Silicon wafers are actually the primitive form of solar cells, and the manufacturing process of silicon wafers is not complicated. The first step is to manufacture silicon ingots, which requires the use of crucibles. Crucibles, also known as mineral arc furnaces or electric arc furnaces, are usually made of graphite with a diameter of 12 meters. There are also two three meter long graphite electrodes in the middle for heating. Graphite is related to diamond and is an allotrope of carbon. Isotropes are elemental forms with the same elements but different arrangements, forming different properties. Simply put, eggs can be boiled or fried. The melting point of graphite is as high as 3800 ℃, but its expansion coefficient is very small. Therefore, graphite crucibles have become the most ideal smelting equipment.

First, about 60 tons of silica is placed in a crucible, followed by about 25 tons of coal and sawdust. Under the high temperature of 2000 degrees Celsius, the silica gradually melts and undergoes a reduction reaction with carbon. The main reaction is that silica reacts with carbon to form elemental silicon and carbon monoxide, while the secondary reaction occurs at a lower temperature inside the furnace to form silicon carbide. The smelted silicon is condensed to obtain relatively pure silicon ingots, which are smelting grade industrial silicon with a purity of about 98% -99%, but still contain a small amount of impurities such as iron and aluminum.  

The second step is the purification of industrial silicon, and the mainstream method is to use hydrogen chloride gas for purification. The specific operation is to crush the silicon ingot into slag. At a high temperature of 325 degrees, the silicon slag will react with hydrogen chloride to produce hydrogen gas and trichlorosilane, as well as impurities such as ferric chloride, aluminum chloride, and silicon tetrachloride. By using the different boiling points of these gases, the temperature is controlled through a condenser and distillation tower to separate the trichlorosilane gas with a lower boiling point. Then, high-purity trichlorosilane is reduced to solid silicon. The method is to introduce hydrogen gas into the high temperature environment at 1100 ℃ to produce silicon, hydrogen chloride, and silicon tetrachloride. At a temperature of 1100 ℃, only silicon is solid, so we will see black color in the reaction furnace. The silicon rod slowly grows out and can accumulate about 250 kilograms of silicon rod in about a week, The silicon content can reach up to 99.99999999%.