From Quartz to a Solar Cell - Wacker Chemie AG


From Quartz to a Solar Cell

WACKER is famous for the particularly high purity of its polycrystalline silicon. in 2016, the Group opened a new, ultra-modern polysilicon fab in Tennessee. Click here to see how the hyperpure material is made.

Polysilicon supply chain

  • Polysilicon supply chain

    The starter material for polysilicon is quartz (SiO2).

  • Polysilicon supply chain

    When silicon dioxide (SiO2) is heated together with carbon, oxygen atoms are extracted from the SiO2 . What remains is metallurgical grade silicon (mg-Si). It contains between 1 and 2 percent impurities.

  • Polysilicon supply chain

    The metallurgical grade silicon (mg-Si) is made to react with hydrogen chloride (HCl) inside a fluid bed reactor to yield liquid trichlorosilane (HSiCl3). Having the silicon in this form makes industrial-scale cleanup easier.

  • Polysilicon supply chain

    Distillation yields trichlorosilane of extremely high purity.

  • Polysilicon supply chain

    Inside the reactor, the highly pure, distilled trichlorosilane is heated to about 1,000 °C and passed over thin, heated silicon ingots.

  • Polysilicon supply chain

    The trichlorosilane decomposes and the silicon atoms are deposited on the ingots, where they form a highly pure polycrystalline layer (Siemens process).

  • Polysilicon supply chain

    The hyperpure silicon is broken into chunks.

  • Polysilicon supply chain

    Polycrystalline solar cells account for about two-thirds of the world market. For this application, the polysilicon chunks are cast in the form of oblong blocks.

  • Polysilicon supply chain

    The polysilicon blocks are sawn into ultrathin wafers about 180 microns thick.

  • Polysilicon supply chain

    One of the many manufacturing steps involves connecting the wafers to each other electrically.

  • Polysilicon supply chain

    If the finished photovoltaic module is now exposed to sunlight, it will generate electric current.

Facts about the polysilicon plant in Charleston, Tennessee:

  • US$2.5 billion capital expenditure
  • Over 20,000 metric tons a year production capacity.
  • Roughly 650 new jobs created
  • 2,226,000 m2 undeveloped land/factory space