Composition for preparing N-type silicon single crystal rod and method for preparing N-type silicon single crystal rod

Abstract

The invention belongs to the technical field of silicon single crystal rod preparation. The invention provides a composition for preparing an N-type silicon single crystal rod and a method for preparing the N-type silicon single crystal rod. The composition comprises a circulating material and a first silicon material, and the first silicon material comprises at least two of an N-type compact material, a P-type compact material and a coral material. According to the composition for preparing the N-type silicon single crystal rod, the qualified N-type silicon single crystal rod can be prepared by adopting the circulating material and the first silicon material, and meanwhile, the production cost of the silicon single crystal rod (such as the N-type silicon single crystal rod) can be reduced.

Description

Technical Field

[0001] This application relates to the technical field of single crystal silicon rod preparation, and particularly relates to a composition for preparing an N-type single crystal silicon rod and a method for preparing an N-type single crystal silicon rod. Background Art

[0002] With the continuous growth of the global demand for clean energy, the photovoltaic industry, as an important part of renewable energy, is developing at an increasingly rapid pace. Against the backdrop of intensified competition in the photovoltaic industry, silicon materials are the core raw materials for photovoltaic cells.

[0003] Currently, the cost issue of core raw materials has become a key factor restricting the further development of the photovoltaic industry. Specifically, for Czochralski single crystals, it is particularly important to reduce production costs and improve crystal quality.

[0004] Therefore, developing a formulation solution to effectively reduce the cost of silicon materials is of great significance for enhancing the competitiveness of photovoltaic enterprises and promoting the sustainable development of the photovoltaic industry.

[0005] It should be noted that the above content is not necessarily prior art and is not used to limit the patent protection scope of this application. Summary of the Invention

[0006] Embodiments of this application provide a composition for preparing an N-type single crystal silicon rod and a method for preparing an N-type single crystal silicon rod to solve or alleviate technical problems such as the relatively high cost of producing single crystal silicon rods mentioned above.

[0007] In a first aspect of embodiments of this application, a composition is provided. The composition includes recycled material and first silicon material, wherein the first silicon material includes at least two of N-type dense material, P-type dense material, and coral material.

[0008] For the composition for preparing an N-type single crystal silicon rod in embodiments of this application, using recycled material and first silicon material can produce qualified N-type single crystal silicon rods while reducing the production cost of single crystal silicon rods (such as N-type single crystal silicon rods). This is because the recycled material can reduce the wire breakage rate, ensuring the single output during crystal pulling, and at the same time, the processing cost of self-recycled material is much lower than the cost of purchasing virgin polysilicon; the coral material can greatly reduce the silicon material usage cost, and the N-type dense material and P-type dense material can improve the quality of single crystal silicon rods while ensuring the single output, thereby reducing the cost. Thus, when the composition contains recycled material and first silicon material, qualified N-type single crystal rods can be prepared using the composition while reducing the production cost.

[0009] According to an embodiment of this application, based on the total mass of the composition, the mass of the recycled material is 45wt% - 60wt%, and the mass of the first silicon material is 40wt% - 55wt%.

[0010] According to an embodiment of the present application, the first silicon material is the coral material and the N-type dense material. In the composition, the mass ratio of the N-type dense material, the coral material, and the recycled material is (15-25):(20-30):(45-60).

[0011] According to an embodiment of the present application, the first silicon material is the P-type dense material and the N-type dense material. In the composition, the mass ratio of the N-type dense material, the P-type dense material, and the recycled material is (10-20):(20-40):(45-60).

[0012] According to an embodiment of the present application, the first silicon material is the P-type dense material and the coral material. The mass ratio of the P-type dense material, the coral material, and the recycled material is (10-30):(15-35):(45-60).

[0013] According to an embodiment of the present application, the first silicon material is the P-type dense material, the coral material, and the N-type dense material. The mass ratio of the N-type dense material, the P-type dense material, the coral material, and the recycled material is (1-10):(10-20):(15-25):(45-60).

