A photovoltaic cell, more commonly called a solar cell, is an electronic device that turns the energy derived from light into electricity that can then be used by power sources. These cells are a kind of photoelectric cell which is defined as something that has electrical characteristics like voltage, a current or resistance which can vary when it is exposed to light. These solar cells are the main blocks of photovoltaic modules that are more commonly called solar panels.
Solar cells are called photovoltaic regardless of whether the light being delivered is artificial or natural sunlight. These are used as photodetectors, able to detect light or any other kind of electromagnetic radiation whose light density can be measured.
So, What is a Solar Cell and How Does it Operate?
In order for photovoltaic cells to operate, there are three basic things that the cells have to have:
- The ability to absorb light and generate either excitons or electron-hole pairs;
- The separation of the different kinds of charge carriers; and
- The separate extraction of such carriers to a circuit located externally
Conversely, a solar thermal collector gives heat by taking in sunlight. It does so with the aim of either heating something directly or causing indirect electrical power generation obtained from heat. On the other hand, a photoelectrolytic cell is a kind of photovoltaic cell that splits water into either oxygen or hydrogen using solar light. The photovoltaic effect was first shown by Edmond Becquerel, a French physicist, in the year 1839. He was 19 when he built the original photovoltaic cell in his father’s own lab.
How Are Solar Cells Made?
Silicon is the same thing that transistors in microchips are made with. Solar cells work in a similar style as these microchips. Silicon is a material that is known as a semiconductor. Some materials, which are more often than not metal, will allow electricity to move through them with ease, while other materials like wood and plastic, do not allow any flow of electricity to pass through them. These are called insulators, while the former are called conductors.
Semiconductors are neither of these things. They do not typically conduct electricity, but under some circumstances, they are able to. A solar cell sandwich has two layers of silicon that have been treated so that it can allow the flow of electricity. The lower level gets treated to ensure it has too few electrons, while the upper layer is treated so that it has just a few too many electronics. Placing these two layers over top of one another creates a barrier there and a joining of the two materials. No electrons are able to cross this barrier, but if the light is shone onto this barrier, light particles, or photons, go into that silicon sandwich. From there, the photons give up their energy to the atoms to conduct light.
How do Solar Cells Work?
These cells work because of a solar cell sandwiches p-type silicon, or red, and n-type silicon, or blue, together. It produces electricity by taking in sunlight and then makes electrons out of it. These electrons jump across the different flavors of silicon. When sunlight shines upon the cells, the light particles, called photons, cover the upper surface. The photons then carry that energy down throughout the cell. These photons pass over their energy to electrons in the lower layer, and the electrons take this energy and use it to bring said energy into the circuit to provide electricity. With the power flowing in the circuit, light and energy can be used.
Solar Cells in Space
The first time that a solar cell was used in a prominent manner was when they were put onto the Vanguard satellite. This satellite flew the cells in 1958 as a way to give the vehicle an alternate source of power outside of the main battery power bank. By giving additional cells to the exterior of the vehicle’s body, the mission time could go on much longer than what was once planned without any major changes being made to the power systems of the spacecraft or to the spacecraft itself. In the year 1959, the Explorer 6 was launched by the United States of America. It came with large, wing-shaped solar panels that have since become a common addition to satellites to this day. These arrays were made up of solar cells called 9600 Hoffman.
By the time that the 1960s rolled around, the main power source for most of the satellites currently orbiting Earth was and is solar cells. These also power other sorts of probes that are reaching deep into the solar system. This is because they are able to give the best power to rate ratio. That said, this success was only possible because when being applied in space, the costs of the power system could be exorbitantly high since space users did not have many other options for power. They were then, of course, willing to pay for the best cells that they could possibly get their hands on. The power market in space ended up driving up the need for the development of greater efficiency in solar cells. This happened up until the Research Applied to National Needs program found by the National Science Foundation began to develop solar cells that were specifically intended for applications right here on Earth.
Then, in the early years of the 1990s, the solar cell technology used for cells in space strayed away from the silicon technology that was used on panels here on earth. Instead, the spacecraft versions of solar panels used gallium arsenide-based III-V semiconductor materials. These eventually changed into the contemporary III-V multijunction photovoltaic cells that are currently being used on spacecraft.
Solar panels have come a long way from their humble beginnings and are now some of the most sought-after devices for space and terrestrial applications. With prices slowly dropping, most people may soon be able to take solar power into their own hands for uses as mundane and as common as residential applications.