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Solar cells, also known as photovoltaic cells, have the ability to turn incident sunlight into electricity.
How does a solar cell work? What is a photovoltaic process?
Solar cells are the basic components of photovoltaic panels that change the sun’s rays into electricity. This is due to the photovoltaic process. In the first stage, light absorption occurs. Photons incident on the surface of the solar cell are captured. Each photon carries a certain amount of energy. The process of absorbing photons is made possible by a semiconductor material (usually silicon).
In the next steps are created the so-called “new”. electron-hole pairs and separation of electron-hole pairs occurs. In the next stage, current flows. Electrons are attracted to the n side of the cell, while holes begin to move to the p side of the cell.
As the holes move in the opposite direction to the electrons, a current flow is generated. The penultimate stage is the extraction of electric current, that is, the flow of electrons through an external circuit, such as directly into a battery. During the flow through the outer circuit, the final recombination with the holes located in the semiconductor material takes place.
Construction of the solar cell
Each photovoltaic cell is composed of several components that perform different functions. The semiconductor layer is among the most important parts of a solar cell. This part is mostly made of silicon. Depending on the specific cell model, the silicon can be polycrystalline, monocrystalline or amorphous. The next elements are the conductive electrodes, which are thin layers of metal (e.g. silver) that are located on both the bottom and top of the cell. The two main tasks of conductive electrodes are to collect and transmit electric current.
The next part of the solar cell is the anti-reflective layer (usually made of silicon oxide). This component is mounted on top of the cell and is responsible for reducing the reflection of sunlight, thus improving the performance of the photovoltaic module. To protect the photovoltaic cell, manufacturers use protective glass and frames. A photovoltaic module protected in this way is resistant to external factors such as snow, rain and dust.
What is the difference between polycrystalline and monocrystalline cells?
The poly and monocrystalline cell perform an identical function in the entire photovoltaic system. In both cases, silicon in crystalline form is used for production. The most important difference between polycrystalline and monocrystalline cells is the so-called “polycrystalline cell”. crystal clarity. In the case of monocrystalline panels, we are dealing with a single piece of silicon crystal. Polycrystalline cells, on the other hand, use multiple fragments of silicon that are interconnected. This means that the purity in polycrystalline panels is lower than in monocrystalline panels.
Another difference is efficiency, or the ability to convert a certain amount of solar energy into electricity. The efficiency of monocrystalline panels, depending on the specific manufacturer, ranges from about 16% to about 25%. In contrast, the efficiency of polycrystalline panels ranges from about 14% to about 19%. In practice, this means that the same area of monocrystalline panels will produce more energy than the area of polycrystalline panels under the same operating conditions.
Other differences
Monocrystalline solar panels in residential and commercial installations also have another important advantage. Energy production starts earlier and ends later (on a daily cycle), compared to polycrystalline models. There are also differences in cell performance at high temperatures. Polycrystalline cells show lower efficiency when exposed to high temperatures than monocrystalline models. The cost of producing a cell consisting of a single piece of silicon crystal is higher than producing panels from multiple silicon crystals joined together. Differences also include the appearance of photovoltaic modules. Monocrystalline models are distinguished by their uniform black surface. Monocrystalline versions, on the other hand, may have a blue tint and a uniform surface, which is the result of different angles of light reflection by individual silicon crystals.
It is also worth mentioning that both types of panels have a similar lifespan of about 30 years. Performance should not change much during this period. It is estimated that about 98% of all photovoltaic installations in Poland use polycrystalline cells to capture and produce electricity from the sun.
Low power solar cells
Low-power solar panels provide an alternative source of energy in DIY projects, for example. They are perfect for building devices that can operate for years without access to mains power. Low-power solar cells are small devices with dimensions of a few to 30 cm. The various models differ not only in output power, but also in the rated voltage produced, and thus in application.
Selected low-power solar cells are factory-equipped with soldering pads for soldering the wires. Other models, on the other hand, already have an outgoing cable terminated, for example, with a USB type A connector. Particularly noteworthy are the flexible photovoltaic panels, which can be successfully mounted, for example, on slightly curved surfaces.
Ready-made low-power photovoltaic modules
You can also find ready-made photovoltaic modules on the market. A good example is compact modules designed to charge a lithium-polymer cell using solar radiation. The solar panel itself is protected from the elements. In addition, the module is equipped with the necessary safety features (including an integrated solar controller).
