Many people are switching to renewable energies, as this is not only good for the environment but also saves costs in the long term. It is certainly known to everyone that photovoltaic systems are powered by solar energy, which is converted into electricity. Responsible for this is the individual solar cells, whose functionality is based on physical processes. But what exactly happens in the solar cell? And how does electricity generation ultimately work?
The solar cell, the smallest part of the photovoltaic system
A solar powered generator system consists of several components, such as inverters, power storage, and solar modules that are mounted on roofs, gardens, or house walls. The solar module consists of many solar cells lined up next to each other, which are responsible for the conversion of solar energy and thus generate solar electricity.
The silicon solar cell is the smallest element in a PV system. They are located on the carrier material, mostly glass, and are protected from the weather by other materials on the front and back. There is also an anti-reflective layer above the solar cells, which prevents light reflections and thus prevents energy loss.
Structure of the solar cell
A solar cell usually works with silicon. Silicon has semiconducting properties that are excited by energies such as light and heat. Semiconductors can be influenced by other chemical elements, allowing for p- and n-doping. These silicon cell types consist of 3 main layers:
Ø Layer with n-doped silicon: This layer contains silicon and phosphorus. Silicon atoms always have 4 outer electrons, while phosphorus has 5 electrons. In the case of a connection, there is always 1 free electron left over, which creates an excess of electrons, which is responsible for the negative charge of the layer.
Ø Layer with p-doped silicon: The p-doped layer contains silicon and boron. On the other hand, Boron atoms only have 3 outer electrons, which is why there is a lack of electrons when they combine with silicon, which means that the layer has a positive charge.
Ø Boundary layer: The neutral boundary layer is created directly between and called the p-n junction.
Furthermore, the solar cell has metal contacts that transmit the generated electrical energy.
How does the solar cell generate electricity?
1. Initial situation: The electric field
The cell, therefore, has a positive and a negatively charged layer. A boundary layer forms in the middle, in which charge equalization takes place:
A few boron atoms from the p-doped layer absorb an excess electron from the n-doped layer – and thus become neutral. The neutral boundary layer is formed, with boron and phosphorus atoms, each having 4 electrons. As a result of this exchange, the area surrounding the n-doped layer is now more positively charged, while the p-doped layer is now negatively charged. There are two poles. This boundary layer, the p-n transition, prevents further exchange of the two differently charged layers. A stable electrical field is thus formed in the solar cell. Also check: solar panels mcallen tx
2. Conductivity through solar energy
If the sun is shining now, the photons from the sunlight hit the boundary layer.
This raises the electrons to a higher energy level and allows them to move freely. The added electron is released from the connection with the boron atom. This negatively charged electron is then attracted by the now positively charged n-doped layer.
3. Closed circuit
But metal contacts on the top and bottom of the solar cell are connected to a cable with a circuit in which the consumer is also integrated.
The electrons are conducted through the upper metal contact via the consumer and then return to the underside of the solar cell via the lower metal contact: the negatively charged p-doped layer. The whole thing is moving up and repeating itself inexorably – as long as the sun shines. The result is a current-generating energy flow – the closed circuit.
Types of solar cells
Many solar cells are made of semiconductor silicon. However, other cell types are already in use or are still being researched. These consist of different materials and substances with different procedures.
Ultimately, however, the principle is the same for all of them: To generate electricity, an electric field must be created and, with the help of the sun, electrons must start an energy flow.
Solar cells with silicon as a semiconductor
Monocrystalline solar panels: A monocrystalline solar cell consists of silicon wafers cut from a single-grown silicon crystal. The procedure for this is complex but effective.
Polycrystalline cells: Polycrystalline solar cells do not grow their crystal, as it is composed of several small silicon crystals. The resulting crystal is also sliced, from which the solar cell is assembled.
Thin-film solar cells (amorphous silicon): These thin-film cells consist of a substrate onto which a very thin layer of non-crystalline silicon is vapour-deposited.
Solar cells made from other materials
CIGS solar cells: In addition to amorphous silicon, other materials can be used for thin-film cells. For example, copper indium gallium diselenide is a semiconductor for the so-called CIGS solar cell.
Dye cells: Dye cells use a dye instead of a semiconductor. This absorbs the sunlight and thereby releases the electrons, which are passed on with the help of other chemical coatings. The principle is based on natural photosynthesis.
