What Are Solar Panels Made Of?

Solar panels look like simple rectangles of black glass, but they’re actually engineered from multiple layers of specialized materials, each serving a specific purpose. The composition is roughly 76% glass, 10% polymers, 8% aluminum, 5% silicon, and trace amounts of copper and silver. Understanding what’s inside helps explain why panels are durable, why they cost what they do, and how they convert sunlight into electricity year after year.

Modern solar panels are built to last 25+ years with minimal maintenance. This longevity comes from careful material selection and manufacturing processes. Silicon does the actual energy conversion, while glass, aluminum, and polymers provide protection, structure, and encapsulation. Knowing these materials also helps you understand recycling options when panels eventually reach end-of-life.

Key Takeaways

• Solar panels are made from silicon cells (the energy converter), tempered glass top layer, EVA encapsulant, aluminum frame, and backsheet materials
• Silicon accounts for only 5% of panel weight but does 100% of the electricity generation
• Tempered glass covers the cells and allows 90%+ of sunlight to pass through while protecting against hail and weather
• EVA (ethyl vinyl acetate) binds all layers together and is designed to remain flexible and transparent for 25 years
• The aluminum frame provides structural support and is fully recyclable
• Modern panels use silver busbars to collect electrical current from cells, and copper wiring for connections
• Panel materials are chosen to maximize efficiency, durability, and ease of manufacturing
• For professional solar installation tailored to your needs, call us free on (855) 427-0058

Silicon: The Energy-Generating Core

Silicon is the heart of every solar panel. This element does the actual work of converting photons from sunlight into electrons that flow as electrical current.

Silicon Type and Purity: Solar panels use silicon in two main forms. Monocrystalline silicon comes from a single pure crystal, giving electrons a clear path with minimal obstruction. Polycrystalline silicon is made by melting multiple silicon fragments together, creating grain boundaries that slow electron movement. Monocrystalline panels achieve 20-24% efficiency, while polycrystalline tops out around 15-18%. Today, nearly all residential and commercial panels use monocrystalline silicon because efficiency improvements have made manufacturing costs competitive.

How Silicon Works: Each silicon cell is a thin wafer, typically 180-210 micrometers thick (about the thickness of a postcard). The cell is treated with phosphorus on one side (creating a negative layer) and boron on the other (creating a positive layer). When photons hit the silicon, they knock electrons loose, creating a flow from the negative to the positive layer. This flow is electrical current.

Silicon Content by Weight: Despite doing all the work, silicon makes up only 5% of a panel’s weight. A 45-pound panel contains just 2-3 pounds of silicon. Glass and polymers add most of the weight because they’re needed in greater volume to protect and encapsulate the delicate silicon cells.

Recycling Silicon: Silicon is recyclable, though the process is complex. When a panel reaches end-of-life, silicon can be separated from glass and metal, but recycling is not yet cost-effective for most operations. This is changing as panel volumes increase and recycling technology matures.

Tempered Glass Top Layer

The top surface of every solar panel is tempered glass. This is the layer you see and can touch. Glass serves critical functions: protection, light transmission, and structural integrity.

Glass Thickness: Tempered glass on solar panels is typically 6-7 millimeters thick. This thickness is engineered to be strong enough to withstand hail, branches, and foot traffic from installers during maintenance, yet thin enough to keep weight down.

Light Transmission: The glass is designed to allow 90-95% of incoming sunlight to pass through. The remaining 5-10% is reflected away (which is why panels appear slightly reflective) or absorbed by the glass itself. Anti-reflective coatings on some premium panels reduce reflection to push transmission above 95%.

Tempered vs. Standard Glass: Standard window glass would shatter easily and create sharp fragments. Tempered glass is heated and cooled in a special process that creates surface compression. If broken, tempered glass crumbles into small granules rather than sharp shards—safer for installers and homeowners. This tempering process also makes the glass impact-resistant.

