Properties and Production of Polycrystalline Silicon
Polysilicon, also known as polysilicon, is a high purity form of silicon used to manufacture photovoltaic (PV) solar panels. It consists of many small silicon crystals or grains. While mono-crystalline silicon contains a single silicon crystal, polysilicon is made up of multiple small crystals aligned in random orientations. Polysilicon derives its properties based on the orientation and size of these individual silicon crystals.
Polycrystalline Silicon is produced through a high temperature process known as the Siemens process. In this process, trichlorosilane gas is purified and reacted with hydrogen at around 1100°C inside a reactor heated by an electric arc. This causes the silicon atoms in trichlorosilane to separate and deposit onto rods made out of silicon, growing polysilicon ingots. The ingots are then sliced into thin wafers and undergo additional purification steps to achieve 99.9999% purity needed for solar cell manufacturing. On average, it takes around 50 kilograms of polysilicon to produce 1 megawatt of solar panel output.
Role of Polycrystalline Silicon in Solar PV Industry
Polysilicon plays a vital role in the solar energy industry as it is a key raw material for manufacturing most types of solar PV panels. Around 90% of the global solar PV module production uses polysilicon as the base material. Within solar cells, the polysilicon layer forms the positive side that absorbs sunlight and generates electricity. Due to its abundance, high purity and specialized electronic properties, polysilicon remains the most suitable material for converting solar energy into electric current on a large commercial scale.
Any fluctuation in the supply or prices of polysilicon can have far-reaching impacts across the entire solar value chain. During 2007-2008, a polysilicon shortage raised solar panel prices and acted as a drag on the growth of solar installations worldwide. Similarly, an oversupply of polysilicon during 2015-2017 put intense downward pressure on global solar module prices. As solar PV capacities continue rising to meet climate change goals, a steady and affordable supply of polysilicon will remain crucial.
Leading Producers and Global Market Dynamics
China dominates the global polysilicon production with a share of over 70% of the market. The top Chinese producers include GCL-Poly, Daqo New Energy, Xinte Energy and East Hope Group. Outside China, major polysilicon manufacturing companies are Wacker Chemie, Hemlock Semiconductor, OCI and REC Silicon.
Between 2010 and 2020, annual global polysilicon production capacity grew rapidly from 45,000 metric tonnes to over 550,000 metric tonnes currently. This was led by massive capacity additions in China to meet the country's internal solar panel demand as well as exports. However, overcapacity led to a downcycle during 2017-2019 when prices fell below production costs. This forced many high-cost producers to reduce or halt output.
After bottoming at $7.50/kg in 2018, polysilicon prices recovered to the $9-10/kg range in 2020 mainly due to capacity cuts. For 2021-22, prices are projected to stabilize further between $8.50-9.50/kg as demand picks up while new capacity additions remain limited amid the pandemic. Looking ahead, polysilicon makers are optimistic about long-term demand driven by global solar capacity targets and incentives for clean energy adoption.
Use of Polysilicon in Other Industries
In addition to PV solar, polysilicon finds applications in the microelectronics industry for manufacturing semiconductor wafers, integrated circuits and other silicon devices. It is used as a specialty material in a variety of construction, automotive and aerospace applications where strength, durability and heat resistance are crucial factors.
Polysilicon is also being researched for potential next-generation uses in batteries, hydrogen storage and thermoelectric devices. There is ongoing R&D into developing high surface area porous polysilicon for advanced lithium-ion batteries that could significantly boost electric vehicle driving ranges. New production methods to synthesize tailored nano-sized polysilicon particles could unlock many more applications in the future across different sectors.
Going forward, polysilicon demand is projected to grow steadily at 4-5% annually through 2030 to support the expansion of clean energy generation worldwide. International climate change goals will further accelerate the adoption of solar energy which should maintain strong offtake of polysilicon raw material. Innovation in solar cell technology could also drive higher polysilicon usage per watt of installed PV capacity over time.
as a key driver of solar energy proliferation, the polysilicon industry is well-positioned for continued growth aligned with global decarburization efforts. Stable long-term policies, supply chain resilience and technological advances will be important factors in sustaining a healthy polysilicon manufacturing sector for powering the solar revolution.
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