There are three types of solar panels: monocrystalline, polycrystalline, and thin film.
The main difference between the solar panels types is the way in which the semiconductor material is made.
In this article, we will go through the different types of solar panels and what they are made of.
Monocrystalline Solar Panels
Monocrystalline silicon solar panels are made out of a single, large crystal of silicon. These types of solar panels are very efficient and have a long lifespan. However, they are also the most expensive.
How are Monocrystalline Solar Panels made?
Step 1: Make Metallurgical Silicon
The primary component in monocrystalline solar panels is silica, known as Silica sand, Quartzite, or SiO2.
Manufacturing monocrystalline cells begin with metallurgical silicon extraction from quartzite.
To create metallurgical (or “matt”) silicon, high-temperature ovens are used to melt SiO2 and Carbon at temperatures of over 2,552 degrees Fahrenheit, resulting in 98% to 99% pure silicon.
Although metallurgical silicon is highly pure, it isn’t sufficiently pure to be used in PV panels, so we need to further purify it.
Step 2: Purify the Metallurgical Silicon
This is often done using the Siemens process. Silicon is heated until it becomes a gas. Then, it is passed through an electrical arc where it recondenses into an extremely pure form of silicon known as monocrystalline silicon.
The Siemens process can purify silicon to over 99.9999% purity.
Step 3: Create Silicon Ingots
Now that the silicon is purified, it needs to be made into a monocrystalline ingot.
This is done using the Czochralski method.
We start by taking a small seed crystal of monocrystalline silicon and dipping it into a molten pool of metallurgical-grade silicon.
The seed crystal is slowly pulled out of the molten silicon, and as it does, more silicon from the pool attaches to it.
This process continues until a large monocrystalline ingot is formed.
Step 4: Cut the Ingots Into Wafers
Once the silicon ingots are made, they need to be cut into thin silicon wafers.
This is done with a diamond saw, and the resulting wafers are usually about 1 mm or 0.0393 inches.
After the wafers are cut, they go through a process known as chemical-mechanical planarization (CMP), which polishes the surface of the wafer to prepare it for the next step.
Step 5: Create Solar Cells
Solar cells are made of multiple layers of silicon, and each layer has a different task.
The first layer is the P-type silicon, which has been doped with boron. The next layer is the N-type silicon, which has been doped with phosphorus. These two layers are where the electrical current is generated.
The last layer is the antireflective coating, which helps to increase the amount of light that is absorbed by the solar cell.
Step 6: Assemble the Solar Cells Into a Panel
The final step is to assemble the solar cells into a panel. This is done by connecting the negative terminal of one cell to the positive terminal of the next cell, and so on.
The solar cells are then placed in a metal frame and covered with a glass or polymer sheet. Most solar panels are made up of 32 to 96 cells assembled in rows and columns.
Polycrystalline Solar Panels
Unlike mono solar panels, polycrystalline solar panels are made out of multiple silicon fragments instead of a single pure crystal.
While this makes them slightly less efficient than mono solar cells, they are cheaper to produce and require less processing.
How Polycrystalline Solar Panels Are Made?
The manufacturing process for polycrystalline solar panels is similar to that of monocrystalline solar panels with a few key differences.
The process of extracting and purifying the silicon is the same, however, instead of creating a single large ingot using the Czochralski method, the molten silicon is left to cool and solidify on its own.
This results in multiple small silicon fragments instead of one large one.
These silicon crystals are then melted in special ovens and poured into cubic-shaped molds. Once they solidify, the silicon blocks are cut into thin wafers, treated, and assembled just like mono solar panels.
Thin Film Solar Panels
Thin film solar panels are made out of a variety of materials including cadmium telluride (CdTe), copper indium gallium selenide (CIGS), and amorphous silicon (a-Si).
They are less efficient than mono and polycrystalline solar panels, however, they are much cheaper to produce. They are also more flexible and can be made into a variety of shapes and sizes.
How Thin Film Solar Panels Are Made?
The manufacturing process for thin film solar panels is different from that of mono and polycrystalline solar panels.
Once the semiconductor material is deposited, a top conductive layer and an electrical contact layer are added.
The final step is to connect the electrical contacts to the metal grid on the back of the solar panel.
Thin film solar panels are made in a continuous process, and the solar cells are cut from the substrate after they are made. This makes thin film solar panels cheaper to produce than mono and polycrystalline solar panels.
What is the back of a solar panel made out of?
The back of a solar panel is typically made out of metal, plastic, or glass. This is where the electrical contacts are located.
The metal grid is also located in the back, where it helps support the solar panel and also conducts electricity.
Are panels environmentally friendly to make?
Most solar panels are made out of silicon, which is a natural element that can be found in sand, which is an environmentally friendly material.
However, the process of extracting and purifying the silicon is energy intensive and can release harmful toxins into the environment.
The manufacturing process for solar panels also requires a lot of water, which can strain local water supplies.
Solar panels also contain toxic materials like lead and cadmium, which can be harmful if they are released into the environment.
Finally, most solar panels end up in landfills when they are no longer working. So, while solar panels are made out of environmentally friendly materials, there are some drawbacks to their use.
Are solar panels recyclable?
Solar panels are mainly made of glass, plastic, and metal, which can be recycled.
The silicon in solar panels can also be recycled, but the process is very energy-intensive, dangerous, and expensive.
So, while solar panels can be recycled, it is not very common.