We are all aware of the term solar panels. Right?
Today, let’s have a discussion on how solar panels are made.
What’s the science involved behind building this eco-friendly innovation?
Solar energy is important for our futures. It is one of the most important sources of renewable energy and the cheapest too.
The total solar energy absorbed by Earth’s atmosphere, oceans and landmasses are approximately 3,850,000 exajoules (EJ) per year. In 2002, this was more energy produced by the sun in one hour than the world used in one year.
The amount of solar energy reaching Earth is so much that in just one year, it is twice as much as we will ever be able to get from all of the Earth’s non-renewable resources of coal, oil, natural gas, and uranium combined.
This all sounds very impressive but it leaves many people thinking of how these solar panels are so inexpensive, while still providing green energy.
The answer to this question lies in how these solar panels are made. But before we get into how the panels are manufactured we need to know what makes up a solar panel. Let’s go step by step.
What Are Solar Panels Made Of?
A solar panel is comprised of different layers which consist of different elements.
Solar photovoltaics (PV) are made with several parts, the most important of which are silicon cells.
Silicon is hard and brittle. It is the second most abundant element on the Earth and it naturally converts sunlight into electricity.
When the light comes in contact with a silicon cell, it sets the electrons to be in motion which starts a flow of electricity. This is called the “photovoltaic effect.”
Check out this article if you want to know more about the photovoltaic effect and how solar panels work.
Stages For How Solar Panels Are Made
There are a lot of stages involved in making a solar panel, seven to be exact. Also, these stages are filled with a lot of technical aspects involved in the explanation but we tried to keep it simple.
Stage One: Getting the silicon
The very first step involved in making these solar panels is getting the silicon in the purest form by removing its impurities.
The silicon dioxide is placed into an electric furnace. Next, a carbon arc is applied in order to release the oxygen. This results in carbon dioxide and molten silicon.
This will yield silicon that only has 1% impurity but it is not yet pure enough for solar cells.
The silicon which is currently at 99% purity, is purified even further using something called the floating zone technique.
A rod of impure silicon is passed through a heated zone many times in the same direction which helps in dragging the impurities towards one end.
After doing it enough times the silicon is said to be pure and the impurities at one end are taken out.
Stage Two: Making single crystal silicon
Once we have separated the purest silicon, then the next step is to make a single crystal of silicon.
Solar cells are made from silicon boules, which are polycrystalline structures that have the atomic structure of a single crystal.
The most commonly used method for the creation of the boule is known as the Czochralski method. During this process, a seed crystal of silicon is put into melted polycrystalline silicon.
As the seed crystal is withdrawn, it is rotated, which means a cylindrical ingot, which is the boule, of silicon, is formed. The ingot is completely pure, as all impurities are left in the liquid.
Stage Three: Making silicon wafers
A Silicon Wafer
Silicon wafers from the boule are cut using a saw, the inner diameter of which cuts into the rod.
A diamond saw is best for cutting, producing a cut that is as wide as the wafer.
Around one-half of the silicon is lost from the boule to the finished circular wafer. More can be lost if the wafer is cut into a rectangular or hexagonal shape.
These shapes are sometimes used in solar cells because they can be fit together perfectly, making use of all the space on the surface of the solar cell.
Next, the wafers are polished to remove any marks but some manufacturers leave these marks as they believe that these cells may absorb the light better.
Stage Four: Doping
The most recent way of doping silicon is with phosphorous using a small particle accelerator to shoot the phosphorous ions into the ingot.
By controlling the speed of the ions, it becomes possible to control the depth of penetration.
However, this new process has not yet been fully accepted. The traditional method tends to involve the introduction of a small amount of boron during the previous stage.
Stage Five: Placing electrical contacts
Electrical contacts are used to connect one solar cell to the other as well as to the receiver of the produced current.
The contact needs to be very thin so that they do not block any sunlight from being harnessed by the cell.
Metals like palladium or copper are vacuum evaporated through a photoresistor deposited on the exposed portion of cells that have been partially covered with wax.
After the contacts have been put in place, thin strips are placed between the cells. The most commonly used strips are tin-coated copper.
Stage Six: The anti-reflective coating
Pure silicon is very shiny, which allows it to reflect up to 35 per cent of the sunlight it is hit with.
To reduce the amount of sunlight that is lost, an anti-reflective coating is put onto the silicon wafer. The most commonly used types of coating are titanium dioxide and silicon oxide.
The material used for the coating is either heated until its molecules boil off and travel to the silicon in order to condense or the material undergoes sputtering.
During this process, a high voltage will knock molecules off the material and deposit them onto the silicon and then deposit them onto the silicon at the opposite electrode.
Stage Seven: Encapsulating the cell
The finished solar cells are then encapsulated.
Which means that they are sealed into silicon rubber or ethylene-vinyl acetate.
The encapsulated solar cells are then put into an aluminium frame that has a back-sheet and a glass or plastic cover.
We hope you got an idea about the deep technical details involved in making a solar panel. We tried to keep it simple still but if there is something you found difficult to understand do reply we will help you out with everything.
GO GREEN. SWITCH TO SOLAR.