What Are Solar Panels Made Of?

Team electrician installing solar panels working on alternative energy sources clean.
Visoot Uthairam / Getty Images

Solar panels are made of individual solar cells that are connected together to make a panel or module. The solar cells themselves contain a semiconductor in charge of creating electricity in the presence of sunlight. Other components of a solar panel include metal, glass, and different types of plastics.

While some of the materials may differ depending on the type of solar panel and its use, the basic components that absorb and reflect sunlight, move current, and hold the panel together must all be present to safely and efficiently produce electricity. 

Photovoltaic Cells

The photovoltaic (PV) effect is the process that allows solar panels to convert sunlight into usable electricity. It was first observed in 1839 by a French physicist named Alexandre-Edmond Becquerel. The modern PV cell, also known as solar cell, was patented in 1946. These solar cells were the first to successfully use silicon with impurities to create the electrical resistance needed for solar cells to work properly.

Silicon crystal with photovoltaic cells
Silicon crystal with photovoltaic cells.

WLADIMIR BULGAR / Getty Images

A variety of materials can be used as the semiconductor in a solar cell. Each has unique properties that make it more or less attractive for the mass manufacturing of solar panels. 

Monocrystalline Silicon

Silicon is a non-metal element that is considered a semiconductor because it conducts more electricity than an insulator but not as much as a metal. Solar cells made from monocrystalline silicon are considered first-generation solar cells. They are made by slicing pure silicon crystals from large ingots.

These ingots are most commonly formed using the Czochralski method of silicon crystallization. During this process, a seed crystal is attached to the end of a rod and lowered onto the surface of molten silicon. This silicon is often mixed with boron. The rod is then slowly extracted again, and while it is being lifted from the crucible, both the rod and the crucible are rotated in opposite directions. The ingot slowly forms and is then sliced into thin, single-crystal wafers which can then be layered with phosphorus and used in solar cells.

Monocrystalline solar cells have a higher cost than polycrystalline solar cells, but have higher efficiency, especially when perpendicular to sunlight.    

Polycrystalline Silicon

This material is made of non-aligned silicon crystals created by melting many silicon crystals together. Because electrons must travel through multiple crystals instead of just one, the efficiency of polycrystalline solar cells is lower than monocrystalline. They have the advantage of being significantly less expensive than monocrystalline silicon semiconductors, so they are relatively common.

Hydrogenated Amorphous Silicon

Used in thin-film silicon solar cells, hydrogenated amorphous silicon is a material deposited as a thin layer on a variety of substrates like glass, stainless steel, and plastics. This type of solar cell is considered second-generation and has definite advantages over first-generation mono- and polycrystalline silicon solar cells.

They are relatively cheap to produce since they do not use a lot of material. They can be used to make very small solar cells and are also more environmentally friendly than some other types of solar cells because they avoid using toxic heavy metals. However, because they are made of such thin layers, not as much solar radiation can be absorbed, which makes them much less efficient than other types of solar cells.

Cadmium Telluride

Another second-generation solar technology is cadmium telluride, made of the metal cadmium and metalloid telluride, which exhibits properties of both metals and non-metals. It has relatively high efficiency because it is able to use a broader wavelength of light to produce electricity than silicon solar cells. Cadmium is a byproduct of other materials, so its abundance makes it cheap to use in solar cells.

Unfortunately, the use of cadmium telluride solar cells has an environmental cost. Cadmium alone is a highly toxic material, and cadmium and telluride together also exhibit toxicity. Several studies have shown that the toxic metals have leached from solar cells and that the leachate exceeded several legal limits for metals in drinking water and soil. Even so, they remain a popular option for solar cells. 

Copper Indium Gallium Diselenide

Copper indium gallium diselenide (CIGS) is another metallic material used in thin-film PV cells. It is a semiconductor that improves upon copper indium diselenide technology by adding gallium to increase the efficiency of the cell.

Producing CIGS solar cells takes less energy than making silicon solar cells, and they are also incredibly lightweight and flexible. This is why they are the second most common semiconductor material after silicon.

When CIGS was tested for leachate toxicity, several of the metal concentrations in the leachate exceeded World Health Organization drinking water limits. However, newer research out of the University of Tokyo has shown promising data on the recycling of CIGS leachate and the possibility of recovering a high percentage of the original metals used in the solar cells.

Perovskite

This family of materials has an energy conversion efficiency of 25%. They are named after the mineral perovskite because of their similar crystal structure. The major concern over the adoption of these materials to manufacture solar cells is the use of a lead-based absorber which is highly toxic if released into the environment. There are currently other materials that are being tested that may eliminate the need for lead in perovskite solar cells. 

Other Panel Materials

Cross section view showing parts of solar panel with names on white background
Many layers make up a functioning solar panel.

alejomiranda / Getty Images

There are a number of other components that make up a solar panel. Each one plays a role in protecting the solar cells from the elements, moving the electricity efficiently through the system, or keeping the electrical components operating properly. While some elements may differ depending on the design or use, these are the most common parts of a solar panel.

Glass

Glass is often used to coat the solar panel to keep the cells from being damaged. It is low-iron and non-reflective to allow for maximum absorption of sunlight.

Encapsulant

Solar cell encapsulants are used to bond layers of the solar cell together. Ethylene vinyl acetate (EVA) is used in almost 80% of solar cells. It is inexpensive, allows light to travel through it easily, and has high adhesive strength, which is why it is so popular. 

Rear Surface

In solar panels that only absorb light on one side, a rear surface sheet or backing is placed behind the grouping of cells to reduce the temperature of the solar panel. This backsheet is usually made from polymers, namely polyvinyl fluoride (PVF) or polyethylene terephthalate combined with PVF.

Junction Box

Junction boxes on the backs of solar panels encase the copper wiring that contains the electricity produced by the solar cells. It contains junction diodes that keep electricity flowing in one direction so it does not go back into the panel.

Aluminum Frame

Solar cells that are wired together make up a solar panel. The cells are placed in an aluminum frame that protects the entire panel and keeps water and dust from entering the enclosure. After silicon, aluminum is the second most common metal found on Earth. It is a lightweight metal that is resistant to the elements, making it an ideal choice for solar panel frames.