1. Overview of
polysilicon production Silicon was discovered by Swiss chemist Berzelius in 1823, and it was not until the invention of transistors in 1947 that it was valued and given a new mission. In 1954, Bell Laboratory of the United States successfully developed the first silicon transistor and the first monocrystalline silicon cell (efficiency about 6%). Silicon's semiconductor properties and abundance in the earth's crust have established its position as the cornerstone of the semiconductor field. There is no free silicon in
nature, and it exists in the form of oxide. The raw material of polysilicon is industrial silicon (Silicon metal), which is prepared from silica ore, including quartz sandstone, quartzite, quartz sand, vein quartz and metasomatic siliceous hornfels. Semiconductor materials require high purity. Due to the low content of silicon in silica ore, the purification of silicon is to obtain ordinary purity silicon (industrial silicon) first, and then further purify it to prepare ultra-high purity elemental silicon. The extraction and preparation of high-purity elemental silicon has extremely high requirements for the process. Industrial silicon, also known as metallic silicon or crystalline silicon, is obtained by reduction reaction of silica (main component SiO2 ≥ 99.2%, usually in the form of quartz or pebble) by carbonaceous reductant (washed coal, petroleum coke, charcoal, etc.) In a submerged arc furnace. Its nominal silicon content is not less than 98.
There are two types of elemental silicon: crystalline and amorphous. Crystalline silicon includes monocrystalline silicon and polycrystalline silicon. Its structure is similar to diamond. It is a gray-black solid with metallic luster. Wherein the polycrystalline silicon is formed by arranging silicon atoms into a plurality of crystal nuclei in a lattice form, the crystal nuclei grow into crystal grains with different crystal plane orientations, and the crystal grains are combined to crystallize into the polycrystalline silicon. According to the application, polysilicon can be divided into solar grade polysilicon and semiconductor grade polysilicon. Polycrystalline silicon is the raw material for pulling monocrystalline silicon. Monocrystalline silicon has higher electron mobility and good thermal stability, so monocrystalline silicon cells have higher conversion efficiency than polycrystalline silicon cells.
Figure 1: From silica ore to polysilicon
Source: Digital New Energy DataBM. In the 20th century, the purification process of silicon has been extensively studied, especially the thermal reduction reaction of silica ore and charcoal, which has promoted the development of industrial silicon industry. In 1955, the German SIEMENS Company developed the polycrystalline silicon deposition technology of reducing trichlorosilane by hydrogen on the silicon core at high temperature (the first generation Siemens method). However, the by-products SiHCl3 , SiCl4 , HCl and H2 are produced. Since then, the technology has been improved many times, in which the first generation of SIEMENS method has recovered SiHCl3 and H2. The second generation Siemens process further reacts SiCl4 with silicon and hydrogen to produce SiHCl3 for recycling, and the third generation Siemens process (called "modified Siemens process") has realized the closed cycle production of SiHCl4. Compared with the second generation, HCl is further recovered to participate in the preparation of SiHCl3 . At present, the mainstream polysilicon production process in China is the improved Siemens process (which is called the hydrogen reduction process of trichlorosilane in the Code for Design of Polysilicon Factories GB 51034-2014). In addition to improving the production process of Siemens method, some enterprises at home and abroad have also adopted silane method and fluidized bed method. Silane method uses silane as raw material to prepare polycrystalline silicon by thermal decomposition; fluidized bed method mainly produces granular polycrystalline silicon. At the end of the
last century, the global output of polysilicon was 1. In the early days of China, the traditional Siemens method was the main method of production, which had high energy consumption, heavy pollution and high cost, and the operation was difficult to sustain. After 1986, the company independently researched and developed new polysilicon production technology. By the end of 1999, the 100 tons/year polysilicon improved Siemens method industrial experimental demonstration line of Emei Semiconductor Material Factory was built. Together with Luoyang Silicon Monocrystal Factory, the total output was only 55 tons, with a large demand gap and strong import dependence. In 2003, the first domestic polysilicon production line with an annual output of 1000 tons was started in Leshan, Sichuan Province. At that time, the domestic import volume was as high as 750 tons. In 2007, the 1000-ton project was put into operation, and the polysilicon formally entered the large-scale production. The domestic polysilicon output exceeded 1000 tons for the first time. The 10000-ton investment project appeared, and the capacity of the projects under construction and planned to be built exceeded 60000 tons per year. With the release of production capacity, the output of polysilicon in China reached 8.08 tons in 2011. In 2022, the output of polysilicon in China reached 830,000 tons, and is expected to exceed 1.4 million tons in 2023.