[0014] In a second aspect of the embodiments of the present application, a method for preparing an N-type single crystal silicon rod using the composition described in the first aspect is provided, including the following steps: providing a furnace body, wherein a crucible is arranged in the furnace body; adding the composition and a master alloy into the crucible and melting the materials, and then pulling a single crystal to obtain a single crystal silicon rod. By using the method of the present application, an N-type single crystal silicon rod with better quality can be obtained, and the production cost can be reduced.

[0015] According to an embodiment of the present application, when the composition includes the coral material, the operation of adding the composition and the master alloy into the crucible and melting the materials includes: adding an initial charge and the master alloy into the crucible and melting the materials; when the initial charge starts to melt, adding the composition and the master alloy into the crucible; wherein, the initial charge includes the recycled material and a second silicon material, and the second silicon material includes the N-type dense material and / or the P-type dense material.

[0016] According to an embodiment of the present application, the operation of adding the composition into the crucible includes: placing the coral material at the bottom of the barrel.

[0017] According to an embodiment of the present application, the melting temperature is 1300°C - 1700°C.

[0018] According to an embodiment of the present application, the melting pressure is 530 Pa - 800 Pa.

[0019] According to an embodiment of the present application, the method further includes: looping through a preset step: the preset step is to add a replenishment charge and the master alloy into the crucible, and after the replenishment charge is completely melted, pulling a single crystal; the replenishment charge is the composition.

[0020] According to an embodiment of the present application, the number of times of looping through the preset step is 6 to 10 times.

[0021] According to an embodiment of the present application, the method further includes: adding a finishing charge into the crucible and melting the charge; after the finishing charge is completely melted, pulling a single crystal, and the finishing charge includes the second silicon material and the recycled material. Description of the Drawings

[0022] In the drawings, unless otherwise specified, the same reference numerals throughout the several views denote the same or similar components or elements. These drawings are not necessarily drawn to scale. It should be understood that these drawings only depict some embodiments disclosed in accordance with the present application and should not be regarded as limiting the scope of the present application.

[0023] Figure 1 It is an external morphology diagram of the N-type dense material according to an embodiment of the present application; Figure 2 It is an external morphology diagram of the P-type dense material according to an embodiment of the present application; Figure 3 It is an external morphology diagram of the coral material according to an embodiment of the present application; Figure 4 It is a charging schematic diagram of adding the composition according to an embodiment of the present application.

[0024] Reference Numerals: 1: Second silicon material; 2: Recycled material; 3: Coral material. Detailed Description of the Embodiments

[0025] The embodiments of the present application will be described in detail below. The examples of the embodiments are shown in the drawings. In the drawings, for clarity, the dimensions of layers, regions, elements, and their relative dimensions may be exaggerated. Among them, the same or similar reference numerals throughout denote the same or similar elements or elements having the same or similar functions. The embodiments described below by referring to the drawings are exemplary and are only used to explain the present application and should not be construed as limiting the present application. It should be noted that, without conflict, the embodiments in the present application and the features in the embodiments may be combined with each other.

[0026] It should be understood that when an element or layer is referred to as "on", "adjacent to", "connected to", or "coupled to" another element or layer, it can be directly on, adjacent to, connected, or coupled to the other element or layer, or there may be intervening elements or layers. In contrast, when an element is referred to as "directly on", "directly adjacent to", "directly connected to", or "directly coupled to" another element or layer, there are no intervening elements or layers. It should be understood that although the terms first, second, third, etc. may be used to describe various elements, components, regions, layers, and / or parts, these elements, components, regions, layers, and / or parts should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer, or part from another element, component, region, layer, or part. Thus, without departing from the teachings of the present application, the first element, component, region, layer, or part discussed below may be referred to as the second element, component, region, layer, or part. And when discussing the second element, component, region, layer, or part, it does not indicate that there must be a first element, component, region, layer, or part in the present application.

[0027] In the present application, unless otherwise clearly specified and defined, the terms "mounted", "connected", "coupled", "fixed", etc. shall be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or integrated; it may be a mechanical connection or an electrical connection; it may be directly connected or indirectly connected through an intermediate medium, and it may be the communication inside two elements or the interaction relationship between two elements, unless otherwise clearly defined. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to specific circumstances.

[0028] It should be noted that the terms "first", "second", etc. in the description, claims, and above-mentioned drawings of the present application are used to distinguish similar objects and do not necessarily need to be used to describe a specific order or sequence. It should be understood that these terms can be interchanged under appropriate circumstances so that the embodiments of the present application described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or device that includes a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products, or devices.

