What is Solar Cell?
A solar cell or photovoltaic cell is an electrical device that converts the energy of light directly into electricity through the photovoltaic effect. It is a form of the photoelectric cell defined as a device whose electrical properties, such as current, voltage, or resistance, change when exposed to light.
Individual solar cell devices are often the electrical components of photovoltaic modules, colloquially known as solar panels. The common single-junction silicon solar cell can produce a maximum open-circuit voltage of approximately 0.5 volts to 0.6 volts.
Solar cells are called photovoltaics, regardless of whether the source is sunlight or artificial light. In addition to generating energy, they can be used as photodetectors (e.g., infrared detectors), to detect light or other electromagnetic radiation in the visible range, or to measure light intensity.
The operation of a photovoltaic (PV) cell requires three basic properties:
- The absorption of light that creates either electron-hole pairs or excitons.
- The separation of charge carriers of opposite types.
- The separate removal of these carriers to an external circuit.
In contrast, a solar thermal collector provides heat by absorbing sunlight, either for direct heating purposes or to generate electricity indirectly from heat. A “photo electrolyte cell”, on the other hand, refers to either a type of photovoltaic cell or a device that splits water directly into hydrogen and oxygen using solar radiation.
Photovoltaics and solar panels are the two means of generating solar power.
For more information read our article: 1. What is Solar energy? 2. What is Solar penal? 3. What is a solar power system( off-grid and on-grid)?
Construction of Solar Cells
Most photovoltaic solar cells or PV cells are made from crystalline silicon wafers. The wafers can be one of two main types, monocrystalline (mono) or polycrystalline (poly), also known as multi-crystalline. The most efficient type is monocrystalline, which is produced using the well-known Czochralski process.
A solar cell is basically a junction diode, although its Construction differs slightly from conventional p-n junction diodes. A very thin layer of a p-type semiconductor is grown on a relatively thicker n-type semiconductor. Then we put some finer electrodes on top of the p-type semiconductor layer.
These electrodes do not prevent light from reaching the thin p-layer. There is a p-n junction just below the p-layer. We also provide a current collecting electrode at the bottom of the n-layer. We encapsulate the entire assembly with thin glass to protect the solar cell from mechanical impacts.
The output voltage and current obtained from each unit of the cell are very small. The output voltage is 0.6V and the current is 0.8V. The various combinations of cells are used to increase output efficiency.
Solar cell Diagram
How do solar cells work?
When sunlight hits a solar cell, electrons are ejected from the silicon, which creates “holes” – the vacancies left behind by the escaping electrons. When this happens in the electric field, the field moves electrons to the n-layer and holes to the p-layer.
When you connect the n-type and p-type layers with a metal wire, the electrons migrate from the n-type layer to the p-type layer by crossing the depletion zone and then through the external wire back of the n-type layer, creating a flow of electricity.
A solar cell is a sandwich of n-type silicon and p-type silicon. It creates electricity by using sunlight to bounce electrons across the link between the different flavors of silicon:
- When sunlight shines on the cell, photons (particles of light) bombard the upper surface.
- The photons carry their energy down through the cell.
- The photons give their energy to electrons in the lower p-layer.
- The electrons use this energy to jump over the barrier into the upper, n-conductive layer and to escape into the circuit.
- The electrons flow around the circuit and generate electricity.
Types of Solar cell
A solar cell is a solid-state electrical device that converts the energy of light directly into electricity by the photovoltaic effect, which is a physical and chemical phenomenon.
It is a form of photoelectric cell, defined as a device whose electrical characteristics, such as current, voltage, or resistance, vary when exposed to light.
The following are the different types of solar cells.
- Amorphous Silicon solar cell (a-Si)
- Biohybrid solar cell
- Cadmium telluride solar cell (CdTe)
- Concentrated PV cell (CVP and HCVP)
- Copper indium gallium selenide solar cells (CI(G)S)
- Crystalline silicon solar cell (c-Si)
- Float-zone silicon
- Dye-sensitized solar cell (DSSC)
- Gallium arsenide germanium solar cell (GaAs)
- Hybrid solar cell
- Luminescent solar concentrator cell (LSC)
- Micromorph (tandem-cell using a-Si/μc-Si)
- Monocrystalline solar cell (mono-Si)
- Multi-junction solar cell (MJ)
- Nanocrystal solar cell
- Organic solar cell (OPV)
- Perovskite solar cell
- Photoelectrochemical cell (PEC)
- Plasmonic solar cell
- Polycrystalline solar cell (multi-Si)
- Quantum dot solar cell
- Solid-state solar cell
- Thin-film solar cell (TFSC)
- Wafer solar cell, or wafer-based solar cell crystalline
- Non concentrated hetrogeneos PV cell
The three different types of solar modules are monocrystalline, polycrystalline, and thin-film solar modules. Each of these types of solar cells is manufactured in a unique way and has a different aesthetic appearance. Here is the breakdown for each type of solar panel.
