What is a polycrystalline solar panel?
Polycrystalline materials are materials made out of several crystals (rocks) of silicon.
All crystalline PV panels are made of silicon. Scientists say it is the second most abundant element on the earth crust. Silicon is obtained from rocks and at all times it is found in its combined state as silicon dioxide.
How polycrystalline panels are made?
The process of making a polycrystalline PV panel can be quite tasking.
It starts by first extracting silicon from the rock by means of a very hot furnace of over 2,000oC. The furnace melts the rock into liquid, and this is then poured into a cooling machine. The result of this cooling is a pure silicon rock which is ready for processes to become a PV panel.
Silicon in its pure state is just a semiconductor which does not conduct easily because of its atomic structure. A material conducts when it has free electrons or free holes, but pure silicon does not have any. However, this can be improved by adding impurities to this silicon. The process whereby impurities are added to a pure element is called doping and the added elements are called dopants.
The dopant and the silicon rocks are mixed in a 3 ft x 3 ft square-shaped mold and the mold is inserted to a large furnace of temperature of about 2500oF. The mold stays in the furnace for about 20 hours for a proper melting process. It is removed after this period and allowed to cool for a day or two.
After the cooling a solid silicon block (ingot) is obtained. This ingot is sliced into a thin and fragile square shaped solid called wafer.
There are two stages when it comes to cutting an ingot; the first stage is where the entire solid is cut into a column of the required size but a very long width and the second stage is where the width is removed by cutting the column into the desired thin sheets -the wafer.
Though we’ve obtained the wafer the process is yet incomplete, unless the thin sheets are carefully collected and separated for the cleaning process.
Due to the fragility of these solids, hands are used to separate the solids individually and since hands are involved our material becomes more prone to contamination, because of this the wafers are washed properly after the collection.
Lastly is the addition of the last chemical unto the already washed wafers, this is then baked to obtain a fusion of the two materials.
Other finishing touches will be; addition of anti-reflective clothing on the panel, addition of chemicals to help the panel to better conduct electricity out of the panel, addition of aesthetic value to make it more visually appealing and addition of electrical contacts to help convey out the converted electricity.
