How Are Solar Panels Made? (2024) – MarketWatch

Most solar PV modules use silicon solar cells, which you can classify into two main types: monocrystalline and polycrystalline. Both types of PV cells are made of high-purity silicon but have different manufacturing processes:

• Monocrystalline solar cells get cut from single crystals. The crystals are grown from molten silicon through a highly controlled process.
• Manufacturers make polycrystalline cells by merging multiple crystals together. As a result, this process does not require growing a single crystal from molten silicon.

Monocrystalline solar panels can convert sunlight into electricity more efficiently but are more complex and expensive. Polycrystalline solar panels are easier to make and more affordable but have a lower efficiency.

The technical details of solar panel manufacturing are complex, but we break down each step in the process in the following sections. The steps below apply to crystalline silicon solar panels, which represent over 90% of the global market share. Other panel types, including thin-film panels, have different manufacturing processes depending on the material.

• Silicon Extraction and Refining

According to the Royal Society of Chemistry, silicon is one of the most abundant elements on Earth, making up 27.7% of the planet’s crust. However, naturally occurring silicon is combined with other elements such as oxygen, phosphorus and nitrogen. Manufacturers must process these raw materials to obtain the pure silicon required to make solar panels.

The oxygen content of mineral silica can be removed with high temperatures, which results in high-purity silicon. The solar industry uses 99.9999% pure polysilicon to manufacture both polycrystalline and monocrystalline solar cells.

• Silicon Wafer Production

Poly cells have a more straightforward production process that involves casting and cutting polycrystalline silicon blocks into the square wafers used to make PV cells.

Making mono cells is more complex since solar manufacturers must first ensure the molten silicon solidifies into a single crystal. The process relies on the Czochralski method, in which crystals are “grown” by dipping a smaller “seed crystal” in molten silicon. The result is a large cylindrical block made of a single silicon crystal that manufacturers can cut into solar cells.

• Photovoltaic cell manufacturing

Manufacturers can improve the efficiency of PV cells by adding controlled amounts of boron and phosphorus. Solar panel efficiency measures the amount of sunlight a solar cell can convert into energy.

The added elements act as semiconductors — phosphorus results in n-type silicon, while boron results in p-type silicon.

• N-type semiconductors have a larger number of free electrons, which carry a negative charge when moving.
• P-type semiconductors have “electron holes,” which carry a net positive charge.
• P-type and n-type silicon are layered into a “PN junction,” which is the basic principle of a solar cell.
• When exposed to a light source, the electrons in n-type silicon gain energy, moving towards the “holes” in the p-type silicon to create an electric current.

In other words, this process converts sunlight into electric power.

Solar panels consist of multiple PV cells connected together using silver conductors and copper solder. There are many panel sizes, but most residential solar panels have 60 or 72 cells. Some manufacturers make solar panels with 120 or 144 half-cells, which have roughly the same dimensions as 60 and 72-cell panels.

• Encapsulation and Backsheet

Manufacturers cover the PV cells with an anti-reflective coating to increase sunlight absorption. Solar panels are also encapsulated by two layers of ethylene vinyl acetate (EVA), which helps to protect the panels from dust and humidity. The final assembly includes covering the panel with a frontal tempered glass sheet and polymer backsheet.