Monocrystalline Solar Panels
Monocrystalline solar panels are the oldest and most developed type of solar panel. These monocrystalline solar panels consist of around 40 monocrystalline solar cells. These solar cells are made of pure silicon.
During production (the so-called Czochralski process), a silicon crystal is placed in a tub of molten silicon. The crystal is then pulled out of the vat very slowly so that the molten silicon forms a solid crystal shell around it called an ingot. The ingot is then thinly cut into silicon wafers. The wafer is processed into the cell, and then the cells are assembled to form a solar panel.
Monocrystalline solar cells appear black due to the way sunlight interacts with pure silicon. While the cells are black, there are a variety of colors and designs for the backs and frames. The monocrystalline cells are square in shape with the corners removed so that there are small gaps between the cells.
Polycrystalline Solar Panels
Polycrystalline solar panels are a recent development, but their popularity and efficiency are increasing rapidly. Like monocrystalline solar modules, polycrystalline cells are made of silicon. But polycrystalline cells are made up of fused pieces of silicon crystal.
During the manufacturing process, the silicon crystal is placed in a vat of molten silicon. Instead of pulling it out slowly, you let this crystal shatter and then cool. After the new crystal has cooled in its shape, the fragmented silicon is thinly cut into polycrystalline solar wafers. These wafers are assembled to form a polycrystalline panel.
Polycrystalline cells are blue in color due to the way sunlight reflects off the crystals. Sunlight is reflected differently from silicon fragments than from a pure silicon cell. Usually, the back frames and frames are silver with polycrystalline material, but there may be variations. The shape of the cell is square and there are no gaps between the corners of the cells.
Thin-Film Solar Panels
Thin film solar panels are an extremely new development in the solar panel industry. The most salient feature of thin-film panels is that they are not always made of silicon. They can be made from a variety of materials including cadmium telluride (CdTe), amorphous silicon (a-Si), and copper indium gallium selenide (CIGS).
These solar cells are made by sandwiching the main material between thin sheets of conductive material with a layer of glass on top for protection. Although the a-Si panels use silicon, they use non-crystalline silicon and are also covered with glass.
As the name suggests, thin-layer panels are easy to recognize by their thin appearance. These panels are about 350 times thinner than those using silicon wafers. But thin-film frames can sometimes be large, and that can compare the appearance of the entire solar system to that of a mono- or polycrystalline system. Thin-film cells can be black or blue, depending on the material.
Material Uses in Solar Cell
Solar cells are typically named after the semiconducting material they are made of. These materials must have certain characteristics in order to absorb sunlight.
- Crystalline silicon
- Amorphous Silicon (a-Si)
- Copper-Indium Gallium Diselenide (CIGS)
- Gallium arsenide thin film
- Cadmium Telluride (CdTe)
- Monocrystalline silicon
- Epitaxial silicon development
- Polycrystalline silicon
- Ribbon silicon
- Mono-like-multi silicon (MLM)
Advantages of Solar Cell
- Renewable energy: The energy can be used to generate electricity as well as heat in the house, either through solar PV or solar thermal energy.
- Economical Energy: Solar cells are a great way to save money on your electricity bill because you don’t pay for the energy you generate.
- Environmentally friendly energy: There is almost no pollution with solar cells. Discharge of waste and pollution are inevitable in connection with the manufacture of solar cells.
- Innovative energy: Photovoltaics is a popular topic in green energy and is considered a good solution for preventing climate change.
- Infinite Energy: If you have the ability to draw energy from the sun’s rays, it is a source of energy that will never be depleted.
- Long-term energy: PV systems often have a long service life and a good service life.
- Selling energy: If your home has solar panels, it is often easier to sell the property at a higher price.
Disadvantages of solar cell
- Interior needs: Not all households that meet their requirements and can get the most out of their solar cells.
- High investment requires: The installation costs for solar modules are relatively high.
- Seasonal energy: Compared to other types of renewable energies, the solar power plant is highly seasonal.
- Difficult to install Solar panels in your home: It may be more difficult to install solar panels in older households as they often have different designs that can provide shade.
Use of Solar Cell
- Solar cells are very useful in powering space vehicles such as satellites and telescopes.
- It may be used to charge batteries.
- Used in light meters.
- It is used to power calculators and wristwatches.
- It can be used in spacecraft to provide electrical energy.