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Silicon wafers are divided into semiconductor wafers and photovoltaic wafers according to their uses. Photovoltaic silicon wafers can be single crystal silicon or polycrystalline silicon, and semiconductor silicon wafers can only be single crystal silicon. The biggest difference between the two is that the content and purity of silicon are different. The conversion efficiency of monocrystalline silicon is generally about 18.5%~25%, and the conversion efficiency of polycrystalline silicon wafer is about 17.3%. Correspondingly, monocrystalline silicon solar cells have higher photoelectric conversion efficiency than polycrystalline silicon solar cells.
Over the years, the silicon wafer size has experienced a process from small to large. The increase in silicon wafer size and the continuous progress of photovoltaic technology have promoted the cost reduction and efficiency improvement of the entire photovoltaic industry chain.
For silicon wafer manufacturers, the larger size of silicon wafers can reduce the three major costs of silicon wafer companies: silicon material, crystal pulling, and slicing. The same amount of silicon material can reduce the number of crystal pulling and energy consumption when the diameter of the silicon rod becomes larger, thereby reducing the cost of crystal pulling. At the same time, large-sized silicon wafers can reduce the number of slices, the cost of slices and the cost per watt of silicon wafers.
For solar cell and solar panel manufacturers, the larger size of silicon wafers can speed up the production speed of silicon wafers to solar modules, which will also reduce production and operation costs such as manpower, water and electricity, and dilute the production process of solar cell modules. Non-silicon cost. As the size of a single silicon wafer increases, the number of cells in a single solar module decreases, the number of silicon wafers decreases accordingly, and the effective light-emitting area of the solar module increases, which will lead to an increase in conversion efficiency and power, and a decrease in the cost per watt. .
For power station customers, under the same power station scale, the larger the size of the solar modules, the less the number of solar modules required, thereby reducing the corresponding brackets, combiner boxes, cable costs, transportation and installation costs, etc. At the same time, large-sized silicon wafers will improve the power and quality of solar modules to a certain extent, and increase the power generation capacity of the power station while reducing the cost of the power station.
Under the driving force of diluting costs and improving the quality of solar modules, the silicon wafer size has grown from 100mm to 210mm in the past 40 years from 1981 to the present.
Between 1981 and 2012, silicon wafers had margins of 100mm and 125mm, and were dominated by 125mm silicon wafers. After that, the margin of silicon wafer was greatly increased from 125mm to 156mm (ie M0), an increase of 54.1%. 156mm silicon wafer has gradually become a popular choice for p-type monocrystalline and polycrystalline silicon wafers. Around 2014, 125mm P-type silicon wafers were basically eliminated and only used in some IBC and HIT battery modules.
At the end of 2013, several major manufacturers took the lead in unifying M1 (margin 156.75mm, diameter 205mm) and M2 (margin 156.75mm, diameter 210mm) silicon wafers with a standard of 156.75mm, which is a major change in the history of silicon wafer size development. . In 2017, the size standard was reviewed and approved by the SEMI standards committee. The revised version of the national standard for polysilicon wafers in 2018 also determined 156.75mm as the standard side length, and suggested that future size increases should be changed in multiples of 1mm.
2018 to present: M2—M6
Under the situation of increasing demand for high-power components, some manufacturers began to achieve this goal by increasing the area of the battery, resulting in the emergence of 157.0, 157.3, 157.5, 157.75, 158.0 and other silicon wafers in the market. The organization and management of the chain brings great inconvenience.
After the melee, two mainstream sizes appeared on the market: G1 square monocrystalline (158.75mm margin) and M6 (166mm margin) large silicon wafers.
The ultimate in wafer size: 210mm
In August 2019, Zhonghuan launched the G12 (210mm margin) large silicon wafer, which greatly increased the area of the M6 silicon wafer by 60.8%. According to the data, the cost of G12 cells is 25.56% lower than that of M2, and the cost of components is reduced by 16.8%.
The change in the size of silicon wafers over the past 40 years reflects the parity process of the entire industry. With the advent of the parity era, a new starting point for the photovoltaic industry has just begun.