الفهرس 
Literature SurveyOnly 14 pages are availabe for public view
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Abstract
This research work aims to develop an economical solar cell utilizing nano-materials via the spin coating technique. The proposed cell is cheaper to fabricate than Silicon based solar cells. The proposed Quantum Dot Solar Cell has massive potential in reducing the cost of cells production as well as improving the solar cell efficiency.
In this research work the proposed solar cell can be explained as a sandwich structure formed of different layers of different materials each of them has a specific function. Those layers of materials are deposited on a conductive glass substrate the material used is Indium Tin Oxide (ITO). The first type of material deposited is TiO2 and the number of layers of TiO2 is constant at 3 layers. The material deposited after on top of the TiO2 is Cadmium Selenide CdSe, this material will be the topic of study. The number of CdSe layers are varied from 1, 3, 20, 50, 100 and 500 layers deposited to understand the impact on efficiency. Before sealing the cell Iodide is added and acts as an electrolyte. The back electrode is Carbon soot deposited on ITO glass. Brafin is used to seal the solar cell.
There are 3 designs blocks in this research and each block has different cells. Block one is the solar cell formed by CdSe layers deposited on TiO2. Block two is replacing the CdSe material by surface modified CdSe material and for the third block we add Graphene to the Cell of Block 2.
The first step of the research was to explore the best number of CdSe layers. The best number of layers was found to be a hundred layers of CdSe. The next step was to deposit 100 layers of Surface Modified CdSe following the similar cell structure. Then when for block 3 the CdSe was replaced by 100 layers of Surface Modified CdSe Graphene.
In this research a total of 8 solar cells have been fabricated and are explained in detail in this thesis.
In this study, Chapter 1 “LITRATURE SURVEY” introduces the world energy challenge, the explanation and background for the Photovoltaic principle, the physics behind the photovoltaic solar cells, the anatomy of the solar cells, as well as the different generations of the solar cells. The key take away is that the world demand for energy is always increasing; currently the percent of supply generated from solar cell is negligible. The biggest challenge is the high cost of solar cells in the market which is mainly Mono-crystalline or Poly-crystalline Silicon solar cells. This chapter illustrates how Nano-materials can improve the efficiency of solar cells due to their tunable band gaps, explains quantum dots, Graphene and Plasmonic. Chapter 1 also includes a brief on different solar cell fabrication techniques.
Chapter 2 “PROBLEM DEFINITION AND PLAN OF WORK” presents the motive for this thesis based on previous researches showing the promising future for Dye Synthetized Solar Cells as well as Quantum Dot Dye Synthetized Solar Cells (QDDSSC). The first portion of this Chapter explores the different techniques that could be utilized to fabricate the Thin Film QDDSSC. The second portion explores previous techniques used and what were the results and to identify which would be the best technique to follow and improve on in this thesis. Chapter closes with the plan of work specifying the steps to be followed to fabricate the solar cells, different variants and the characterization techniques.
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Chapter 3 “EXPERIMENTAL TECHNIQUES AND PROCEDURES” presents the material selection process. Explores why Nano-Titanium Dioxide has been picked as the first material as it has a large band gap, Cadmium Selenide Quantum Dots picked as the light absorbing material as it has smaller band gap and explains why graphene could enhance the solar cell efficiency if added to the Cadmium Selenide Quantum Dots. The second part of this chapter explains the instrumentation used in characterizing and testing the solar cell properties as well as the absorption and structure of the nano-materials fabricated. The third part of this chapter shows the characterization of TiO2, CdSe and CdSe Graphene. Those materials are characterized by Transmission Electron Microscope to understand their nano-structure. The absorption of those materials is presented in this section as well. The chapter presents the experimental work in the following sequence: material fabrication steps, followed by structure characterization for the material, followed by the optical characterization of this material. The final section of this chapter explains the steps of fabrication of the solar cell.
Chapter 4 “CHARACTERIZATION OF THE SOLAR CELLS)” presents the detailed results of each solar cell fabricated this included; each solar cell Open Circuit Voltage, Short Circuit Current and Maximum Power is represented as well as each cell’s Current-Voltage Curve (I-V Curve) is presented. The efficiency of each solar cell is calculated and shown in this chapter as well.
Chapter 5 “RESULTS AND DISCUSSION (PHASE IDENTIFICATION)” presents the summary of results of the solar cells and compares all fabricated solar cells’ properties to each other. This includes identifying the impact of the increased number of layers of Cadmium Selenide on the Current, Voltage, Power, Fill Factor and Efficiency of the solar cell.
Chapter 6 “Conclusions” shows the results of the experiments and derived conclusions and discussion of the results. The three major conclusions are first, 100 layers of Cadmium Selenide deposited on the Titanium Dioxide resulted in the highest solar cell efficiency of this block (Only Cadmium Selenide). Second, Replacing Cadmium Selenide by Surface Modified Cadmium Selenide has reduced the solar cell efficiency. Third, Graphene improves the efficiency of SM Cadmium Selenide.
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Introduction
Previous work revealed that the world demand of energy is growing exponentially, we have used 4.1 X 1020 joules per year 2007 (13 Trillion Watt) with the evolution of technology the demand for energy is expected to go up to 50 trillion watts by 2050, with this increase in demands our fossil fuels can’t meet the demands and with the triple consumption of those fuels the pollution would increase. Reverting to green energy is inevitable. The sun generates 120,000 TW of radiation. If we would cover only 0.16% of earth’s land with solar cells at 10% efficiency this systems would provide 20 TW of power, almost double of the world’s consumption rate of fossil energy. (Lewis, 2005) [1]
Finding alternative clean sources of energy has been a global challenge for decades, the world still depends on fossil fuels for the majority of it energy demands. Fossil fuels have a direct correlation to the carbon dioxide levels observed which has harmful effects on the environment and causes many concerns in example climate changes.
One of those renewable clean energy sources in the sun. Solar energy is abundant and only covering 0.08% of earth’s area could cover the world’s energy demands. However, most solar cells that harness the solar energy are either very expensive or inefficient.
The purpose of the present research work is to develop new solar cell based on economical deposition techniques as well as cheaper nono-materials. The deposition technique to be followed would be spin coating of the materials in a layer over layer deposition technique. The proposed materials to be used will be TiO2, CdSe and Graphene.
TiO2 be constant in all experiments at 3 layers deposited via spin coating on the conductive glass substrate (ITO), then layers of CdSe will deposited on that layer of TiO2 and then will be enhanced by Graphene.
The objective