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What Chemicals Are Used to Make Solar Panels?

With the increased awareness and concern of environmental issues, such as global warming, research into renewable forms of energy is becoming increasingly important. According to the U.S. Energy Information Administration (EIA), solar energy technologies produce only a fraction of a percent of the energy consumed in United States each year. However, solar energy has been slowly gaining popularity. The two main forms of solar energy technologies are solar thermal energy (STE) and photovoltaic (PV) energy. PV energy, in particular, turns solar energy directly into electric energy, via some form of semiconductor material. As of 2010, most PV solar panels use one of only a handful of chemicals as semiconductor material.

  1. Silicon

    • One of the most common chemical elements, silicon (SI) was "used to make some the earliest photovoltaic (PV) devices," according to the EIA. However, as of 2010, silicon is still the most common semiconductor material used in solar panels. Single-crystal silicon, the most efficient and expensive form of silicon PV material, is formed from high-purity molten silicon and grown from crystal "seeds." Multicrystalline silicon, which is less efficient but less expensive, can be created in a number of ways. Amorphous silicon, which is commonly used in calculators, is non-crystalline, and therefore less stable than crystalline silicon, when used in PV devices. However, like multicrystalline silicon, amorphous silicon costs less to manufacture.

    Gallium Arsenide

    • Gallium arsenide (GaAs) is a chemical compound, made up of gallium and arsenic. This compound has been more recently developed for a number of high-tech uses, including solar energy. As a single-crystalline film in PV panels, gallium arsenide is highly efficient; super-thin cells, only a fraction as thick as silicon cells, can absorb the same amount of energy as those same silicon cells. In addition, gallium arsenide is much more durable than most semiconductor materials, and suffers little radiation degradation. The major setback in using this chemical in solar panels is the cost of gallium. This byproduct of the smelting process is, according to the EIA, "rarer than gold."

    Polycrystalline Thin-Films

    • Polycrystalline thin-film is also a much more absorbent PV material than silicon. The film is typically made out of either copper indium diselenide (CuInSe2) or cadmium telluride (CdTe). Small amounts of gallium are sometimes added to the copper indium diselenide films, to increase the band gap, while the band gap of cadmium telluride is almost perfect for absorbing solar energy. Other chemicals that are sometimes added to both kinds of panels include cadmium sulfide (CdS) and zinc (Zn). Polycrystalline thin-films are still mostly in the research phase. However, according to University of Delaware's Institute of Energy Conversion, polycrystalline thin-films "appear to be the most promising candidates for large-scale application of photovoltaic energy conversion."

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