[0029] In this application, when it comes to numerical intervals (i.e., numerical ranges), unless otherwise specified, the distribution of the selectable numerical values within the numerical interval is considered continuous, and includes the two numerical endpoints of the numerical interval (i.e., the minimum value and the maximum value), as well as each numerical value between these two numerical endpoints. Unless otherwise specified, when the numerical interval only refers to the integers within the numerical interval, it includes the two endpoint integers of the numerical range, as well as each integer between the two endpoints, which is equivalent to directly listing each integer. When multiple numerical ranges are provided to describe features or characteristics, these numerical ranges can be combined. In other words, unless otherwise specified, the numerical ranges disclosed in this application should be understood to include any and all sub-ranges subsumed therein. The "numerical value" in the numerical interval can be any quantitative value, such as a number, a percentage, a ratio, etc. The "numerical interval" allows for a broad inclusion of quantitative intervals such as percentage intervals, ratio intervals, ratio value intervals, etc.

[0030] Currently, silicon material production enterprises mainly try to reduce costs through the following several ways: (1) Establish a recycling mechanism: By establishing a recycling mechanism for polysilicon materials, ensure that waste or damaged polysilicon can be recycled and reused, reducing the dependence on new raw materials. (2) Optimize the production process: By optimizing the production process flow, reduce the waste and loss of polysilicon materials, and improve the utilization rate of raw materials. (3) Internal recycling: During the production process, try to achieve internal recycling of polysilicon materials as much as possible to reduce the demand for fresh raw materials. (4) Technological innovation and process improvement: Through continuous technological innovation and process improvement, improve production efficiency and reduce production costs. (5) Reasonable procurement strategy: Develop a reasonable procurement strategy, negotiate with suppliers, and strive for more favorable procurement conditions to reduce raw material costs. Although the above measures have reduced the silicon material cost to a certain extent, in the current market environment, it is still difficult to meet the requirements of the photovoltaic industry for lower costs and higher efficiency.

[0031] Accordingly, in the first aspect of the embodiments of this application, a composition for preparing a single crystal silicon rod is proposed. The composition includes recycled material and a first silicon material, wherein the first silicon material includes at least two of N-type dense material, P-type dense material, and coral material.

[0032] The composition for preparing N-type single-crystalline silicon rods according to the embodiments of the present application can produce N-type single-crystalline silicon rods with qualified quality by using recycled materials and first silicon materials, and at the same time, can reduce the production cost of single-crystalline silicon rods (such as N-type single-crystalline silicon rods). This is because the recycled materials can reduce the wire breakage rate, ensure the single output during crystal pulling, and at the same time, the processing cost of self-recycled materials is much lower than the cost of purchasing virgin polysilicon; the coral materials can greatly reduce the silicon material usage cost, and the N-type dense materials and P-type dense materials can improve the quality of single-crystalline silicon rods while ensuring the single output, thereby reducing the cost. Therefore, when the composition contains recycled materials and first silicon materials, qualified N-type single-crystalline rods can be prepared by using the composition, and at the same time, the production cost can be reduced.

[0033] In some embodiments, based on the total mass of the composition, the mass of the recycled materials is 45wt% - 60wt%, such as 45wt%, 50wt%, 60wt%, 65wt%, etc., and the mass of the first silicon materials is 40wt% - 55wt%, such as 40wt%, 45wt%, 50wt%, 55wt%, etc. In this way, the production cost can be reduced while obtaining qualified N-type single-crystalline silicon rods.

[0034] In some embodiments, the first silicon materials are coral materials and N-type dense materials. In the composition, the mass ratio of the N-type dense materials, coral materials, and recycled materials is (15 - 25) : (20 - 30) : (45 - 60). Thus, the production cost can be reduced while obtaining qualified N-type single-crystalline silicon rods.

[0035] In some embodiments, the first silicon materials are P-type dense materials and N-type dense materials. In the composition, the mass ratio of the N-type dense materials, P-type dense materials, and recycled materials is (10 - 20) : (20 - 40) : (45 - 60). Thus, the production cost can be reduced while obtaining qualified N-type single-crystalline silicon rods.

