Photovoltaic solar panels are made up of different types of solar cells, which are the elements that generate electricity from solar energy.
The main types of photovoltaic cells are the following:
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Monocrystalline silicon solar cells (M-Si) are made of a single silicon crystal with a uniform structure that is highly efficient.
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Polycrystalline silicon solar cells (P-Si) are made of many silicon crystals and have lower performance.
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Thin-film cells are obtained by depositing several layers of PV material on a base.
The different types of PV cells depend on the nature and characteristics of the materials used.
What is a solar cell?
A solar cell is the essential part of a solar panel that captures and converts solar radiation into electrical energy. It is possible thanks to the fact that they are manufactured with a semiconductor material, usually silicon.
When an atom of silicon receives photons from solar rays provokes a displacement of an electron and results in a direct current (DC).
Indeed, a single solar cell is incapable of being able to generate energy to supply the home. For this reason, PV panels are built with a set of several solar cells. The sum of the current and voltage of several solar cells generates a suitable electric current.
Depending on solar cells' use, we can connect a power inverter to transform DC into AC after the solar panels.
This form of generating electricity is considered a clean, renewable energy source. In addition, it is an alternative to fossil fuels that emits greenhouse gases and are directly responsible for climate change.
What are the materials used for PV cells?
The primary material used in the manufacturing of PV solar cells is silicon.
It is the second most abundant element in the Earth's crust (27.7% by weight) after oxygen. It occurs in amorphous and crystallized forms. The first is a brownish powder, more active than the crystalline variant, which occurs in blue-gray octahedrons with a metallic sheen.
Pure silicon does not exist in a free state, but is found in the form of silicon dioxide and complex silicates. Minerals containing silicon constitute about 40% of all common minerals, including more than 90% of the minerals that form volcanic rocks.
It is a very abundant semiconductor material. It is widely used in electronics as a primary material for creating silicon wafers or chips. Then, these wafers and chips can be implanted into transistors, solar cells, and a wide variety of electronic circuits.
Monocrystalline solar cells
The first crystalline cell manufactured in the industrial field is that of pure monocrystalline silicon. These types of solar cells have good energy performance but have a higher cost than other types. For this reason, they currently have a moderate level of implementation.
This type of solar cell usually has a square shape, with rounded corners (previously, they were circular). It is due to the growth process of the monocrystalline silicon crystal that has a cylindrical shape.
These are the most outstanding features:
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The heating process is slower.
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Its manufacturing process is more energetically expensive.
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It is more efficient than the other types of solar cells because the silicon atoms are perfectly aligned.
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The manufacturing process is longer.
To denote the crystal directions, single crystal wafers often have flats to indicate the orientation of the wafer and the doping.
Polycrystalline solar cells
In the polycrystalline silicon manufacturing process, the silicon is slowly allowed to solidify in a rectangular mold, resulting in a rectangular solid with many crystals. These cells are the most common for medium and low-power PV plants.
Solar panels with this cell type are cheaper but have lower electrical energy performance.
Polycrystalline solar panels differ from monocrystalline panels because they have more excellent resistance to overheating, and their operation is optimal in usually hot climates.
The color of this type of solar cell is dark blue which lets us detect if a panel belongs to this type of cell. Those solar panels with dark blue cells are polycrystalline solar panels.
Another difference between both types of PV cells is that it does not have rounded edges but are completely rectangular, forming 90º angles.
Thin film solar cells
"Thin film" modules are not manufactured with individual cells but in the form of continuous bands deposited on an appropriate substrate. The layers are made of amorphous silicon (a-Si) 1 or 2 microns thick and do not need internal connections.
A characteristic of this type of panel is that the photons that do not collide with any electrons pass through them thanks to their small thickness. This feature enables the design of panels with different superimposed layers.
One of the types of thin film cells is the amorphous silicon cell. Thin film solar panels with amorphous silicon have a performance of about half that of crystalline cells. For this reason, other types of semiconductors are beginning to be used.
What are the types of thin film solar cells?
Many of the materials are manufactured using different deposition methods on various substrates. Thin-film solar cells are usually classified according to the photovoltaic material used:
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Dye-sensitized solar cells (DSC) and other organic solar cells.
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Copper indium gallium and selenium (CIS or CIGS)
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Cadmium telluride (CdTe)
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Amorphous silicon (a-Si) and other thin-film silicon (TF-Si)
Amorphous silicon solar cells
They are one of the best-known types of solar cells. They have great flexibility in their composition, making their adaptation and resistance more remarkable than the other alternatives.
This type of PV solar cell is cheaper to produce. However, it is not suitable for use in solar panels because its use of solar energy is too low to supply any project.
Types of solar panels according to the number of solar cells
Likewise, a solar panel can be classified by the number of solar cells it contains.
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36 cells: This type of solar panel is designed to have an approximate power of 150 W.
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60 cells and 120 half cells: 24V solar panels have power between 320W to 340W.
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72 cells and 144 half cells: They have power between 385W and 415W. They are usually used for self-consumption projects.
What consists of PERC technology?
PERC technology ( Passivated Emitter Rear Cell) is known for placing a reflective layer for better use of radiation. That is, it refers to the extra layer installed on the back of the solar panel to increase the total efficiency of a solar panel.
Distributors and manufacturers currently prefer this type of solar cell due to its innovative technology.
What are solar concentration systems used for?
Another line of innovation in recent years is solar concentration, which allows improving the use of renewable energy per square meter of solar panel.
This technology is based on the concentration of solar radiation on a small surface using an optical concentrator. Therefore, the concentrator aims to significantly increase the incident solar radiation because it takes advantage of a broader solar spectrum and, consequently, the power capacity.
In any case, concentration systems can almost only take advantage of direct solar radiation. Therefore, this type of solar panel needs a solar tracker.
Concentration systems are also used in solar thermal plants to generate electricity or to obtain domestic hot water.