Silicon Based PV Cells

* The battery applies a voltage to the plates, charging one plate positive and the other plate negative. Alpha particles constantly released by the americium knock electrons off of the atoms in the air, ionizing the oxygen and nitrogen atoms in the chamber. The positively-charged oxygen and nitrogen atoms are attracted to the negative plate and the electrons are attracted to the

Why do electrons (blue dots) move? Draw a diagram of the battery, label the flow of electrons. The flow of current (+) is opposite; draw this and note if toward or away from + terminal of the battery.

c) How the Band Theory predicts that the conductivity of silicon increases as the temperature increases.

The greatest energy that can be produced by the sun is electricity. Photovoltaics, or solar cells, capture the sun and convert it into electricity. Solar cells were discovered by the Europeans back in the 1870’s when they used selenium to develop the telegraph. They found that when light hits selenium it would produce and electrical current. Soon enough there were many scientists and engineers working on photovoltaic systems. Silicon and Selenium proved to be the two best elements to conduct electricity when light hits them. Photovoltaic systems (PV cell) work by converting the suns light into electricity. A semi conducting material absorbs the sunlight, that energy knocks electrons loose from their atoms, this allows the electrons to flow through the material to produce electricity. The further development of solar cells can be attributed to the satellite industry. Solar cells were expensive and there was no use for them until satellites came. Because it is impractical to tether satellites it became important to develop solar energy at any cost that would power these satellites. This created a sustainable market for solar power, the first of its kind.

Deposition and characterization of the thin films discussed in Chapter 1 will require an understanding of many different tools and processes that are currently used in the semiconductor industry today. This chapter will cover the principles behind the growth process, the experimentation and the material properties. The equipment used for these processes will be discussed in depth as well.

PV cell works on the principle of photoelectric current. When the light strikes the surface of a semiconductor material, some of the energy is absorbed by semiconductor material

Silicon single-electron transistors (Si SETS), fabricated by pattern-dependent oxidation in Si wires, exhibit conductance oscillations at a temperature as high as 300 K which corresponds to a charging energy of approximately 30 meV .A recent experiment has revealed interesting characteristics of such small Si SETS at high temperatures. For temperatures above 10 K, the conductance peaks G peak increase rapidly with increasing temperature T, showing a thermal activated behavior G peak = exp(-U/T)with activation energy U over potential barriers that localize electrons in the quantum dot..

As the world is suffering from an ever diminishing stock of fossil fuels and serious pollution being caused by fuels, solar energy has become the most promising solution to the global energy crisis. Among various methods for generating energy from the sun, solar cells are an effective approach for converting solar energy into electrical energy for regular use. There is a wide range of research activities around the world that has demonstrated the efficiency potential of crystalline silicon cells. Most of the research studies has inferred, both theoretically and practically, that thin crystalline silicon cells can have low manufacturing costs while not compromising on reasonable efficiencies. Many researchers have attempted to study the impact of wafer thickness on the performance of crystalline silicon cells, and the best efficiencies on wafers with thickness under 200µm are typically in the range

silicon. The electrons will then flow towards the positive side of the solar cells instead of in

Solar photovoltaic cells are catogorized into three generational groups. First generation cells are made from crystalline silicon, expensive to construct, and offer little flexibility. Second generation cells are made from amorphous (non-crystalline) silicon, cheaper to make than crystalline, offer some flexibility, yet still utilize rare and often toxic materials. Consequently, the maturation of the build process for 1st and 2nd generation

We have now discussed the two extremes in electronic materials; a conductor, and an insulator we will now move to a material that lies in between these two, a semiconductor. The

Solar photovoltaic (PV): The transmutation of sunlight directly into electricity by using photovoltaic cells. Photovoltaic systems can be lodge on rooftops, integrated at the top of building designs and vehicles, or scaled up to megawatt scale power plants.

hotovoltaic(PV) technology is booming, with the pursuit of sustainable energy is continuously increasing in rate of over 30% per year since 1999 [1]. At present, the most commonly PV technology is crystalline silicon cells. This is powerful and stable PV technology. However, its potential of cost reduction is strongly limited, with the high cost with silicon wafer. Recently thin-film solar cells as a substitute for traditional crystalline silicon cells, it has up to 21.5 percent of the photoelectric conversion efficiency, while its production cost is only one-third of the crystalline silicon cells or even one-third [2].

The conversion of the sunlight directly into electricity by using the electronic properties of various suitable materials appears to be an attractive energy conversion process and more or less an ideal alternative to available conventional energy sources. The solar cell technology has developed enormously over the last four decades, initially for being used to provide electrical power for spacecrafts and also more recently for various terrestrial applications. The main reason for this technological development lies in the realization that traditional fossil energy resources like coal, oil and gas are not just rapidly depleting, but they also contribute to unpredictable and probably irreversible climate changes in the approaching future through the extreme high emission levels of greenhouse gases (e.g. CO2, CO, SO2 and P2O5) and also due to acidification. The photo voltaic source of energy that is solar irradiation, has the major advantage of being widely distributed over the world. The solar irradiation falling on the earth’s surface is not a limiting factor and also supersedes our needs by far. Photovoltaic industry has leapfrogged the barriers over the last three decades from merely being a conceptual industry to a full-fledged commercial industry. Recent major investments and the on hand manufacturing facilities are only mainly for silicon based technologies, with more than 93% market share, mainly due to its maturity, growth and huge

Solar cells are also known as photovoltaic cells, which suggest that light energy is being converted to electrical energy. Most photovoltaic cells consist of silicon in its crystalline structure. In that structure, each silicon atom has four valence electrons, and each one bonds to an adjacent electron. Silicon then is a poor conductor since electrons cannot move freely through the substance, but the addition of impurities such as phosphorus, which is called doping, to the silicon crystalline structure provide extra electrons called free carriers that can be knocked off the atom via light energy.6 The section of the photovoltaic cell that is doped with phosphorus is called the N-type because it has numerous negatively charged electrons flowing and creating a current. On the other hand, the section of the photovoltaic cell that is doped with boron is called the P-type because boron only has three valence electrons.7 When the N-type and