[0036] In some embodiments, the first silicon materials are P-type dense materials and coral materials. The mass ratio of the P-type dense materials, coral materials, and recycled materials is (10 - 30) : (10 - 30) : (45 - 60). Thus, the production cost can be reduced while obtaining qualified N-type single-crystalline silicon rods.

[0037] In some embodiments, the first silicon materials are P-type dense materials, coral materials, and N-type dense materials. The mass ratio of the N-type dense materials, P-type dense materials, coral materials, and recycled materials is (0 - 10) : (10 - 20) : (15 - 25) : (45 - 60).

[0038] The term N-type dense material means that the virgin polysilicon is doped mainly with donor impurities (Group V elements, such as phosphorus, arsenic, antimony, etc.), the surface particle depression is less than 5mm, the cross-sectional structure is dense, the appearance has no abnormal color, and there is no oxidation interlayer. The macroscopic morphology of the N-type dense material can be seen in Figure 1。

[0039] The term P-type dense material refers to: in the as-grown polysilicon, the doping is mainly acceptor impurities (Group III elements such as boron, aluminum, gallium, etc.), the surface particle depression is less than 5 mm, the cross-sectional structure is dense, and there is no abnormal color on the appearance and no oxidation interlayer. The macroscopic morphology of the P-type dense material can be seen in Figure 2 。

[0040] The term coral material: the cross-sectional structure of the as-grown polysilicon is loose, the depression depth is ≥20 mm, there is no abnormal color on the appearance, and there is no oxidation interlayer. The macroscopic morphology of the coral material can be seen in Figure 3 。

[0041] The term recycled material: that is, the silicon material generated during the product manufacturing process that can be reused by being put into the furnace again, which contains impurities such as carbon, boron, phosphorus, iron, aluminum, copper, sodium, and zinc.

[0042] In some embodiments, the composition further includes a master alloy. The master alloy is a phosphorus-doped master alloy. When doping the phosphorus-doped master alloy, the N-type as-grown polysilicon and the P-type as-grown polysilicon are not distinguished, and the actual addition amount of the phosphorus-doped master alloy is based on the resistance grade of the recycled material. Among them, when calculating the amount of the phosphorus-doped master alloy, the polysilicon resistance is uniformly calculated as 10,000 ohms. Then, according to the doping software, the doping weight of the phosphorus in the master alloy is calculated.

[0043] In the second aspect of the embodiments of the present application, a method for preparing an N-type single crystal silicon rod using the composition of the first aspect is provided. The method includes the following steps: (1) providing a furnace body with a crucible disposed therein; (2) adding the composition and the master alloy into the crucible, melting the materials, and then pulling a single crystal to obtain the N-type single crystal silicon rod. By using the method of the present application, an N-type single crystal silicon rod with better quality can be obtained, and the production cost can be reduced.

[0044] According to the embodiments of the present application, in step (1), a furnace body is provided with a crucible disposed therein.

[0045] According to the embodiments of the present application, in step (2), after adding the composition and the master alloy into the crucible and melting the materials, a single crystal is pulled to obtain a single crystal silicon rod. In this step, the composition can be added into the crucible, and after the composition is completely melted, a single crystal silicon rod is pulled.

[0046] In some embodiments, melting the materials is to melt the raw material composition and the master alloy for preparing the N-type single crystal rod to facilitate pulling the single crystal silicon rod.

[0047] Optionally, the temperature for melting the materials is 1300~1700 °C, such as 1300 °C, 1400 °C, 1500 °C, 1600 °C, 1700 °C, etc.

[0048] Optionally, the pressure is 530 - 800 Pa, with exceptions such as 530 Pa, 600 Pa, 670 Pa, 730 Pa, 800 Pa, etc.

[0049] In some embodiments, step (3) is a loop of a preset step: the preset step is to add a re - feed and a master alloy to the crucible, and after the re - feed and the master alloy are completely melted, single - crystal pulling is performed. The re - feed is a composition. Thus, continuous single - crystal pulling can be achieved using the same crucible, thereby improving the production efficiency.

[0050] In some embodiments, the number of times of looping the preset step is adapted to the life of the crucible.

