What is photovoltaic technology? Photovoltaic (PV) technology is a technology that generates energy using devices that absorb energy from sunlight and convert it into electricity using semiconductor materials. These solar cells, are connected to form modules to generate more significant amounts of electricity.
When the surface of a solar panel is radiated by electromagnetic radiation at a frequency more significant than the cutoff frequency the electrons will absorb the energy from the photons and generate electricity.
Electrons will not emit if the radiated frequency is less than the cutoff frequency because the electron does not provide the necessary energy to pass. Electrons emitted under the effect of electromagnetic radiation will be called photoelectric.
Meaning Of Silicon Semiconductor Materials
The most popular semiconductor material used to create solar cells is Silicon, which is cut into small and thin sheets.
Some silicon wafers can be alloyed by some suitable chemical element to create an electron imbalance in the sheet.
The panels are stacked together to form a complete solar panel.
When the photon reaches the solar photovoltaic cell, one of three possibilities occurs:
- Photons are absorbed by photovoltaic cells
- Photon is reflected away by the photocell.
- Photon passing through the photovoltaic cell
How does the intensity of sunlight affect?
When Si (Silicon) absorbs photons, an electric current will be generated. This means that the stronger the intensity of the light (i.e. the more photons hitting the panel’s surface), the greater the amperage.
Therefore, photovoltaic cells not only generate a lot of electricity on sunny days but can also generate electricity on cloudy days, even some panels equipped with new technology can now generate electricity. Small electricity in the moonlit night.
Photovoltaic cells, if placed separately, will generate a reasonably small current. So, to get a strong enough capacity, manufacturers will connect them into a complete module (1 module, also known as a solar panel).
A panel will have 60 cells or 72 cells of photovoltaic panels.
Learn photovoltaic technologies
When light hits a photovoltaic (PV) cell — also known as a solar cell — that light can be reflected, absorbed, or passed through the cell. PV cells are composed of semiconductor materials; “semi” means it can conduct electricity better than an insulator but not as good as a conductor like metal. There are several different semiconductor materials used in PV cells.
When a semiconductor is exposed to light, it absorbs the light’s energy and transfers it to negatively charged particles in the material called electrons. This additional energy allows electrons to flow through the material as an electric current. This current is extracted through conductive metal contacts – grid-like lines on solar cells – and can then be used to power your home and the rest of the grid electricity.
The efficiency of a PV cell is simply the amount of electrical power leaving the cell relative to the energy from the light hitting it, indicating how efficiently the cell is at converting energy from one form to another. another form. The amount of electricity generated from PV cells depends on the characteristics (such as intensity and wavelength) of the light available and the many performance properties of the cell.
An essential property of PV semiconductors is the frequency band, which indicates the wavelength of light that the material can absorb and convert into electrical energy. If the band of the semiconductor matches the wavelength of light hitting the PV cell, then the cell can efficiently use all available energy.
By far, Silicon is the most common semiconductor material used in solar cells, accounting for about 95% of the modules sold today. It is also the second most abundant material on Earth (after oxygen) and the most common semiconductor used in computer chips. Crystalline silicon cells are made of silicon atoms connected to form a lattice, and this lattice provides an organized structure that converts light into electricity more efficiently.
Solar cells made from Silicon currently offer a combination of high efficiency, low cost and long life. Modules are expected to last for 25 years or more, still generating more than 80% of their original performance after this time.
Thin-film solar cells are made by placing one or more thin layers of PV material on a supporting material such as glass, plastic or metal. There are two main types of thin-film PV semiconductors on the market today: cadmium telluride (CdTe) and copper indium gallium diselenide (CIGS). Both materials can be placed directly on the front or back of the module surface.
CdTe is the second most common PV material after Silicon, and CdTe cells can be made using a low-cost manufacturing process. While this makes them a cost-effective alternative, their performance is still not as high as Silicon’s. CIGS cells have optimal properties for PV materials and are highly efficient in the laboratory, but the complexity involved in combining the four factors makes the transition from laboratory to production a breeze. More difficult. Both CdTe and CIGS require more protection than Silicon for long-term outdoor operation.
Perovskite solar cells are a type of thin-film cell and are named for their characteristic crystal structure. Perovskite cells are built with layers of material printed, coated, or vacuum-sealed onto an underlying support layer, known as the substrate. They are generally easy to assemble and can achieve similar performance to crystalline Silicon. In the lab, the performance of perovskite solar cells has improved faster than any other PV material, from 3% in 2009 to more than 25% in 2020. To become commercially usable , perovskite PV cells must become stable enough to last 20 years outdoors, so researchers are working to make them more durable and develop low-cost, large-scale manufacturing techniques. .
Organic PV cells, or OPVs, are composed of carbon-rich (organic) compounds and can be tuned to enhance a specific PV cell function, such as ribbon, transparency. or color. OPV cells are currently only half as efficient as crystalline silicon cells and have shorter runtimes but can be less expensive to produce in large volumes. They can also be applied to a variety of support materials, such as flexible plastics, making OPVs able to serve a variety of uses.
Quantum dot solar cells conduct electricity through microscopic particles of various semiconductor materials just a few nanometers wide, known as quantum dots. Quantum dots offer a new way to process semiconductor materials, but making electrical connections between them is difficult, so they’re currently inefficient. However, they are straightforward to make into solar cells. They can be deposited onto the surface by rotary coating, inkjet or roll printers such as those used for newspaper printing.
Quantum dots come in various sizes, and their frequency bands are customizable, allowing them to collect elusive light and be coupled with other semiconductors, like perovskites, to optimize their performance. Multifunctional solar cells (more on these below).
Another strategy to improve PV battery efficiency is to layer semiconductors to create multifunctional solar cells. These cells are essentially stacks of dissimilar semiconductor material instead of single-junction cells with only one semiconductor. Each layer has a different frequency band, so each layer absorbs a different part of the solar spectrum, taking advantage of more sunlight than single contiguous cells. Multifunctional solar cells can reach record efficiency levels because light not absorbed by the first semiconductor layer is captured by the layer below it.
While all solar cells with more than one band are multi-band solar cells, a solar cell with precisely two bands is called a tandem solar cell. Multifunctional solar cells that combine semiconductors from columns III and V in the periodic table are called III-V multifunctional solar cells.
Multifunctional solar cells have proven to be 45% more efficient, but they are expensive and difficult to manufacture, so they are dedicated to space exploration. The military uses III-V solar cells in drones, and researchers are exploring other uses where high efficiency is critical.
Converged PV, also known as CPV, focuses sunlight onto a solar cell using mirrors or lenses. By focusing sunlight on a small area, less PV material is needed. PV materials become more efficient as light is concentrated, so the highest overall efficiency is obtained with CPV cells and modules. However, it requires more expensive materials, manufacturing techniques, and the ability to track the sun’s motion, so demonstrating the necessary cost advantage over today’s high-volume silicon modules has now become problematic.