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Solar Cells

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Sabiyah Siddiqui

on 3 June 2013

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Transcript of Solar Cells

An Introduction to Solar Cells A New Kind of Energy Sources Basic component is pure silicon which is not pure at its natural state.The raw materials are silicon dioxide of quartzite gravel or crushed quartz - placed into an electric arc furnace.Carbon arc applied to release the oxygen. Results in carbon dioxide and molten silicon. Silicon still needs further purification. The resulting pure silicon is treated with phosphorous and boron to produce an immense amount of electrons and a deficiency of electrons appropriate to make a semiconductor able to conduct electricity. Materials Conversion of Light Into Electricity Photovoltaic Effect Recombination will take place in electrical wires (external circuit) - this causes a current to flow (a photo current). Photo conductors react to light by changing their electric conductivity. Need battery to draw current.

If electric field is put into semiconductor, electrons and holes will separate.
Part with electrons - negative
Part with holes - positive
Electrodes provided at both sides, current can flow between them. When crystal is exposed to sunlight it acts as battery and becomes a solar cell. http://www.chemistryexplained.com/Ru-Sp/Solar-Cells.html




http://greenliving.nationalgeographic.com/introduction-solar-panels-2347.html Introduction Solar Cells: Helping the World Live Longer The use of solar cells preserve a tremendous amount of nonrenewable resources and fossil fuels. This technology can replace fuel for transportation, can power houses and all appliances within them, and provide a cleaner environment for many people in today's cities and towns. Research into solar electricity followed quickly after research of overall electricity. What are Solar Cells Solar cells are basic and simple semiconductors that work to convert light into electricity. It is a proficient way to preserve nonrenewable resources Discovering Other Uses For Our Sun 1839 - Antoine-Cesar Becqueral exposed a chemical battery to the sun to see it produce voltage. First conversion of sunlight into electricity was 1% efficient A thermonuclear process that converts about 650,000,000 tons of hydrogen to helium every second created the sun's energy. Electromagnetic radiation stream out from sun into space in all directions. Only a small fraction of the radiation produced reaches Earth. This small portion is more than enough to power solar panels and allow them to produce electricity 1873 - Willoughby Smith discovered selenium was sensitive to light. 1877 - W.G. Adams & R.E. Day found that selenium produced an electrical current when exposed to light. 1880 - Charles Fritts used gold coated selenium to make first solar cell - only one percent efficiency. Different Forms Because silicon disks are shiny, they require an anti-reflective coating that usually is titanium dioxide. Solar Module: silicon semiconductor surrounded by protective material in a metal frame.
Protective Material: incapsulant of transparent silicon rubber bonded around the cells.
Put in ethylene vinyl acetate. Polyester film makes up the backing. Glass cover on terrestrial arrays, lightweight plastic covers on satellite array. Electronic parts mostly consist of copper, frame either steel or aluminum, silicon used as cement to put and hold together. Power Measurement Electricity measured in watts - one thousand watts in kilowatt - one thousand watts in one hour=kilowatt-hour (kWh) Solar Panels -- kWh=amount of energy produced by the panel. It is the creation of voltage or electrical current in a material with exposure to sunlight. Valence electrons absorb energy when sunlight, or any light is present on its material. This results in the excitement of the electrons, causing them to jump to the conduction band and become free. These electrons are now non-thermal and greatly excited- they diffuse. Some of them reach a junction and are made into a different material. This action forms an electromotive force and so some of the light energy is converted to electrial energy. Completed by absorbing light and ionizing crystal atoms This forms free negatively charged electrons and positively charged ions. The ionized state are readily able to move from one neighbor to another by exchanging ions. This is now mobile. It behaves like an electron and called a hole. Similar to free electrons except with a positive charge. Each photon of light will set free an electron hole pair to move through the lattice in random formation, only if the photon has a high enough energy to be absorbed by the crystal's atoms. Will never move too far away from each other. Coming too close will cause them to recombine. A separation between the electron and hole pair will occur when they experience an electric field (a region around a charged particle where which a force would be exerted on the other charged particles or objects). At this time the electrons will drift towards the positive pole and the positively charged ions to the negative.
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