How does a Solar Cell Work?
Michael Anissimov
Michael Anissimov
There are a variety of different devices that use sunlight to generate power, but the basic way that a solar cell works is the same. In a photovoltaic (PV) cell, there are two layers of silicon, both of which are doped, or lightly mixed, with a certain element. Typically, one side is doped with boron and the other with arsenic.
Because of the way each element bonds to the silicon, the layer containing boron, called the n-type layer, has a surplus of free electrons. The other side, the p-type layer, has a deficit of electrons, called holes. The p-type layer and n-type layer are pressed closely against each other and linked by a wire connected to an external load. This creates a circuit in the solar cell.
When sunlight of the right energy level hits the n-type layer, which is on top, it excites some of the free electrons, which break loose from their natural state — pairs — and flow across the boundary between the layers to create a current. This only works if the two layers of the cell are pressed directly into each other. This is usually accomplished by fabricating both sides as part of the same process.
The current flows through the p-layer into the wire, which goes to the load, generally used to store electricity. Direct current (DC) is produced. If alternating current (AC) for household appliances is desired, the DC current is put through an alternator.
After flowing through the load, the current continues back into the n-layer, which is lacking in electrons in some areas due to the current. The process continues. A current is generated without any mechanical input. Unfortunately, the materials used to make solar cells can be quite expensive.
For protection, the top layer of the solar cell is covered with a glass plate affixed with transparent resin. The entire setup is called a p-n junction diode. More sophisticated cells use a series of p-n junction diodes.
The first solar cells were only 1% efficient. Today, commercial solar panels are between 5% and 15% efficient. There are currently millions of dollars going into research on improving these percentages.
Michael Anissimov
Michael is a longtime TheSolarPanelGuide contributor who specializes in topics relating to paleontology, physics, biology, astronomy, chemistry, and futurism. In addition to being an avid blogger, Michael is particularly passionate about stem cell research, regenerative medicine, and life extension therapies. He has also worked for the Methuselah Foundation, the Singularity Institute for Artificial Intelligence, and the Lifeboat Foundation.
Michael Anissimov
Michael is a longtime TheSolarPanelGuide contributor who specializes in topics relating to paleontology, physics, biology, astronomy, chemistry, and futurism. In addition to being an avid blogger, Michael is particularly passionate about stem cell research, regenerative medicine, and life extension therapies. He has also worked for the Methuselah Foundation, the Singularity Institute for Artificial Intelligence, and the Lifeboat Foundation.
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Discussion Comments
Currently major progress is being made. Most commercial solar panels can reach efficiency above 20%, which make solar energy utilization more popular and better solution. Solar lights are increasingly used for home and garden as a way of living green.
What is the role of a depletion zone in a solar cell? I mean, what happens to the depletion zone in the pn junction when photons strike it?
I have been working on solar panel products for over two years, but before I read this article, I really didn't know how the solar cells generated electricity.
@ Cougars- The silicon based solar cells that are so common today have only been around since the early fifties. These cells were produced initially for space missions to power satellites, space ships and the likes. Their value soon became evident, and they were soon adopted by the general public once the price started to come down.
There is a new photovoltaic solar technology on the horizon, which may prove to be more efficient than flat silicon panels. Most home installs are not sun tracking, so they are most efficient when the sun is directly overhead, residential tracking systems can also be somewhat cost prohibitive, and often times HOAs and Covenants do not allow tracking systems. A few companies are working on systems that use Cadmium, Indium, Gallium, and diselenide to create panels comprised of tubes filled with photovoltaic materials. These systems can increase overall efficiency because they allow for peak absorption of solar radiation at multiple angles, extending the peak production times of the system. These systems look similar, but instead of individual cells, the panels look like they are holding a number of black, fluorescent light bulb like, tubes.
How long has photovoltaic solar cell technology been available? Is photovoltaic solar technology a fairly new concept or has it been around for a while? I am in need of information on the history of solar power generation and I would appreciate it if someone could help me out. Thanks to anyone out there who knows.
There are two sizes of solar cells: 125x125mm and 156x156mm. Each piece is rated power is 2.5W and 3.9W. For high quality solar cells, look for
10 years Peak Power Warranty - 90 percent minimum peak power or 20 years Peak Power Warranty - 80 percent minimum peak power.
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