If light hits a photovoltaic (PV) cell, which is also known as a solar cell, the light can bounce back, stay on the cell, or pass right through it. “Semi” means that the material that makes up the PV cell can carry electricity better than an insulator but not as well as a good conductor like metal. PV cells use a number of different kinds of semiconductors.
When light hits the semiconductor, it takes in the energy of the light and sends it to electrons, which are negatively charged particles in the material. Because of this extra energy, the electrons can move through the object as a current of electricity. The grid-like lines on solar cells are conductive metal contacts that pull this current out. This current can then be used to power your home and the rest of the electric grid.
The efficiency of a PV cell is just the ratio of the electricity that comes out of the cell to the energy that comes from the light shining on it. This shows how well the cell changes energy forms. The amount of energy that PV cells make relies on the light that is available, including its strength and colors, as well as the cell’s success in a number of areas.
A PV cell doesn’t always turn the sunlight that hits it into power. It’s actually lost most of it. A solar cell’s ability to turn sunlight into electricity is limited by a number of design factors. More efficiency can be reached by designing with these things in mind.
Wavelength
Light is made up of photons, which are energy packets that come in a lot of different colors and strengths. From ultraviolet to infrared, the bands of sunshine that reach the earth’s surface are all different. Few photons are reflected when light hits the surface of a solar cell. Other photons go right through. Some of the photons that are taken in have their energy changed into heat. The rest have just the right amount of energy to break electrons free from their atomic bonds, which creates charge carriers and an electric current.
Recombination
A “charge carrier,” like an electron with a negative charge, can move across a semiconductor so that electricity can flow through it. A “hole,” which is simply the lack of an electron in a material, is another type of charge carrier that works like a positive charge carrier. When an electron meets a hole, they might join back together, which would cancel out their inputs to the current. Light-generated electrons and holes bump into each other, reunite, and send out a photon. This is the opposite of the process that makes power in a solar cell. One of the main things that affects productivity is this. Indirect recombination is when electrons or holes come across an impurity, a flaw in the crystal structure, or a contact that makes it easier for them to join back together and give off heat.
Temperature
Most of the time, solar cells work best when it is cold outside. When the temperature goes up, the qualities of the semiconductor change, which makes the current go up a little but the voltage go down a lot. Extreme temperature rises can also hurt the cell and other materials in the module, which shortens their useful lives. A lot of the sunshine that hits cells turns into heat, so managing heat well makes them work better and last longer.
Reflection
Cutting down on the amount of light that bounces off the surface of a cell can make it work better. Silicon, for instance, returns more than 30% of light that hits it when it is not handled. Coatings and surfaces with roughness that don’t reflect light help cut down on reflection. A cell that works well will look dark blue or black.
Solar Cell Materials
Silicon is the most common semiconductor used in computer chips and the second most common element in the universe, after oxygen. Crystalline silicon cells are made up of silicon atoms that are linked together to make a crystal structure. This grid gives the structure a neat look that makes turning light into electricity work better.Silicon solar cells are currently the best because they are highly efficient, cheap, and last a long time. Modules should last at least 25 years and still produce more than 80% of the power they did when they were first made.
Thin-film solar cell by putting down one or more thin pieces of PV material on a base material like metal, glass, or plastic. Today, cadmium telluride (CdTe) and copper indium gallium diselenide (CIGS) are the two main types of thin-film PV semiconductors available. You can put both elements straight on the front or back of the module’s surface.
Perovskite solar cells are a type of thin-film cell, and their name comes from the way their crystals are arranged. Perovskite cells are made by printing, coating, or vacuum-depositing layers of chemicals onto a support layer below. This layer is called the substrate. They are usually simple to put together and can work as efficiently as pure silicon.
Organic Photovoltaic (OPV) cells are made up of carbon-rich (organic) substances that can be changed to improve a PV cell’s function, like its bandgap, color, or clarity. At the moment, OPV cells are only about half as efficient as solid silicon cells. They also have shorter useful lives, but they might be cheaper to make in large quantities. They can also be used on different types of support materials, like flexible rubber, which means that OPV can be used for many different things.