Figure 2: Data Source of China's Polysilicon Production
from 1990 to 2022: Digital New Energy DataBM.com
II. Evolution
of Polysilicon Prices 2. Because of the high production cost, domestic polysilicon enterprises could not compete with imported silicon materials after the opening of the market, and the number of enterprises was closed down one after another, from more than 20 at that time to two at the end of the 1990s. In 1995, the price of imported polysilicon was above 600,000 yuan/ton. With the outbreak of the Asian financial crisis, the demand for semiconductor chips declined, the international silicon material market had excess capacity, and the price of imported silicon materials continued to fall. By 2000, the price of domestic polysilicon had dropped to about 250,000 yuan/ton. During the period from
2001 to 2003, the global annual PV installed capacity was stabilized at 300 ~ 500MW/year, the semiconductor industry market recovered, and the price of polysilicon was relatively stable, with a fluctuation range of 200,000-300,000 yuan/ton. In 2004, Germany revised the Renewable Energy Law to increase the subsidy of feed-in tariff, and Spain, France, Italy and other European countries also introduced subsidy policies, which led to a substantial increase in the installed capacity of photovoltaic in Europe, which led to the demand for silicon materials, and the price of polysilicon also rose to 450000 yuan/ton in 2004. The year 2004 is known as the first year of PV in the world. In this year, the newly installed capacity of PV in the world exceeded 1GW for the first time. Since then, it has continuously reached a new high. In 2005, the demand gap of PV cells for polysilicon continued to expand, resulting in a sharp rise in the price of silicon materials from 2004 to 2008, with a maximum of more than 3 million yuan/ton. The growth of demand from the photovoltaic sector is an important factor, and the lack of capacity expansion is also one of the reasons for the soaring price of silicon materials.
Figure 3: Price Trend
of Polysilicon from 2001 to 2008 Data Source: Digital New Energy DataBM.com
2. During the period from 2009 to 2019, although the price of polysilicon rebounded in some years, it generally showed a downward trend. The average price in 2019 is only 7.
Figure 4: The price trend
of polysilicon in 2009-2019 Data source: Digital New Energy DataBM. Com
2009-2019. The global PV installed capacity increased from 22.8G W to 584. Under the background of demand growth, the price of silicon materials continued to decline. According to our analysis, the main reasons are market surplus, import shocks and technological progress in the later period, and the rebound of intermediate prices in some years is mainly affected by the increase of installed demand driven by photovoltaic subsidy policy.
From 2008 to 2013, China's polysilicon production capacity has been continuously released, the capacity utilization rate is below 50% in most years, and the contradiction of excess capacity is prominent. During this period, China's photovoltaic market is highly dependent on foreign countries, and more than 90% of photovoltaic modules were exported overseas in 2011. The impact of the financial crisis and the "double reverse" investigation and high "double reverse" tax imposed by European and American countries on China's photovoltaic products since 2011 have greatly hit China's export trade of photovoltaic products. In 2012, the total import and export volume of solar photovoltaic products in China was 28.95 billion US dollars, with a year-on-year decrease of 32%, of which the export volume was 23.3 billion US dollars, with a year-on-year decrease of 35%, the export volume decreased by 8.1%, and the export price decreased by 29. In 2013, the export continued to decline, especially the export volume of photovoltaic cells and modules to the European market decreased by 62%. During this period, polysilicon exported from South Korea and the United States to China was sold at very low prices, further accelerating the decline in domestic silicon prices.
From 2014 to 2018, the price of polysilicon generally fluctuated between 100,000 yuan/ton and 150,000 yuan/ton. The domestic photovoltaic subsidy policy drove the price of silicon materials to rise periodically, while the decline in the production cost of silicon materials restricted the price rebound.In 2013, the State Council issued . Due to the high production cost of domestic silicon materials, most polysilicon enterprises still suffered losses in 2013-2014. In 2015, under the pressure of low import prices, domestic polysilicon prices returned to decline, falling to a new low since the financial crisis at the end of the year. At the end of
: Insufficient supply and strong demand drive the price of silicon materials to soar
. In 2020, the national polysilicon production capacity reached 457,200 tons, slightly lower than that in 2019, while in the second half of 2020, the epidemic situation was under control and the economy recovered, and the new installed capacity of photovoltaic increased significantly. The price of polysilicon showed a trend of first low and then high throughout the year, rising from 60,000 yuan/ton at the bottom to 9 in September. In 2021, China took the lead in recovering from the epidemic, with strong growth in overseas PV orders and further growth in new domestic installed capacity. The supply of polysilicon was in short supply, and the price rose sharply, from about 80,000 yuan/ton at the beginning of the year to more than 260,000 yuan/ton. This year, the photovoltaic industry chain from industrial silicon to components has seen a sharp rise in the whole link, mainly driven by short-term demand. Due to the insufficient supply of polysilicon, the installation progress of downstream components will be affected. With the release of new production capacity of silicon materials in 2022, the production capacity doubled year-on-year, the output in the fourth quarter increased by more than 90% year-on-year, the supply-demand relationship slowed down, and the price of silicon materials dropped rapidly from a high level at the end of the year.
Figure 5: Price Trend of Polysilicon in 2020-2023 (yuan/ton)
Data Source: Digital New Energy DataBM.
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