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Silicon – Important Raw Material in Solar Energy

Silicon – Important Raw Material in Solar Energy

Which raw material is essential for solar modules and the conversion of sunlight into electricity? We take a look at the production and value chain of solar modules.

In principle, several materials can be used to manufacture solar cells. However, 95 percent of all solar cells are made of the semiconductor material silicon (Si).

Semiconductors are substances that become electrically conductive when exposed to light or heat, while they have an insulating effect at low temperatures. Whether in smartphones, cars, game consoles or solar modules – semiconductors are used in many areas.

From sand to finished module

The good thing about silicon as a semiconductor material? The raw material silicon is - literally - a dime a dozen. After oxygen, silicon is one of the most abundant elements on earth and is actually contained in sand and quartz. However, the quartz sand from which the silicon needed for solar cells is extracted is not taken from beaches but is usually extracted from mines. Mining is very energy-intensive and is therefore usually carried out in countries with low energy costs.

PV Value Chain -  Solar module

Silicon, as it occurs in nature, however, is not directly suitable for solar cells. In order to produce silicon that is suitable for semiconductors from raw silicon, the silicon must have only a low level of contamination by foreign atoms - to be more precise, the silicon must be 99.99 percent pure. This means that there must be significantly less than a single foreign atom per billion silicon parts. This high degree of purity is achieved by a multi-stage purification process and is important for the rest of the process.

The purified silicon is now processed into ingots. Ingots can be monocrystalline or polycrystalline. In the case of polycrystalline ingots, the purified silicon is melted down and cast into a cuboid mold. In this process, the silicon acquires its typical amorphous lattice structure during curing. The production of monocrystalline ingots, on the other hand, is somewhat more complex and is carried out by dipping a so-called seed crystal into a melt of the semiconductor material. By slow controlled lifting under rotation (so-called pulling) it obtains the characteristically shaped round columns.

The ingots are then cut with special wire saws or waterjet cutting into silicon wafers about 200 micrometers (0.2 millimeters) thick, which are now ready for further processing into solar cells. When silicon wafers are sawn, almost half of the material is lost in the form of sawdust. Around 5000 200-millimeter wafers can be produced from one ton of sand. Wafers are the physical basis of the solar cell - their quality thus has a decisive influence on its quality.

A solar cell is made up of two layers with different charges. To ensure that the positive and negative charge carriers are properly conducted, foreign atoms are incorporated into the semiconductor. This is known as p-doped and n-doped silicon. The cell is then usually coated with a bluish shimmering anti-reflective layer to protect the cell from environmental influences and reduce light reflections. The metal contacts are then applied to the front and rear sides. The next production step is the lamination of the module. In a vacuum or at high heat, the cells are permanently laminated between a foil and the glass. The soldering of copper ribbons then makes it possible to connect several solar cells in series. After lamination, the edges are hemmed, the junction box is set and fitted with the free-wheeling diodes. An aluminum frame ensures the stability of the module.

Structure of a Solar Cell

Source: Solaranlage.de | emedien.design.hs-anhalt.de

 

Fun Fact

The name "Silicon Valley", the famous research and industrial complex on the U.S. West Coast, where more than a thousand IT companies are at work, comes from the world Silicon. There are many founding myths. Physicist William Shockley is considered as the unofficial father of "Silicon Valley”. He founded a silicon semiconductor factory near Palo Alto in 1956. The garage where Bill Hewlett and Dave Packard laid the foundation for the Hewlett-Packard (HP) success story is still there today.

 

Solar Modules at Krannich

In our Krannich Online Shop you will find a variety of different modules, which are subject to strict quality controls to guarantee high efficiency. Our product portfolio includes crystalline and optimized modules, as well as glass-glass modules. Have a look!

 

25.06.2021 08:00
by Eurem Krannich Team

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