What are photovoltaic cells made of?

Photovoltaic cells, also known as solar cells, are devices that convert sunlight into electricity. They have become increasingly popular in recent years as a means of generating renewable energy. In the United Kingdom, solar power is one of the fastest-growing sources of renewable energy, with over 11 GW of installed capacity in 2019. But what are photovoltaic cells made of, and how do they work?

Photovoltaic cells are made of semiconducting materials, which are materials that have properties between those of conductors (such as metals) and insulators (such as glass). The most commonly used semiconducting materials in photovoltaic cells are silicon, cadmium telluride, and copper indium gallium selenide.

Silicon is the most widely used material in photovoltaic cells because it is abundant, non-toxic, and has good electrical properties. Silicon is a crystalline material that is doped with impurities to create p-n junctions, which are the basic building blocks of photovoltaic cells. A p-n junction is a boundary between two types of semiconducting material, one of which has a surplus of electrons (n-type) and the other has a shortage of electrons (p-type). When sunlight hits a p-n junction, it creates an electric field that separates the electrons and holes (the absence of electrons), which generates an electrical current.

Cadmium telluride (CdTe) is a thin-film material that is used in some photovoltaic cells because it is less expensive than silicon and can be deposited on flexible substrates. CdTe cells have a higher efficiency than silicon cells in low-light conditions, but they have lower efficiency at high temperatures. CdTe is also toxic, so proper disposal of CdTe cells is important to prevent environmental contamination.

Copper indium gallium selenide (CIGS) is another thin-film material that is used in some photovoltaic cells. CIGS has a high efficiency and can be deposited on flexible substrates, making it suitable for building-integrated photovoltaics (BIPV). However, CIGS cells are more expensive than CdTe cells and have lower durability.

In addition to the semiconducting material, photovoltaic cells also contain other materials that improve their performance. For example, the front surface of a cell is coated with an anti-reflective material that reduces the amount of sunlight that is reflected back into the atmosphere. The back surface of a cell is also coated with a reflective material that reflects the sunlight back into the cell to increase the amount of light that is absorbed.

Photovoltaic cells are typically arranged in modules or panels, which are then connected in series or parallel to produce the desired voltage and current. The electrical power produced by the cells can be used directly, stored in batteries, or fed into the electrical grid.

The efficiency of a photovoltaic cell is the percentage of the sunlight that is converted into electrical energy. The efficiency of silicon cells ranges from 15% to 25%, depending on the quality and thickness of the material. Thin-film cells have lower efficiency, ranging from 10% to 20%, but they are less expensive and can be produced in large quantities.

In conclusion, photovoltaic cells are made of semiconducting materials, such as silicon, cadmium telluride, and copper indium gallium selenide, that convert sunlight into electricity. The efficiency of the cells depends on the quality and thickness of the material, as well as the design of the cell. The use of photovoltaic cells as a means of generating renewable energy is growing in the United Kingdom and around the world, as more people recognize the benefits of reducing reliance on fossil fuels and mitigating climate change.