What Are Photovoltaic Cells (PV) and How Do They Work?

What Are Photovoltaic Cells (PV)

Photovoltaic (PV) cells, also called solar cells, are the technology that allows solar panels to convert sunlight into electricity. When sunlight reaches a PV cell, energy from the light activates electrons within a semiconductor material, creating an electrical current. This process is known as the photovoltaic effect.

Multiple photovoltaic cells are connected to form a solar panel, and several panels can work together to generate electricity for a home or business. Most modern solar panels use silicon-based PV cells because of their efficiency, durability, and widespread availability.

Understanding how photovoltaic cells work can help homeowners better understand solar panel performance, efficiency, and the technology behind residential solar energy systems.

How Do Photovoltaic Cells Work?

Photovoltaic cells generate electricity by converting sunlight into electrical energy through the photovoltaic effect. Here’s how the process works:

1. Sunlight reaches the solar cells. Solar panels contain photovoltaic cells made from semiconductor materials, most commonly silicon.
2. The cells absorb light energy. Photons from sunlight transfer energy to electrons within the semiconductor.
3. An electrical current is generated. The cell’s internal electric field helps separate electrical charges, allowing current to flow through an external circuit.
4. Solar panels produce direct-current electricity. Multiple PV cells work together within a solar panel to generate direct-current (DC) electricity.
5. An inverter converts the electricity. A solar inverter converts DC electricity into alternating-current (AC) electricity that can power household appliances.

This process allows residential solar systems to generate electricity whenever sufficient sunlight reaches the panels.

Types of PV Cells

Manufacturers can create photovoltaic cells in various ways using different materials. Silicon (Si) is the most popular material for making commercial solar cells, but others like Gallium Arsenide (GaAs), Cadmium Telluride (CdTe), and Copper Indium Gallium Selenide (CIGS) are also used. Depending on the material, solar cells can either be brittle crystalline structures, such as Si and GaAs, or flexible thin-film cells, like Si, CdTe, and CIGS. We can further divide crystalline solar cells into monocrystalline and polycrystalline, as figure 4 illustrates. Monocrystalline PV cells consist of a single, uniform crystal lattice, while polycrystalline cells feature a mix of different crystal structures. Additionally, solar cells vary by the number of layers or “p-n junctions” they have. While most commercial PV cells are single-junction, manufacturers have also developed multi-junction PV cells that offer higher efficiencies but at a higher cost.

New Developments in Photovoltaic Cell Technology

Photovoltaic technology continues to evolve as manufacturers develop ways to improve solar cell efficiency, durability, and electricity production.

Several important developments include:

• TOPCon Solar Cells: Tunnel Oxide Passivated Contact (TOPCon) technology reduces certain electrical losses within silicon solar cells, helping improve energy conversion efficiency. It is used in many modern high-efficiency solar panels.
• Heterojunction (HJT) Solar Cells: Heterojunction technology combines crystalline silicon with thin layers of other silicon materials to improve electrical performance and reduce certain energy losses.
• Perovskite Solar Cells: Perovskites are an emerging class of photovoltaic materials that have demonstrated significant efficiency improvements in laboratory research. Researchers continue working to improve their durability and commercial scalability.
• Tandem Solar Cells: Tandem cells combine multiple light-absorbing materials to capture a broader portion of the solar spectrum. Silicon-perovskite tandem technology is one promising approach being researched to achieve higher efficiencies.

For homeowners, these advances help explain why solar panel performance continues to improve. However, the newest technology is not automatically the best option for every installation. Product availability, proven reliability, warranty coverage, and total system cost remain important considerations.

The Different Layers of a PV Cell

A photovoltaic (PV) cell consists of multiple layers, each playing a critical role in converting sunlight into electricity. The most common and crucial layers include:

1. Protective Glass Layer: This top layer protects the cell from environmental elements while allowing sunlight to pass through.
2. Anti-Reflective Coating: Applied to the surface of the cell, this layer reduces light reflection and ensures more light is absorbed rather than reflected away.
3. N-Type Semiconductor Layer: This layer is doped with materials that add extra electrons, creating a negative charge.
4. P-Type Semiconductor Layer: Positioned below the N-type layer, this layer is doped to have fewer electrons, creating spaces known as “holes,” resulting in a positive charge.
5. Junction Layer: The area where the N-type and P-type layers meet is called the junction. Here, the movement of electrons from the N-type to the P-type layer creates an electric field.
6. Back Contact Layer: This layer acts as the back electrode, providing a pathway for electrons to flow out of the cell and into an external circuit before returning to the cell.
7. Front Contact Layer: Often made of fine metal fingers, this layer collects and transfers the electrons from the semiconductor to the external circuit.

These layers work together to capture sunlight, generate electrical charges, and then transport these charges, creating an electrical current.

What is the Photovoltaic Effect?

The photovoltaic effect is a phenomenon that occurs when a photovoltaic cell, exposed to sunlight, generates voltage or electric current. Inside these solar cells, there are two distinct types of semiconductors: the p-type and the n-type. These semiconductors come together to form a p-n junction. At this junction, an electric field emerges as electrons migrate towards the p-side, which is positive, and holes shift towards the n-side, which is negative. This field directs negatively charged particles in one direction and positively charged particles in the opposite direction.

Sunlight consists of photons, small packets of electromagnetic energy. When these photons with the right wavelength hit the solar cells, they transfer their energy to an electron in the semiconductor material. This energy boost propels the electron into a higher energy state, known as the conduction band. Once in the conduction band, electrons can freely move across the material. It’s this movement of electrons that generates an electric current in the cell.

What Is the Difference Between a Photovoltaic Cell and a Solar Panel?

