Solar cells are made by treating thin silicon wafers with chemicals to enable them to produce an electrical charge when exposed to sunlight. The process involves several key steps:
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Silicon Wafer Preparation: Thin wafers of silicon, a semiconductor material, are the foundation of most solar cells. High-purity silicon is crucial for efficient energy conversion.
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Doping: The silicon wafers are "doped" with other elements to create an electrical imbalance. Typically, one layer is doped with phosphorus (n-type), which adds extra electrons, and another layer is doped with boron (p-type), which creates "holes" (a lack of electrons). This creates a p-n junction, which is essential for solar cell function.
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Anti-Reflection Coating: A thin anti-reflective coating, often made of silicon nitride, is applied to the top surface of the silicon wafer. This coating minimizes light reflection, allowing more sunlight to enter the cell and generate electricity.
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Metallization: Metal contacts are added to both the top and bottom surfaces of the solar cell. These contacts act as electrodes, collecting the electrical current generated by the cell and channeling it into an external circuit. The top contact is often in a grid pattern to allow sunlight to pass through.
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Cell Interconnection: The individual solar cells are then connected in series to form a "string." The number of cells in a string depends on the desired voltage output.
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Encapsulation: The cell strings are then encapsulated between layers of protective materials, typically ethylene-vinyl acetate (EVA) plastic and glass. The EVA plastic acts as an adhesive and sealant, protecting the cells from moisture and other environmental factors. The glass provides mechanical support and further protection.
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Lamination: The layers (glass, EVA, cell strings, EVA, backsheet) are then heated and laminated under vacuum to create a watertight and durable module.
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Framing and Junction Box: Finally, the laminated module is framed with aluminum for structural support and ease of installation. A junction box containing wiring and connectors is attached to the back of the module, allowing it to be connected to an electrical system.
In summary, solar cell manufacturing involves sophisticated chemical and physical processes to transform raw materials into devices that efficiently convert sunlight into electricity.