[0051] Optionally, the number of times of looping the preset step is 6 - 10 times, such as 6 times, 7 times, 8 times, 9 times, 10 times, etc.

[0052] In some embodiments, the process of single - crystal pulling further includes processes such as seeding, shoulder - releasing, shoulder - turning, equal - diameter, ending, and segment - taking steps until a complete ingot is pulled.

[0053] In some embodiments, the timing of adding the re - feed and the master alloy to the same crucible after pulling one N - type single - crystal ingot is when the weight of the silicon material in the crucible does not meet the full - crucible amount (for example, the full - crucible amount of a 36 - inch crucible is 940 kg), and secondary feeding is required.

[0054] In some embodiments, the method further includes step (4): adding a finishing material to the crucible and melting it; after the finishing material is completely melted, single - crystal pulling is performed. The finishing material includes a second silicon material and a recycled material. The quality of the products produced in the finishing section is relatively poor due to the enrichment of various impurities in the remaining materials in the crucible. When adding the finishing material in the finishing section, coral material is not used to improve the quality of the entire N - type single - crystal silicon ingot in the finishing section.

[0055] In the following embodiments, the absence of coral material in the composition is described: In some embodiments, obtaining the first N - type single - crystal silicon ingot includes: adding a composition, a master alloy to the crucible and melting them; when the composition and the master alloy start to melt, adding the composition and the master alloy to the crucible for the second time; after the composition and the master alloy added twice are completely melted, single - crystal pulling is performed, where the composition is a recycled material, an N - type dense material, and a P - type dense material.

[0056] Further, the operation of adding the composition and the master alloy to the crucible includes: placing the third silicon material at the bottom of the crucible and placing the recycled material on the third silicon material. The third silicon material is an N - type dense material and a P - type dense material, and the master alloy is placed in a box and directly poured into the crucible.

[0057] Further, the N-type dense material can be placed at the bottom of the barrel, and then the P-type dense material and the recycled material are stacked on top of the N-type dense material in sequence; alternatively, the P-type dense material can be placed at the bottom of the barrel, and then the N-type dense material and the recycled material are stacked on top of the P-type dense material in sequence; or the N-type dense material and the P-type dense material can be mixed and placed at the bottom of the barrel, and then the recycled material is placed on top of the mixture. Such an assembly of materials is beneficial to reducing silicon splashing during feeding and reducing wire breakage of the silicon rod during the single crystal pulling process, thereby improving the single output and the quality of the single crystal rod.

[0058] In some embodiments, there is a step of presetting the recycle: the preset step is to add the recycled feedstock and the master alloy into the crucible, and after the recycled feedstock and the master alloy are completely melted, single crystal pulling is carried out. The recycled feedstock is the recycled material, the N-type dense material and the P-type dense material. Among them, the charging method of the recycled feedstock is the same as the charging method during the production of the first N-type single crystal silicon rod.

[0059] In some embodiments, in the recycled feedstock, the mass ratio of the N-type dense material, the P-type dense material and the recycled material is (10~20)︰(20~40)︰(45~60).

[0060] In some embodiments, the method further includes step (4): adding the finishing material into the crucible and melting it; after the finishing material is completely melted, single crystal pulling is carried out. The finishing material includes the recycled material, the N-type dense material and the P-type dense material.

[0061] Optionally, the charging of the finishing material is the same as the charging method during the production of the first N-type single crystal silicon rod.

[0062] It can be understood that the master alloy is a phosphorus-doped master alloy. When doping with the phosphorus-doped master alloy, the N-type virgin polysilicon and the P-type virgin polysilicon are not distinguished, and the actual addition amount of the phosphorus-doped master alloy is based on the resistance grade of the recycled material. Among them, when calculating the amount of the phosphorus-doped master alloy, the resistance of the polysilicon is uniformly calculated as 10,000 ohms. Then, the doping weight of the phosphorus in the master alloy required is calculated according to the doping software.

