Most solar panels are made of silicon solar cells, tempered glass, polymer encapsulant, an aluminum frame, copper wiring and a plastic junction box. The silicon cells convert sunlight into electricity. The glass, polymers and frame protect those cells from weather and physical damage.
Solar Panel Materials at a Glance
| Solar panel component | Common material | Purpose |
|---|---|---|
| Front surface | Tempered glass | Protects the cells and lets sunlight through |
| Solar cells | Crystalline silicon | Converts sunlight into direct-current electricity |
| Electrical contacts | Silver and copper | Collects and carries electricity |
| Encapsulant | Polymer, often EVA or a similar material | Seals the cells against moisture |
| Back layer | Polymer backsheet or glass | Protects the rear of the panel |
| Frame | Aluminum | Provides strength and mounting support |
| Junction box | Plastic, copper and electronic components | Connects the panel to cables and protects electrical connections |
| Cables and connectors | Copper and plastic | Transfers electricity between the panels and inverter |
What Are the Main Parts of a Silicon Solar Panel?
A standard silicon solar panel combines semiconductor cells with protective glass, polymer layers, metal wiring and an aluminum frame.
1. Silicon Solar Cells
Silicon is the main semiconductor used in most solar panels. Manufacturers refine silicon from high-grade quartz, form it into ingots, slice the ingots into thin wafers and process those wafers into photovoltaic cells.
The two main forms of crystalline silicon are:
- Monocrystalline silicon: Each cell is made from a single crystal structure. These cells generally provide higher efficiency.
- Polycrystalline silicon: Each cell contains multiple silicon crystal structures. This process was historically less expensive, although polycrystalline panels are less common in newer installations.
The cells also contain small amounts of conductive metals. Silver is commonly used for contacts on the cell, while copper ribbons connect the cells inside the module.
2. Tempered Glass
The front of a standard solar panel is made from strong, transparent glass. It lets sunlight reach the cells and protects them from rain, hail, wind and temperature changes.
Glass makes up most of the weight of a typical panel. It accounts for approximately 75% of the weight in the crystalline-silicon panels described by the U.S. Environmental Protection Agency.
3. Polymer Encapsulant
Solar cells sit between layers of plastic encapsulant. This material holds the cells in place and helps keep moisture away from the electrical components.
Manufacturers laminate the glass, encapsulant and cells together with heat. The finished layer protects the cells while allowing sunlight to pass through.
4. Backsheet or Rear Glass
Many traditional panels have a polymer backsheet on the rear. It provides electrical insulation and helps protect the cells from moisture and physical damage.
Some newer panels use glass on both sides instead of a polymer backsheet. These are commonly called glass-glass solar panels. Their construction varies by manufacturer.
5. Aluminum Frame
An aluminum frame surrounds most rooftop solar panels. It reinforces the module, protects its edges and provides attachment points for mounting hardware.
Aluminum is also one of the easier materials to recover during recycling. Glass, aluminum and copper can generally be separated more easily than the bonded polymer layers and solar cells.
6. Junction Box, Cables and Connectors
A plastic junction box is attached to the back of the panel. It contains electrical connections and bypass diodes, which help manage current flow when part of the panel is shaded.
Copper cables and connectors carry the panel's direct-current electricity to other panels and then to an inverter. The inverter changes direct current into alternating current for household use or the electrical grid.
Are All Solar Panels Made From Silicon?
No. Most solar panels use crystalline silicon, but thin-film panels use other semiconductor materials.
Thin-Film Solar Panels
Thin-film photovoltaic cells use very thin semiconductor layers placed on a supporting material such as glass, plastic or metal. Common thin-film technologies include:
- Cadmium telluride, or CdTe
- Copper indium gallium diselenide, or CIGS
- Amorphous silicon
CdTe panels commonly use glass as both a supporting surface and part of the protective structure. CIGS panels contain copper, indium, gallium and selenium in their light-absorbing layer.
Thin-film panels make up a smaller share of the market than crystalline-silicon panels. Their materials and recycling processes also differ from those used for conventional silicon modules.
Do Solar Panels Contain Toxic Materials?
Some solar panels contain small amounts of metals such as lead or cadmium, depending on the cell technology, solder and other components. The amount varies by panel model and manufacturer.
The EPA states that some discarded solar panels may qualify as hazardous waste under certain testing conditions, while others may not.
This does not mean a properly installed panel is dangerous during normal use. Old or damaged panels should be sent through appropriate reuse, recycling or waste-management channels rather than dismantled casually.
What Happens to the Materials When a Panel Is Recycled?
Solar panel recycling usually starts with removing the aluminum frame and junction box. Recyclers then separate the glass from the silicon cells through mechanical, thermal or chemical processes.
Glass, aluminum and copper are generally the easiest materials to recover. Separating silicon, polymers and small amounts of specialty metals is more complex.
Bottom Line
A conventional solar panel is a glass-and-silicon module with an aluminum frame, polymer sealing layers, silver contacts, copper wiring and a junction box. Thin-film panels use other semiconductor materials, especially cadmium telluride or copper indium gallium diselenide, but they still commonly include glass, polymers, metals and protective electrical components.