Panels photovoltaic solar energy

Types Of Photovoltaic Cells

Types Of Photovoltaic Cells

Photovoltaic cells are responsible for converting solar radiation into electrical energy in the form of direct current. Photoelectric cells are an indispensable element for this type of renewable energy.

There are different types of photoelectric cells depending on the nature and characteristics of the materials used. The most common type is the crystalline silicon cell (Si). This material is cut into very thin sheets in the shape of a disc, monocrystalline or polycrystalline, depending on the manufacturing process of the silicon bar.

The first crystalline cell that was manufactured in the industrial field is that of pure monocrystalline silicon. These types of solar cells have good energy efficiency, but have a higher cost than other types. For this reason, they currently have a moderate level of implementation.

The series of photovoltaic cells connected in series form a solar panel. In this case, a photovoltaic solar panel.

Monocrystalline and polycrystalline solar cells

Monocrystalline solar cells usually have a square shape, with rounded corners. Formerly they had a circular shape. This is due to the growth process of the monocrystalline silicon crystal that has a cylindrical shape.

Monocrystalline and polycrystalline photovoltaic cells

In the manufacturing process of polycrystalline silicon, silicon is allowed to slowly solidify in a rectangular mold and a rectangular solid with many crystals is obtained, which gives rise to polycrystalline cells. These types of cells have a lower performance than monocrystalline, but currently have a strong implantation because they have a lower economic cost than monocrystalline.

With less implementation, we can find in the market photovoltaic panels called "thin film". These are not manufactured with individual cells, but in the form of continuous bands in which a thin layer of amorphous silicon (a-Si), 1 or 2 microns thick, is deposited on an appropriate substrate (glass or synthetic resins), making a continuous panel that does not need interior interconnections.

A characteristic of these cells is that the photons that do not collide with any electron cross them thanks to their small thickness, which allows the design of panels with different overlapping layers and that are called tandem (two layers) or triple junction (three layers) .

Amorphous silicon cells have a yield of approximately half that of crystalline cells, and therefore, other types of semiconductors, essentially copper and indium selenur (CIS), are beginning to be used in the manufacture of thin-layer cells. or cadmium tellurium (CdTe).

SiliconAs innovative technologies in the manufacture of photovoltaic cells, we will highlight the so-called "HIT cells" (Heterojunction with Intrinsic Thin Layer). This term refers to a technique based on the superposition of semiconductor layers of different "gap" such as amorphous silicon combined with crystalline silicon cells or cadmium tellurium, etc.

This improves the energy efficiency of solar cells and broadens the spectrum of usable solar radiation, since each of the semiconductors is especially sensitive to some of the electromagnetic spectrum bands.

Thin film solar cell

A solar film cell is a solar cell that is manufactured by depositing one or more thin layers of photovoltaic material on a substrate. This type of photovoltaic cell also called thin film photovoltaic cell. The thickness range of this layer is very wide and varies from a few nanometers to tens of micrometers.

Many of the photovoltaic materials are manufactured with different deposition methods on a variety of substrates. Thin film solar cells are usually classified according to the photovoltaic material used:

  • Dye-sensitized solar cells (DSC) and other organic solar cells.
  • Indian copper gallium and selenium (CIS or CIGS)
  • Cadmium Telluride (CdTe)
  • Amorphous silicon (a-Si) and other thin film silicon (TF-Si)

Solar concentration systems

Another of the technological innovation lines developed in recent years is the so-called solar concentration technique, which allows to improve the use of renewable energy per square meter of photovoltaic panel.

This technology is based on the concentration of solar radiation on a small surface (the photovoltaic cell) through an optical concentrator. For example, through a Fresnel lens (magnifying glass effect) or a reflector, such as a simple mirror with which a significant increase in incident solar radiation can be achieved and, consequently, a larger energy efficiency of the system. This technique is also known as a solar oven.

In any case, the concentration systems have the disadvantage that they use almost only direct solar radiation. Therefore, with the concentration panels it is essential to use precise monitoring systems.

Currently, the market offers some photovoltaic panels with spot Fresnel concentrator systems and other disk-parabolic concentrators integrated in the same panel, which can increase the incident radiation in the cell up to 500 times, and thus significantly increase production energy per unit cell surface.

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References

Last review: September 26, 2019