Organic thin-layer cells: The organic thin-layer cells consist of plastics based on carbon-hydrogen compounds. These are also semiconductor materials.
Tandem solar cells: For tandem cells, several solar cells made of different semiconducting materials are used and placed one on top of the other. The cells each consist of a top and a bottom layer, which can absorb and convert different light spectrum wavelengths. This should result in higher efficiency of the solar cell.
Why do you need semiconductors for a solar cell?
Semiconductors are materials that, under certain conditions, can conduct electricity or act as insulators. They are important for solar cells, which convert sunlight into electricity.
Solar cells have many interconnected photodiodes and semiconductor components that generate an electric current when exposed to light.
The most commonly used semiconductor for crystalline solar cells is silicon. Still, other semiconductors such as gallium arsenide, cadmium sulfide or zinc selenide are also used in thin film solar cells. Solar cells would not work without semiconductors.
How much voltage does a solar cell have?
The solar cell’s voltage depends on the material it is made of and the amount of sunlight it is exposed to.
A solar cell typically has a voltage of 0.60 to 0.68 volts at no load, i.e. when no load is connected, such as a battery or a light bulb. The voltage drops when a load is connected, e.g. B. when the solar cell is used to power a device.
Why do solar cells only work with sunlight?
When sunlight hits a solar cell, the silicon absorbs the photons and releases electrons. The electrons flow through the cell, creating an electric current.
Silicon solar cells only work with sunlight because they rely on the photons in sunlight to generate electricity. Photons are light particles, and sunlight consists of a wide range of photons with different energies.
Solar cells can only be optimized for photons in a specific energy spectrum. If this should not happen, the photons cannot be absorbed, so they cannot be converted into electricity.
However, solar cells can also generate electricity in the shade or without the sun. The cells absorb the light molecules contained in the diffuse radiation and generate solar power from them. However, solar cells generate only a small amount of electricity under these conditions because they are not exposed to direct sunlight.
How many cells does a solar module have?
Solar modules consist of a series of solar cells. The most common type of solar cell is made of silicon, and the typical size of a solar cell is 156mm x 156mm or 6 inches. Small solar panels used on residential rooftops have 60 of these silicon cells.
Can you build a solar cell yourself?
Solar cells are a great way to generate electricity from renewable resources. This project will show you how to build a solar cell yourself.
Ø First, take a glass plate coated with TiO2 and put it in hibiscus tea for five minutes. This will turn the coating purple.
Ø While the titanium dioxide plate is being coloured, you can prepare the counter electrode. First, clean the conductive side of the plate with water and a cleaning cloth. You have to coat this glass plate with graphite. To do this, take a soft pencil and paint the surface.
Ø After the titanium dioxide electrode has been stained, you will need to rinse it under water to wash away the excess dye. The solar cell will not function properly if you don’t do this. Dry the electrode with a hair dryer.
Ø Next, place the two glass plates on top of each other and offset them slightly so the tension can dissipate.
Ø Finally, you run the iodine solution between the glass plates. If you connected a multimeter, you could see how a voltage is displayed when the room is lit.
With a little effort, you can build your solar cell and take advantage of this clean, renewable energy source.
Benefits of solar energy
Why are solar cells environmentally friendly?
Solar technology is based on natural resources and physical processes that are environmentally friendly, climate-neutral and renewable. While our traditional electricity is generated from fossil energy, which is obtained by burning fossil fuels such as coal and petroleum, Solar cells draw their energy directly from sunlight, stimulating the energy flow of the electrons.
Solar energy does not consume any fossil fuels and is resource-friendly. Since solar energy is not generated by combustion, no CO2 is released either. Without CO2 emissions, the climate cannot be harmed.
Solar panels save on electricity costs
Solar energy is free. A off-grid 12 volt batteries system with power storage can reduce or even completely prevent using the usual grid power. So no more electricity costs have to be paid for additional, conventional electricity.
After some time, the electricity cost savings offset the photovoltaic system’s acquisition costs. Many different subsidy programs offer loans that make a solar system feasible for everyone.
There are many types of solar cells, some of which are still in the research stage. In the future, the generation of energy and the efficiency of solar cells can be improved even further. Renewable energies are becoming increasingly efficient – and of course, protecting our environment.
Solar energy does not consume any fossil fuels and is resource-friendly. Since solar energy is not generated by combustion, no CO2 is released either. Without CO2 emissions, the climate cannot be harmed.