Weather Protection: The glass layer is the first line of defense against hail, rain, wind, salt spray, and ultraviolet radiation. In coastal areas where salt air is present, glass remains remarkably unaffected. UV rays degrade other materials over time, but glass is essentially immune to UV damage.

Photovoltaic Silicon Cells and Busbars

Beneath the glass lies the array of silicon cells, typically 60, 72, or more depending on panel size.

Cell Arrangement: In a standard 60-cell residential panel, cells are arranged in 6 rows of 10 cells each. Each cell is about 6 inches by 6 inches, so 60 cells cover a panel roughly 65 inches by 39 inches (with some spacing between cells). Cells are connected electrically in series, meaning current flows from one cell to the next, adding voltages together.

Busbars and Contact Ribbons: Each cell has metal busbars running across the surface to collect the electrical current. Early designs used 3 busbars, but modern panels use 4, 5, or even 12 busbars. More busbars mean shorter current paths, reducing resistance losses and generating slightly higher output. Each busbar is typically 0.3-0.5 millimeters wide and made of silver paste or silver-coated copper.

Silver Content: The busbars contain silver because silver is the best electrical conductor that doesn’t corrode. A typical 60-cell panel uses about 1-2 grams of silver. With millions of panels produced yearly, silver consumption for solar is significant. Some manufacturers are developing silver-free busbars to reduce material costs, but silver remains the industry standard.

Electrical Connections: Cells are interconnected with ribbon made of copper covered with tin. Copper is an excellent conductor, and tin prevents corrosion. These ribbons are soldered in place and must carry current reliably for 25 years without degrading.

EVA Encapsulant: The Adhesive Layer

Between the glass top and the cells, and between the cells and the backsheet, lies a layer of EVA (ethyl vinyl acetate), a type of plastic that acts as both adhesive and protective layer.

What EVA Does: EVA melts at approximately 150°C and can be laminated under heat and pressure to bond glass, cells, and backsheet into a single structural unit. It also prevents moisture from reaching the cells. When EVA cures (after lamination), it becomes a solid, clear material that is flexible yet durable.

Thickness and Properties: EVA layers are typically 0.5 millimeters thick on each side of the cell array. The material is transparent, so light passes through to the cells without significant loss. EVA must remain flexible for the panel’s lifetime—if it becomes brittle, it cracks, allowing moisture to infiltrate.

Durability Concerns: One of the most common failure modes in aged solar panels is EVA degradation or delamination, where the EVA layer separates from the glass or backsheet. This happens due to UV exposure, temperature cycling, or moisture ingress. Quality panels use stabilized EVA formulations that resist UV damage and remain flexible for 25+ years.

Cost Impact: EVA is inexpensive ($1-2 per kilogram), so it doesn’t significantly drive panel cost. However, using premium, UV-stable EVA formulations adds $20-50 to a panel’s manufacturing cost. Budget panels sometimes use lower-grade EVA, which can lead to degradation issues within 10-15 years.

Aluminum Frame and Junction Box

The aluminum frame provides structural support and mounting points. It’s one of the largest single components by volume.

Frame Design: The frame wraps around the panel’s perimeter and is typically anodized (an aluminum oxide coating) to prevent corrosion. The frame has grooves or channels on the backside to accept mounting hardware, allowing installers to secure the panel to roof racking without drilling. Frame depth is usually 30-35 millimeters.

Weight Distribution: The frame accounts for roughly 8% of a panel’s total weight. A 45-pound panel might have 3-4 pounds of aluminum. Aluminum is an excellent choice because it’s strong, lightweight, corrosion-resistant, and fully recyclable. Recycled aluminum is economically viable, so old panels can be melted down and reused.

Junction Box: On the backside of the panel, a small plastic box (the junction box) contains bypass diodes and wiring terminals. The junction box is where external wiring connects. It’s typically made of weatherproof plastic and rated for outdoor temperature extremes (-40°C to +85°C typical).