[0063] In the following embodiments, the composition containing coral material is described: In some embodiments, the operation of adding the composition and the master alloy into the crucible and melting them includes: adding the initial charge and the master alloy into the crucible and melting them; when the initial charge and the master alloy start to melt, adding the composition and the master alloy into the crucible; after the initial charge, the composition and the master alloy are completely melted, single crystal pulling is carried out. Among them, the initial charge includes the recycled material and the second silicon material, and the second silicon material includes the N-type dense material and / or the P-type dense material. In this process, when the composition contains coral material, coral material is not added during the initial charging, and coral material is added only during the first charging (when adding the composition for the first time). This is beneficial to reducing the risk of silicon leakage and silicon penetration during the process of obtaining the first single crystal silicon rod.

[0064] In some embodiments, the operation of adding the initial charge and the master alloy into the crucible includes: placing the second silicon material at the bottom of the crucible and placing the recycled material on top of the second silicon material. Herein, the second silicon material is N-type dense material and / or P-type dense material. When adding the initial charge, the N-type dense material can be placed at the bottom of the barrel, and then the P-type dense material and the recycled material are stacked on top of the N-type dense material in sequence; or the P-type dense material can be placed at the bottom of the barrel, and then the N-type dense material and the recycled material are stacked on top of the P-type dense material in sequence; or the N-type dense material and the P-type dense material can be mixed and placed at the bottom of the barrel, and then the recycled material is placed on top of the mixture; the master alloy is placed in a box and directly poured into the crucible for addition. Such assembly of materials is conducive to reducing the breakage of the crucible when loading the initial charge into the crucible, thereby avoiding accidents such as silicon leakage and silicon infiltration.

[0065] In some embodiments, the initial charge is the recycled material and the N-type dense material. In the initial charge, the mass ratio of the recycled material to the N-type dense material is (40~50)︰(50~60).

[0066] Alternatively, the initial charge is the recycled material and the P-type dense material. In the initial charge, the mass ratio of the recycled material to the P-type dense material is (40~50)︰(50~60).

[0067] Alternatively, the initial charge is the recycled material, the N-type dense material, and the P-type dense material. In the initial charge, the mass ratio of the N-type dense material, the P-type dense material, and the recycled material is (10~20)︰(20~40)︰(45~60).

[0068] In some embodiments, referring to Figure 4 , the operation of adding the composition into the crucible includes: placing the coral material 3 at the bottom of the barrel and sequentially stacking the recycled material 2 and the second silicon material 1 on top of the coral material 3; the master alloy is placed in a box and directly poured into the barrel. In this way, the external dimensions of the coral material are smaller than those of other materials, and it can be used as a bottom layer when adding the composition, that is, the coral material is loaded at the bottom of the barrel, which can reduce the silicon splashing of the bulk material during feeding, thereby reducing the wire breakage during single crystal pulling.

[0069] Furthermore, it further includes transporting the barrel to the side of the furnace body and adding the composition into the crucible to pull a single crystal.

[0070] It can be understood that when adding the composition into the crucible, the composition can be divided into multiple barrels for feeding according to the actual feeding amount. For example, if 430 kg of the composition needs to be added into the crucible, this 430 kg of material is divided into 5 barrels for addition, which are 90 kg, 100 kg, 100 kg, 90 kg, and 50 kg respectively.

[0071] In some embodiments, adding the composite feedstock and the master alloy to the crucible includes: placing the coral material at the bottom of the barrel, and stacking the second silicon material and the recycled material on the coral material in sequence; transporting the barrel filled with the composite feedstock to the side of the furnace body, and adding the material to the crucible to draw a single crystal; the master alloy is placed in a box and directly poured into the barrel. In this process, the composite feedstock is consistent with the composition of the composition, so as to continuously draw a single crystal using the same crucible. Among them, the composite feedstock includes the recycled material, the coral material and the second silicon material, and the second silicon material includes N-type dense material and / or P-type dense material. When loading the composite feedstock, the N-type dense material can be placed above the coral material, and then the P-type dense material and the recycled material are stacked on the N-type dense material in sequence; or the P-type dense material can be placed above the coral material, and then the N-type dense material and the recycled material are stacked on the P-type dense material in sequence; or the N-type dense material and the P-type dense material can be mixed and placed above the coral material, and then the recycled material is placed above the mixture. Such a feeding arrangement is beneficial to reducing silicon splashing of the lump material during feeding, reducing wire breakage during crystal drawing, and thus improving the single output of the round rod.

