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What are the links you have overlooked for the standardization of silicon used in solar panels?

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Issuing time:2020-01-13 16:46

One of the first important raw materials we need to prepare for the production of solar panels is solar cells. Why do you say that? Some people who know the solar panel industry know that the conversion efficiency of solar panels with different specifications is different, and the specifics are different. How about it?

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A small increase in the size of the silicon wafer can bring a small increase in the output of the battery and module production line, thereby reducing the production cost per watt, and improving the module power and conversion efficiency without changing the module size. In addition, the most simple way to enter the 4.0 or 5.0 era is to increase the size of the battery and components. Many companies have fine-tuned the size of silicon battery cells to achieve a competitive advantage in their products. As a result, there have been multiple choices for the size of silicon wafers, which has caused troubles in the upstream and downstream coordination of the industry chain. Increased product inventory. Therefore, there is an urgent need to develop a silicon wafer size standard. Through the discussion and voting of the industry's major silicon wafer and battery module companies in the past two years, three silicon wafer sizes have been selected as the industry recommended standard sizes, which are 156.75mm, 158.75mm, and 166.00mm.


1. Origin of silicon wafer size, necessity of development and specification


Since the photovoltaic wafer material was originally derived from semiconductor single crystals, the wafer size of the photovoltaic industry has always used semiconductor wafer sizes of 6 inches and 8 inches (diameter), which corresponds to the so-called 5 inch wafer (125mm). And 6 inches (156mm). Due to the progress of battery production equipment and the demand for increased output, 5-inch chips have gradually withdrawn from the photovoltaic industry chain. After 2012, except for 1-2 special battery manufacturers, 125mm silicon wafers were basically eliminated from the market.


The industry's first attempt to slightly increase the size of silicon wafers was in 2015. Single crystal silicon wafer manufacturers increased the side length of 156.00mm to 156.75mm, and reduced the chamfer of single crystal silicon wafers. sheet. This size standard amendment was reviewed and approved by the SEMI Standards Committee in 2017. In this way, the side length of a single polycrystalline silicon wafer has actually begun to unify to the size of 156.75mm. The polysilicon wafer national standard also identified 156.75mm as the standard side length in the 2018 revision, and suggested that future size increases be changed by multiples of 1mm.


However, this unified size did not last for long. Some companies in the industry began to fine-tune the size of their batteries again, in pursuit of the highest conversion efficiency and power output of the components under the existing size, so as to meet the requirements of China's "leader project" The film size is 157.0mm, 157.3mm, 157.5mm, 157.75mm, 158.0mm and so on based on the 156.75mm standard. Driven by the goal of over 400 watts of module power and the minimum investment in transformation, the existing battery and module production lines were used to reduce production costs to the greatest extent. The silicon wafer size has also changed by 158.75mm, 161.75mm, 166mm and so on.


The increase in the size of silicon wafers and batteries is conducive to the decline in the processing cost per watt of the industrial chain from silicon wafers to batteries, especially to modules, and is an important direction for the technological progress of the industry. The increase in the power of a single-chip module, or even the increase in the size of the module, is an effective way to reduce the cost of electricity as long as the market installation can accept it. Therefore, the increase in the size of silicon wafers is the development trend of photovoltaic manufacturing. Standardizing the size of future silicon wafers, forming a standard commonly adopted by the entire industry, has become a common demand of photovoltaic manufacturing enterprises.


At present, the diversification of silicon wafer sizes in the industry has caused great trouble for the industry chain from silicon wafers to batteries to modules. Silicon wafers produced for a particular size of a battery cannot be circulated to other customers, which easily causes inventory and causes Waste, again, some sizes of batteries are not easy to find other buyers, causing backlogs and so on. Due to the uncertainty of the size of future silicon wafers, equipment providers cannot fully develop new-generation batteries, module equipment, and so on. Therefore, the size of silicon wafers urgently needs to be unified and standardized.


Since 2017, under the organizational structure of IEC TC82 / WG8, the major silicon wafers, battery components, equipment manufacturing and testing units of the industry have been organized to discuss and formulate the standard geometric size standards for crystalline silicon wafers used in photovoltaic cell production. We recommend several wafer sizes based on the more widely used in current large-scale production, and give expected guidance for future wafer sizes. The crystalline silicon wafers here include single crystal silicon wafers produced by CZ direct-pulling, polycrystalline silicon wafers grown by ingot casting, and single crystal silicon wafers.


2. Principles of silicon wafer size


First of all, we have to realize that there is no question of which silicon wafer size is right, which is wrong, and that there is not even one technology that is better than the other. The size that is recommended for standard adoption is what most companies are willing to accept. To avoid too much controversy, we confirm the following basic principles:


1) The size of the silicon wafer should be as small as possible. Among the silicon wafer sizes that can be accepted through the modification of existing battery and module production equipment, try to confirm a size that everyone accepts as a recommended and promoted standard size.


2) It is necessary to prevent different sizes with small changes above the standard size, such as an increase of <1.0 mm. Many existing small changes that occur above 156.75mm are based on maximizing the use of the component size of the enterprise itself and minimizing the transformation of equipment, which should be avoided as much as possible.


3) Make specification recommendations for the size of silicon wafers that can be adopted by new or through the largest transformation of battery module production and testing equipment, and make the increment between the recommended sizes as large as possible, and be accepted by the module application side.


4) For the larger silicon wafer size in the future, confirm a minimum increase to guide the determination of the new size in the future technology development.


5) For quasi-square silicon wafers, the diameter of the ingot is not enforced, but recommended values are given.


3. Several standard sizes confirmed basically


After discussion and revision in the past two years, the draft standard of crystalline silicon wafer size was basically determined at the IEC TC82 / WG8 conference in Shanghai in early June this year. Several controversial issues, such as whether to keep .75 in future sizes, whether to skip 161.75mm and so on, the result of the debate is basically formed by voting:


1) The standard size of silicon wafers is recommended at this stage: 156.75mm, 158.75mm and 166.00mm. Other sizes are non-standard sizes, which can be adopted by both the supplier and the buyer through consultation.


2) In the range of the size smaller than 166mm, the increase in the size of the silicon wafer relative to 156.75mm is a multiple of 1mm. For example, 157.75mm, 158.75mm, 163.75mm, etc. Avoid 157.0mm, 161.5mm, etc.


3) In the size range larger than 166mm, the increase in the size of the silicon wafer relative to the 166.00mm is a multiple of 1mm. For example, 168.00mm, 180.00mm, 210.00mm, etc. Avoid 168.75mm, 171.5mm, etc.


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