What Is a Solar Cell?
Solar cells, often referred to as photovoltaic (PV) cells, are electronic devices that convert light energy into electrical energy. They are usually connected in modules called solar panels or PV modules.
Solar panels produce direct-current (DC) electricity when exposed to sunlight.
Solar cell technology has been around since 1839 when William Grylls Adams and Richard Evans Day discovered that selenium produces electricity when exposed to light.
Solar cells have also been around since 1884 when Charles Fritts created a device that used gold-coated selenium wafers. His device was about 1% efficient, thus marking the beginning of solar cell technology as we know it today.
Solar cells were first used to provide electricity in the space program in the 1950s and 1960s. Solar cell structure solar cells, or photovoltaic (PV) cells, are electronic devices that convert light energy into electrical energy through a process called the photoelectric effect.
Development of Solar Cell Technology
Solar cell technology has evolved dramatically over the last few decades. Solar cell development gathered speed in the 1950s, but the first solar cells were expensive and inefficient.
Most cells were made from crystalline silicon, also used for microprocessors in computers, so scientists began to look for new ways to produce semiconductor material without using silicon.
The result was a much cheaper and more efficient solar cell. Solar cells only produce direct current (DC) electricity, so scientists also developed an inverter to transform the DC power into alternating current (AC).
Solar cell structures are made from silicon or other semiconductors that work together as P-N junctions. Silicon is the most common material used to create a solar cell.
Solar cells were first used commercially in satellites and as power sources on life rafts. Solar cell technology has also been used as a source of electricity on unmanned aerial vehicles (UAVs).
Solar Cell Structure
Solar cells are structured so that the light striking them can excite electrons. They are made out of silicon, a semiconducting material with four valence electrons that can bond with an electron from another atom (such as an excited electron), thus creating a hole in the structure.
Semiconductor Layer
This layer is built from a semiconductor material that does not conduct electricity under normal circumstances.
Solar cells are often made out of thin slices of crystalline silicon. Semiconductors are incredibly important for solar cell function because, without them, there would be no electron-hole pairs for excitation.
In addition to creating holes, semiconducting materials can also hold electrons. Solar cells have a layer of conducting material on top to allow the electrons to flow freely, creating an electrical current.
Layer of Conducting Material
On top of the semiconductor layer is a conducting material, typically a thin metal layer.
This layer creates a pathway for the electron-hole pairs to reach outside the solar cell. Solar cells without a conducting material on top cannot produce an electrical current.
Anti-Reflection Coating
A solar cell with no anti-reflection coating would reflect light toward the sun, and this light would not be used to excite electrons.
Anti-reflective coatings solve this problem by allowing light to pass into the semiconductor layer. Solar cells are designed with an anti-reflection coating on top of the metal layer to allow for maximum absorption of sunlight.
Types of Solar Cells
Solar cell structures vary in size and material, which affects the efficiency of converting sunlight into electricity.
Monocrystalline Silicon Cells
These types of solar cells are also called single-crystalline silicon cells. Solar cell manufacturers slice pure silicon into wafers and then treat the silicon to make p-type (positive) and n-type (negative) semiconductors.
The manufacturer slices the wafer very thinly, approximately 0.01 inches thick, and ingots are cut from the wafer. These ingots are about 1 inch in diameter and can measure several feet.
Polycrystalline Silicon Cells
Solar cell manufacturers alloy the silicon into small crystals, or polycrystals, which aids charge carriers’ movement due to a smaller distance between positive and negative charges.
Manufacturers use molten silicon to make these cells, which is easier than slicing the silicon wafer. Solar cell manufacturers space out the polycrystalline structure with a boron solution to help control electrical conductivity.
Thin-Film Cells
The size of solar cells can make them fragile and inflexible, so manufacturers have begun experimenting with different and more flexible solar cell materials. Solar cells made from thin films can be cheaper and lighter than conventional semiconductor-based cells.
Manufacturers create thin-film solar cells with physical vapor deposition in a process that coats the surface of an object with a thin layer of material by putting it in a vacuum and heating the material.
High-Efficiency Cells
High-efficiency photovoltaic cells are typically made from III-V compound semiconductors, such as gallium arsenide (GaAs), instead of silicon.
These solar cells are the most efficient but expensive and tricky to produce in large quantities. Solar cell manufacturers can only create these types of cells in small batches due to the complexity and expense of the process.
Usage of Solar Cells
Solar cells have many different applications.
Solar Panels
Solar panels produce electricity by allowing sunlight to hit solar cells. Solar cells turn the energy of photons into electrical energy. Solar cell materials work with the sunlight spectrum to absorb this high-energy light and convert it into usable power.
Charge Batteries
Solar cells can charge electrical devices during the day to make them usable at night.
Solar cells are often present in small handheld gadgets like cell phones and MP3 players, but more substantial applications include solar panels on top of buildings or light poles.
Power Generation
Solar cells can also be used in solar power generating systems in remote locations where it would be expensive to provide an alternative source of electricity.
Solar cells are also being adapted to create solar-powered vehicles, which would not require an external source of electricity. These vehicles have solar panels on the roof and sides that absorb sunlight and power the motor.
Spacecraft Electrical Energy
Solar cells are also commonly used on solar-powered spacecraft, which are satellites that use the sun's energy for power.
Benefits and Drawbacks of Solar Cells
Solar cells have several benefits, such as:
- Solar cells are an inexhaustible source of clean energy.
- They can power remote locations.
- They reduce reliance on fossil fuels.
- Solar cells save money over time.
- They have a low carbon footprint.
- Solar cell technology is constantly improving.
Drawbacks of solar cells include:
- It takes lots of space to create a solar farm.
- The materials used to create solar cells are expensive.
- They are only efficient when the sun is shining.
Key Takeaways
Solar cells are produced by collecting free electrons created when sunlight strikes the atoms of the solar cell material. Solar cells excite the free electrons, which interrupts their flow path through the cell to conduct electricity.
Solar cells can be made of different materials and designed into various forms due to their convenience and efficiency.
Solar cells have plenty of limitations, but the cells are constantly being improved. Solar cells provide a unique opportunity for an inexhaustible source of clean energy, but more research and development is required to improve the cells’ efficiency.
FAQs
1. What is a solar cell?
Solar cells are devices that convert energy from sunlight into electricity. They are made out of non-conducting materials in which electrons can flow freely.
2. How is a solar cell used?
Solar cells are usually connected to form a solar panel used by solar farms. Solar farms collect solar energy from large arrays of solar panels and direct it to a solar inverter.
3. How does a solar cell work?
The atoms of the solar cell material receive sunlight, or photons, that excite the solar cell to conduct electricity.
4. How is a solar cell made?
The first solar cells were created in the 1800s, but it was not until 1954 that solar cells became commercially available. The first solar cells were made of crystalline silicon, which was an energy-intensive process. Solar cells are now made of thin films, which are cheaper and easier to produce.
5. What material (or combination of materials) is used for solar cells?
Most solar cells are made out of silicon but can also be made out of gallium arsenide (GaAs).