Bypass Diodes: Inside the junction box are bypass diodes that prevent current from flowing backward through a shaded cell. If one cell is shaded while others are in sunlight, a bypass diode allows current to bypass the shaded cell, avoiding hot-spot heating that could damage it. Most panels have one or two bypass diodes depending on design.

Backsheet Material: The Bottom Layer

The backsheet is the bottom surface of the panel, providing the final seal against moisture and electrical insulation.

Traditional Backsheets: Most backsheets are made from plastic laminates, often a combination of polyester, polyvinyl fluoride (PVF), or Tedlar (a DuPont trade name for PVF). These materials provide excellent UV resistance, moisture barriers, and electrical insulation. A typical backsheet is 0.3 millimeters thick.

White vs. Black: Some panels have white backsheets to reflect heat and keep the panel cooler. Others use black backsheets for aesthetic reasons. White backsheets can improve efficiency by 1-2% in hot climates, but the color choice is partly aesthetic.

Durability: The backsheet is exposed to the elements on the rear side (facing the roof). It must resist UV, ozone, temperature cycling, and moisture for 25 years. Low-cost backsheets sometimes degrade or yellow over time. Premium panels use multi-layer backsheets with superior UV stability.

Manufacturing Process and Material Integration

Understanding how these materials come together explains why panels are so durable.

Lamination: After silicon cells are soldered together with connecting ribbons, the cell string is sandwiched between a piece of glass and a piece of backsheet, with EVA layers on both sides. This sandwich is then placed in an industrial laminator, which heats and pressurizes the stack. Heat melts the EVA, causing it to flow slightly and bond all layers. Pressure keeps them in contact while EVA cures. This process takes about 20 minutes and is critical to panel longevity.

Framing: After lamination, the glass-cell-backsheet laminate is trimmed and an aluminum frame is glued and mechanically fastened around the edges. The frame ensures structural rigidity and provides mounting points.

Testing: Completed panels undergo electrical testing (IV curve testing) to verify output, and high-voltage testing to ensure electrical safety. Some panels are also subjected to accelerated life tests (thermal cycling, humidity cycling, UV exposure) to predict real-world durability.

New Materials on the Horizon

Material science continues to advance. Emerging technologies may introduce new materials to solar panels within the next 5-10 years.

Perovskite Layers: Perovskite is a semiconductor material that can be applied as a thin layer on top of silicon. Perovskite-silicon tandem panels promise efficiencies above 30-35%, compared to 20-22% for standard silicon. Perovskites are still being developed for durability and cost, but they may appear in commercial panels by 2027-2028.

Bifacial Panels: These panels have transparent backsheets that allow light to be captured from both sides. The rear side benefits from light reflected off the ground or nearby surfaces. Bifacial panels are already commercially available and add 10-20% more output in ideal installation scenarios (ground-mounted with bright ground reflectance).

Alternative Encapsulants: Researchers are developing encapsulant materials to replace EVA, including silicones and polyolefins that might offer better long-term stability and easier recyclability.

Summing Up

Solar panels are made from carefully selected materials, each serving a specific purpose. Silicon cells convert photons to electrons, tempered glass protects while transmitting light, EVA encapsulant bonds layers together and prevents moisture, aluminum frames provide structure, and backsheets seal the system. This multi-material composition is why panels are so durable—if any single material failed, the panel would degrade, but the combination creates a robust system rated for 25-30 years of reliable operation.

Material quality varies by manufacturer, and understanding composition helps you choose panels that will last. Panels from reputable makers that invest in quality EVA, UV-stable backsheets, and careful manufacturing will outperform budget alternatives, often by a significant margin over 20+ years of service.

For professional solar installation using quality, durable materials, call us free on (855) 427-0058 or get a free solar quote. Our installers will recommend systems built from proven materials matched to your climate and budget.

Updated May 2026