[0072] It can be understood that when adding the composite feedstock to the crucible, the composite feedstock can be divided into multiple barrels for feeding according to the actual feeding amount.

[0073] In some embodiments, the first silicon material is the coral material and the N-type dense material. In the composition, the mass ratio of the N-type dense material, the coral material and the recycled material is (15-25):(20-30):(45-60).

[0074] In some embodiments, the first silicon material is the P-type dense material and the coral material. In the composition, the mass ratio of the P-type dense material, the coral material and the recycled material is (20-30):(10-30):(45-60).

[0075] In some embodiments, the first silicon material is the P-type dense material, the coral material and the N-type dense material. The mass ratio of the N-type dense material, the P-type dense material, the coral material and the recycled material is (0-10):(10-20):(15-25):(45-60).

[0076] In some embodiments, the finishing material is added to the crucible and melted; after the finishing material is completely melted, the single crystal is pulled. The finishing material includes the second silicon material and the recycled material. The quality of the products produced conventionally in the finishing section is poor due to the enrichment of various impurities in the remaining material in the crucible. The difference between the finishing material in the finishing section of the same crucible and the composite feedstock and the composition is that the coral material is not used when adding the finishing material in the finishing section, so as to improve the quality of the whole silicon rod in the finishing section.

[0077] Optionally, the usage ratio of the second silicon material and the recycled material during feeding in the finishing section is (40-50):(50-60).

[0078] Optionally, the feeding process of the finishing material includes: placing the second silicon material at the bottom of the barrel, stacking the recycled material on top of the second silicon material, transporting the loaded material to the side of the single crystal furnace after loading, feeding the material into the crucible, and performing single crystal pulling after the feeding is completed.

[0079] It can be understood that the master alloy is a phosphorus-doped master alloy. When doping the phosphorus-doped master alloy, N-type virgin polysilicon and P-type virgin polysilicon are not distinguished. The actual addition amount of the phosphorus-doped master alloy is based on the resistance grade of the recycled material. Among them, when calculating the amount of the phosphorus-doped master alloy, the polysilicon resistance is uniformly calculated as 10,000 ohms. Then, the doping weight of the master alloy phosphorus is calculated according to the doping software.

[0080] Hereinafter, exemplary embodiments according to the present application will be described in more detail with reference to the accompanying drawings. It should be noted that these exemplary embodiments can be implemented in many different forms and should not be construed as being limited only to the embodiments set forth herein.

[0081] Embodiment 1 S1. Furnace assembly: Open the silicon material package and start loading the initial charge. During the loading process, use P-type dense material as the bottom layer, with a proportion of 45%. The recycled material is loaded in the middle and upper parts of the crucible, with a proportion of 55% (this is the initial loading, loading 510 kg). After loading the material into the crucible, perform furnace assembly, install the hot field components according to the normal process, and close the furnace after the hot field installation is completed; also add 90.1 g of phosphorus-doped master alloy to the crucible during the initial loading. S2. Evacuation and leak detection: First, perform evacuation, and then perform leak detection (performed according to the evacuation and leak detection standard). S3. Pressure melting of the material: Turn on the heater and start automatic melting of the material. When melting the initial charge, perform the first addition of the combined material (first addition). S4. First addition: 430 kg of the first charge (composition) needs to be added during the first addition. Divide this 430 kg of material into 5 cylinders for addition, which are 90 kg, 100 kg, 100 kg, 90 kg, and 50 kg respectively. The mass ratio of P-type dense material, coral material, and recycled material in each cylinder is 20∶25∶55. When adding the material, the coral material is placed at the bottom of the barrel, the P-type dense material is in the middle, and the recycled material is on the top; after loading the first charge (composition), transport it to the side of the single crystal furnace and perform secondary feeding, with an interval of 60 min between each cylinder of feeding; during the first addition, 102.13 g of phosphorus-doped master alloy also needs to be added to the barrel. S5. Start crystal pulling: Pull out a complete N-type single crystal rod through the processes of seeding, shoulder release, shoulder turning, equal diameter, tailing, and section taking. This N-type single crystal rod is denoted as A11. After taking out the N-type single crystal rod, start secondary feeding. S6. Repeat steps S4 and S5 for 8 times. The N-type single crystal rods are sequentially denoted as A12, A13, A14, A15, A16, A17, and A18. S7. Final stage feeding: When feeding in the final stage, the usage ratio of P-type dense material and recycled material is 45:55. The P-type dense material is loaded at the bottom of the barrel, and the recycled material is loaded in the middle and at the top. After loading the material, it is transported to the side of the single crystal furnace for final stage feeding. After the feeding is completed, single crystal pulling is carried out normally. This N-type single crystal rod is denoted as A19.

