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How does a Solar Cell Work?

A solar cell transforms sunlight into electricity through the photovoltaic effect. When light hits the cell, it excites electrons, creating an electric current. This clean energy source is revolutionizing power generation. Intrigued by how this simple yet profound technology harnesses the sun's power? Dive deeper to illuminate the science that's lighting our sustainable future. What will you discover next?
Michael Anissimov
Michael Anissimov
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.

Installing solar cells on a house will reduce its electricity usage.
Installing solar cells on a house will reduce its electricity usage.

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.

Solar cells use sunlight to generate power.
Solar cells use sunlight to generate power.

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.

Frequently Asked Questions

What is a solar cell and how does it generate electricity?

Solar cells produce direct current, which is converted into alternating current to power household appliances.
Solar cells produce direct current, which is converted into alternating current to power household appliances.

A solar cell, also known as a photovoltaic (PV) cell, converts sunlight directly into electricity through the photovoltaic effect. When photons from sunlight hit the solar cell, they knock electrons loose from atoms within the semiconductor material, typically silicon. This flow of electrons creates an electric current, which can be harnessed for power.

What materials are solar cells made of?

Solar panels use solar cells to generate power.
Solar panels use solar cells to generate power.

Solar cells are primarily made of silicon, a semiconductor that is abundant and has ideal electronic properties for PV applications. Silicon cells can be either monocrystalline, made from a single crystal, or polycrystalline, made from multiple crystals. Some thin-film solar cells use materials like cadmium telluride or copper indium gallium selenide.

How efficient are solar cells at converting sunlight into electricity?

A closeup of a solar panel.
A closeup of a solar panel.

The efficiency of solar cells varies depending on the material and technology used. As of 2023, typical commercial solar cells have efficiencies between 15% and 20%, according to the National Renewable Energy Laboratory (NREL). High-efficiency models can exceed 22%, while emerging technologies in the lab have demonstrated efficiencies over 40% under specific conditions.

Can solar cells produce electricity on cloudy days or at night?

Solar cells rely on sunlight for power.
Solar cells rely on sunlight for power.

Solar cells require sunlight to generate electricity, so their output decreases significantly on cloudy days and stops at night. However, they can still produce a small amount of power under diffuse light conditions. Energy storage systems can store excess energy generated during sunny periods for use when solar cells are not producing power.

What is the lifespan of a solar cell, and do they degrade over time?

Solar cells are designed to be long-lasting, with many manufacturers offering warranties of 25 years or more. Over time, solar cells do degrade, with an average annual degradation rate of about 0.5% for silicon PV cells, according to the International Energy Agency (IEA). This means after 25 years, many solar panels still operate at about 87.5% of their original efficiency.

How does the cost of solar cells compare to other forms of energy generation?

The cost of solar cells has plummeted over the past decades, making solar energy increasingly competitive with traditional energy sources. According to the International Renewable Energy Agency (IRENA), the cost of solar photovoltaics has dropped by 82% since 2010. This trend, combined with low operating costs and government incentives, makes solar a cost-effective option in many regions.

Michael Anissimov
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.

Learn more...
Michael Anissimov
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.

Learn more...

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Discussion Comments

selinalau

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.

anon282231

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?

wikesupply

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.

PelesTears

@ 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.

cougars

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.

wikesupply

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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    • Installing solar cells on a house will reduce its electricity usage.
      By: Alex Yeung
      Installing solar cells on a house will reduce its electricity usage.
    • Solar cells use sunlight to generate power.
      By: Ljupco Smokovski
      Solar cells use sunlight to generate power.
    • Solar cells produce direct current, which is converted into alternating current to power household appliances.
      By: creativenature.nl
      Solar cells produce direct current, which is converted into alternating current to power household appliances.
    • Solar panels use solar cells to generate power.
      By: Pinosub
      Solar panels use solar cells to generate power.
    • A closeup of a solar panel.
      By: Sergiogen
      A closeup of a solar panel.
    • Solar cells rely on sunlight for power.
      By: miiko
      Solar cells rely on sunlight for power.