Poly-silicon or simply poly is a material consisting of multiple small silicon crystals. Polycrystalline silicon can be as much as 99.9% pure. It is most often mixed with oxygen in sand form. In today’s industry, pure silicon is either obtained via the Siemens process or, sometimes, though the fluid bed reactor (FBR) technology.
Semiconductor grade poly-silicon is converted to “single crystal” silicon – meaning that the randomly associated atoms of silicon in “polycrystalline silicon” are converted to large “single” crystals of silicon. Single crystal silicon is previously used to manufacture electronic devices. The applications can be found in almost everywhere in our daily life from the cell phone you use to large aircraft.
Poly-silicon is also a key material for solar modules. The photovoltaic solar industry is growing rapidly and has replaced semi-conductor industry as the main consumer of poly-silicon. But the requirement for silicon purity is not that demanding compared with semi-conductor industry. It is most commonly referred to as ‘solar grade silicon’. Previously, poly-silicon production is mainly dominated by a few global manufacturers including REC, Hemlock and Wacker. In recent years, a handful of companies, most of them of Chinese origin, have joined the silicon club by launching poly-silicon manufacturing plants.