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SINGLE CRYSTAL SILICON PV CELLS www.solarcell.net PARTS OF A SOLAR CELL Electrically conductive grid on top surface to carry electrons 1-2 layers of anti-reflective coating to increase absorption The collector: a thin layer of silicon An electrode in contact with base layer to complete the circuit. SILICON Silicon is the most popular PV material Most cells are made from left over computer chip manufacturing Silicon must be refined to almost 100% purity The uniform molecular structure of silicon makes it efficient for electron transport Silicon wafers are cut from ingots CZOCHRALSKI PROCESS This is the process of creating an ingot. A small single silicon rod (seed) is placed in an inert gas at high temps. When the seed is rotated up and out silicon adheres to it to form an ingot. CELLS -> MODULES Wafers 5 inches square and .012 inches thick are sliced from the ingot. They are then processed into cells and soldered together to achieve the desired voltage. Cells arrayed in series are called modules. TWO TYPES OF CELLS There are two types of single crystal silicon cells: n-type or p-type TECHNOLOGY PV cells exhibit voltage or current when exposed to light. The light liberates electrons which move through the cell creating current. The larger area there is the more current. Single crystal silicon cells are the most efficient at 15-24% sunlight-to-electricity conversion rate. They are also the most expensive to produce at $6.50/ watt. MANUFACTURERS Sharp Electronics Corporation Sanyo bp Solar Shell Sunwise Uni-Solar AstroPower PRICE COMPARISONS Shell: 80 watt panel 47.2”x20.8”x1.3” $328.00 • Sunwise: 85 watt panel 56.89”x22.83” $351.00 AstroPower: 75 watts 47.2”x20.7”x1.4” $325.00 BIBLIOGRAPHY “Photovoltaic Materials-Silicon”. www.azom.com/details.asp?ArticleID=1169 SOLARTROPE Supply Corporation. 2002. www.solartrope.com. Resource Center Technologies. G/rated. www.green-rated.org/resctr_tech.asp?id=1 www.physics.pomona.edu/COURSES/phys17/papers/PV.pdf www.mrsolar.com www.oksolar.com