A photovoltaic cell is an individual component that converts sunlight into electricity, while a solar panel contains multiple photovoltaic cells connected together.

Because a single PV cell produces a relatively small amount of power, manufacturers combine cells into larger modules, commonly called solar panels. Multiple solar panels can then be connected to form a solar array.

Component	Function
Photovoltaic cell	Converts sunlight into electrical energy
Solar panel	Combines multiple PV cells into one module
Solar array	Connects multiple solar panels to generate more electricity
Solar energy system	Includes panels, inverters, mounting equipment, wiring, and other components

For residential installations, solar panels work together with an inverter and other electrical equipment to supply usable electricity to the home.

To learn more about the different technologies used in solar panels, explore our guide to the types of solar panels.

Photovoltaic Cells and Solar Efficiency

Designing efficient photovoltaic (PV) cells is challenging due to several factors that limit their performance. A primary limitation is that a quarter of the solar energy reaching Earth cannot be converted into electricity by silicon semiconductors. This is because semiconductors need a minimum amount of energy, known as the band-gap energy, to dislodge an electron from the crystal structure. For silicon, this band-gap energy is 1.12 electron volts. Since sunlight contains photons with a wide range of energies, not all photons have enough energy to displace an electron in a silicon PV cell. Moreover, any photon energy exceeding the band-gap energy converts into heat, which further reduces efficiency because this heat is not utilized for generating electricity.

Additionally, not every electron that becomes available contributes to electricity production. Some electrons do not gain enough momentum from the semiconductor’s internal voltage to exit the system. These factors lead to a theoretical efficiency limit of about 33% for silicon PV cells.

To enhance PV cell efficiency, various methods can be employed, each adding to the cost. These methods include improving the semiconductor’s purity, using more efficient materials like Gallium Arsenide, adding more layers or p-n junctions to the cell, or concentrating sunlight with concentrated photovoltaics. However, PV cells also experience degradation over time, losing efficiency due to factors like UV exposure and weather cycles. The National Renewable Energy Laboratory (NREL) reports that the average rate of efficiency loss is 0.5% per year.

Why Does Photovoltaic Cell Efficiency Matter for Homeowners?

Photovoltaic cell efficiency measures how effectively a solar cell converts incoming sunlight into electricity. Higher-efficiency cells can generate more electrical power from the same amount of sunlight under comparable conditions.

For homeowners, solar panel efficiency can affect:

• Roof Space: Higher-efficiency panels can generate more power within a limited installation area.
• System Size: More efficient panels may help homeowners reach their desired system capacity using fewer panels.
• Energy Production: Solar electricity generation depends on panel efficiency as well as sunlight availability, temperature, shading, and system design.
• Long-Term Value: A panel’s efficiency should be considered alongside its cost, warranty, and expected performance over time.

Although efficiency is important, the most efficient solar panel is not always the most cost-effective choice. A properly designed solar installation balances panel performance with the property’s conditions and the homeowner’s energy goals.

Frequently Asked Questions About Photovoltaic Cells

Do photovoltaic cells work on cloudy days?

Yes. Photovoltaic cells can generate electricity using sunlight that reaches them through cloud cover. However, solar panel output is generally lower during cloudy conditions because less sunlight reaches the cells.

What are photovoltaic cells made of?

Most commercially available photovoltaic cells are made from silicon, a semiconductor material that converts sunlight into electricity. Other photovoltaic materials include cadmium telluride (CdTe), copper indium gallium diselenide (CIGS), and emerging perovskite materials.

How long do photovoltaic cells last?

Many silicon solar panels are designed to operate for 25 years or longer. Their electricity production gradually declines over time, but the rate depends on the technology, manufacturing quality, and environmental conditions.

Are You Ready for PV Solar Panels?

Are you ready to harness the power of the sun and transform your home into a beacon of sustainability and efficiency? 8MSolar presents an opportunity for you to join the renewable energy revolution with our state-of-the-art photovoltaic (PV) solar panels.

Why choose solar panels for your home? The reasons are compelling:

1. Reduce Your Energy Bills: Solar power can significantly lower your monthly energy costs. With 8MSolar’s help, you’ll generate your own electricity, relying less on the grid and more on the abundant energy provided by the sun.
2. Increase Your Property Value: Homes equipped with solar energy systems often see a rise in property value, making solar panels a wise investment for the future.
3. Environmentally Friendly: By choosing solar energy, you’re opting for a clean, green source of power. Solar panels produce electricity without emitting harmful pollutants, reducing your carbon footprint and contributing to a healthier planet.
4. Energy Independence: With 8MSolar, you’ll tap into the freedom of producing your own energy. This means less dependence on utility companies and protection against rising energy costs.
5. Reliability and Low Maintenance: Our solar panels are designed to withstand the elements and provide reliable energy production with minimal maintenance required. Enjoy peace of mind knowing that your solar system will keep your home powered for years to come.
6. Tailored Solutions: At 8MSolar, we understand that every home is unique. That’s why we offer customized solar solutions designed to meet your specific energy needs and preferences.
7. Expert Support: From the initial consultation to installation and beyond, our team of experts will guide you every step of the way. We’re committed to ensuring a smooth transition to solar energy for your home.
8. Incentives and Rebates: Take advantage of federal, state, and local incentives that make switching to solar more affordable than ever. Our team will help you navigate these opportunities to maximize your savings.

Embrace the future of home energy with 8MSolar. Contact us today to learn how easy and beneficial it is to make the switch to solar power. Or if you are testing the waters, give our Virginia and North Carolina solar calculator a try. Together, we can light up your home with clean, sustainable, and cost-effective energy. Let’s power your tomorrow, today.