovoltaic (OPV) is an exciting energy harvesting technique. Although its power conversion efficiency (PCE) now exceeds 10% in a research laboratory, the processing window of an OPV cell is still narrow. A fundamental understanding of the OPV materials is desired. This thesis presents the charge carrier transport properties and electronic interactions in the bulk heterojunction (BHJ) active layer of OPV cells. They were found to be well correlated with OPV device performances. Space-charge-limited current (SCLC) measurements and admittance spectroscopy (AS) were employed to study the charge transports, while photothermal deflection spectroscopy (PDS) was used to probe the trap densities inside the materials. Beneficial effects of a common solvent additive, 1,8-diiodooctance (DIO), on PTB7:PC71BM OPV cells have been investigated. With DIO present in the casting solution, the resulting BHJ films have much enhanced electron mobilities, whereas the impact on the hole mobility is negligible. The origin of increased electron mobility is the reduced average electron hopping distance for those films prepared with DIO solvent additive. A balance of hole-electron mobility by tuning the DIO concentration was demonstrated to be the way to optimize the OPV device performance. In light of carrier transport measurement results, a "polymer-rich" strategy with preserved device performance was demonstrated. After understanding the importance of balanced hole-electron mobility, the impact of donor-acceptor weight ratio on the performance of PTB7 : PC71BM based OPV cells was explored. Early stage electronic donor-acceptor interactions were revealed using ultra-low dosages of fullerenes. Before electron transport pathways percolate, the unconnected fullerene domains act as traps and hinder electron transport. From PDS, the trap density observed inside BHJ films was found to be anti-correlated with the fill factor of OPV devices. The origin of low FFs is mainly due to electron traps and localized states from fullerenes. Based on the observations, it is proposed that PC71BM tends to intercalate with PTB7 backbone instead of forming self-aggregates before the electron pathway percolation. Apart from investigating the fundamentals in OPV devices, a solution to improve its processing window was proposed in this thesis. Thermally stable polymer : fullerene OPV cells were fabricated by employing fluorenone-based solid additives. A charge transfer interaction between the additives and donor moiety of polymer formed a locked network which freezes the BHJ morphology under thermal stress. The most promising result retains 90% of the origin efficiency, upon thermal aging at 100 °C for more than 20 hours in PTB7:PC71BM solar cells. Besides fullerene-based OPV, all-polymer photovoltaic solar cells (all-PSCs) were also investigated. Two new difluorobenzene-naphthalene diimide based polymer electron acceptors, one random (P1) and one regioregular (P2) structure, were compared. P2 exhibited a much better molecular packing, a higher electron mobility and more balanced hole-electron mobilities in its composite film with polymer donor, PTB7-Th. An optimized PTB7-Th:P2 device can achieve a respectably high PCE over 5% for all-PSC devices. These all-PSCs should open a new avenue for next generation OPVs.