Date of Award

8-25-2011

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Applied Science

First Advisor

Alexandru Biris

Abstract

As the human race evolves and continues to progress in the future, we will face some obstacles during the advancement. Challenges like water, food, and poverty crisis, pollution, population explosion, and diseases are impediments in the development of mankind. Above all, with the development arises the need to fulfill the energy requirements. There are number of technologies available to answer the present energy needs, e.g. coal, nuclear, oil/natural gas, hydropower, etc. All these technologies have their advantages and disadvantages, with disadvantages being greenhouse gas emissions and other environmental impacts. One technology which has lagged behind due to high cost is photovoltaics (solar cells). Everyday enough sunlight energy reaches Earth's surface which can fulfill all our energy needs for one year. With proper technological development, solar power can become a major source for energy generation. The problem lies in the price of energy, which is far higher when produced with solar cells and compared with other means of energy generation techniques. The high energy cost in solar cells is due to complex fabrication techniques which raises the cost of solar devices. In this work novel organic materials have been studied which are easy to process and can help in fabricating cheap solar cells. A few of these materials are poly(3-hexylthiophene) (P3HT), carbon nanotubes, graphene, etc. Although there has been research performed in the past on the application of these materials in solar cells, the underlying role that these materials play in photovoltaic devices is still poorly understood. In this work P3HT-multi-wall carbon nanotubes nanocomposites, P3HT-graphene composites have been synthesized and their structural, thermal, optical, and electrical properties have been studied. This work also includes a relatively new design of hybrid solar cells which utilize the hole accepting nature of doped carbon nanotubes in n-silicon based devices. Work has been performed on similar devices employing silicon substrates with varying resistivities, which has been found to have dramatic effect on the device performance. Another new type of hybrid solar cell has been studied and is based on layered heterojunctions between polyaniline (PANI), single-wall carbon nanotubes, and n-type silicon.

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