Quantum dots are very small bits of different semiconductor materials that carry power through solar cells. They are only a few nanometers thick. Quantum dots offer a fresh method for working with semiconductors, but it’s hard to make an electrical link between them, so they’re not very useful right now. They are, however, simple to turn into solar cells.
Multijunction PV:These cells are stacks of different semiconductor materials. Single-junction cells, on the other hand, only have one semiconductor. Because every layer has a different bandgap, they all receive a different range of wavelengths from the sun. This means that they use more energy than single-junction cells. It is possible for multijunction solar cells to be very efficient because light that doesn’t get absorbed by the first layer of semiconductors is picked up by a layer below it.
Multijunction solar cells have been shown to be more than 45% efficient, but they’re expensive and hard to make, so they’re only used for space travel. III-V solar cells are used by the military in drones, and scientists are looking for other ways to use them in situations where high efficiency is important.
Concentration PV:Focusing sunshine on a solar cell with a mirror or lens is what concentration PV, also called CPV, does. Less PV material is needed because the sun is focused on a small area. With CPV cells and modules, you get the best total efficiency because PV materials work better when the light is more concentrated. However, they need more expensive materials, better production methods, and the ability to watch the sun’s movement, which makes it hard to show that they are cheaper than today’s high-volume silicon modules.
Consersion Efficiency
Check how well a PV device works to guess how much power the cell will make. Current and voltage together make up electrical power. The electrical properties of PV devices can be measured by their current-voltage relationships. Ohm’s law says that the current through a circuit between two points is directly related to the difference in potential between those two places. If a certain “load” resistance is connected to the two ends of a cell or module, the current and voltage will change. To find the efficiency, you keep the cell at a steady temperature and expose it to a normal amount of light. Then, you measure the current and voltage that are made for different load resistances.
Extreme Conditions
Sometimes solar panels do really well in really bad weather because that’s how they were made. But solar panels can make less power when they get dirty, when it rains or snows a lot, or when there is bad weather.
Soiling:When dust, dirt, or other particles build up on the surface of solar panels, they may not let as much sunshine reach the solar cells. Soiling can be worse in places that are dry and dusty or close to factories. Cleaning the solar panels can help with this problem, which will lead to more green energy being made.
Rain:Clouds that block the sun’s rays make it harder for solar panels to make energy, but rain can also improve their performance. Rainwater helps clean solar panels by washing away dust and dirt. Lightning can damage solar inverters, so protect them with a surge blocker and keep them out of the weather when you can.
Snow:Having snow on solar panels is a problem because it covers the surface and blocks some of the sun’s rays from hitting the cells. In places where it snows a lot, solar panels are often set up at an angle to help the snow slide off. According to local building rules and standards, PV panels are also made to last and can handle the weight of snow loads.In some cases, regular snow clearing may be needed to get things back to working at their best.
Flood Prone Areas:To make sure that solar panel systems work well and are safe in areas that are prone to floods, the wiring and tubing must be installed correctly. Electrical connections and parts can be made to be waterproof or can be put in protective cases. The route of the conduit is carefully planned to avoid areas that are likely to flood, and if needed, extra steps like higher mounts or flood barriers may be taken. To make sure they last a long time and work safely, solar panels installed in flood-prone areas should follow local building codes and rules.
References
Photovoltaic Energy Factsheet. (n.d.). Center for Sustainable Systems. https://css.umich.edu/publications/factsheets/energy/photovoltaic-energy-factsheet
Solar performance and efficiency. (n.d.). Energy.gov. https://www.energy.gov/eere/solar/solar-performance-and-efficiency
Solar Photovoltaic Cell Basics. (n.d.). Energy.gov. https://www.energy.gov/eere/solar/solar-photovoltaic-cell-basics
Lozanova, S. (2023, July 20). Solar Panel Durability And Performance In Extreme Weather Conditions. GreenLancer. https://www.greenlancer.com/post/solar-panel-durability-extreme-weather#:~:text=Solar%20panels%20are%20designed%20to,can%20affect%20solar%20electricity%20output.