[0082] Example 2 The preparation of the single crystal silicon rod is carried out in the same manner as in Example 1, except that in S4. First feeding: 430 kg of the first charge (composition) needs to be added in the first feeding. This 430 kg of material is divided into 5 barrels for addition, which are 90 kg, 100 kg, 100 kg, 90 kg, and 50 kg respectively. The mass ratio of P-type dense material, coral material, and recycled material in each barrel is 10:35:55.

[0083] 9 N-type single crystal rods are sequentially denoted as A21, A22, A23, A24, A25, A26, A27, A28, and A29.

[0084] Example 3 The preparation of the single crystal silicon rod is carried out in the same manner as in Example 1, except that in S4. First feeding: 430 kg of the first charge (composition) needs to be added in the first feeding. This 430 kg of material is divided into 5 barrels for addition, which are 90 kg, 100 kg, 100 kg, 90 kg, and 50 kg respectively. The mass ratio of P-type dense material, coral material, and recycled material in each barrel is 30:15:55.

[0085] 9 N-type single crystal rods are sequentially denoted as A31, A32, A33, A34, A35, A36, A37, A38, and A39.

[0086] Example 4 S1. Furnace assembly: Open the packaging of the silicon material and start loading the initial charge. During the loading process, use N-type dense material as the bottom layer, and the proportion of N-type dense material is 45%. The recycled material is loaded in the middle and upper parts of the crucible, and the proportion of the recycled material is 55% (this is the initial loading, loading 510 kg). After loading the material into the crucible, carry out furnace assembly, and install the thermal field components according to the normal process. After the thermal field installation is completed, close the furnace; during the initial loading, 90.1 g of phosphorus-doped master alloy is also added to the crucible; S2. Evacuation and leak detection: First, evacuate, and then detect leaks (performed according to the evacuation and leak detection standard); S3. Pressure melting of the material: Turn on the heater and start automatic melting of the material. When melting the initial charge, carry out the first addition of the combined material (first feeding); S4. First addition: 430 kg of first charge (composition) needs to be added. Divide this 430 kg of material into 5 cylinders for addition, which are 90 kg, 100 kg, 100 kg, 90 kg, and 50 kg respectively. For each cylinder, the mass ratio of N-type dense material, coral material, and recycled material is 20:25:55. When adding the material, the coral material is placed at the bottom of the cylinder, the N-type dense material is in the middle, and the recycled material is on the top. After loading the first charge (composition), transport it to the side of the single crystal furnace for secondary addition. The interval time between each cylinder addition is 60 min. During the first addition, 102.13 g of phosphorus-doped master alloy also needs to be added to the cylinder. S5. Start crystal pulling: Pull out a complete N-type single crystal rod through the processes of seeding, shoulder release, shoulder turning, equal diameter, tailing, and segment taking. This N-type single crystal rod is denoted as B1. After taking out the N-type single crystal rod, start secondary addition. S6. Repeat the steps of S4 and S5 for 8 times. The N-type single crystal rods are denoted as B2, B3, B4, B5, B6, B7, and B8 in sequence. S7. Final stage addition: During the final stage addition, the usage ratio of N-type dense material and recycled material is 45:55. The N-type dense material is placed at the bottom of the cylinder, and the recycled material is placed in the middle and at the top. After loading the material, transport it to the side of the single crystal furnace for final stage addition. After completing the addition, carry out single crystal pulling normally. This N-type single crystal rod is denoted as B9.

[0087] Example 5 S1. Assemble the furnace: Open the packaging of the silicon material and start loading the combined materials. When adding the materials, the mass ratio of N-type dense material, P-type dense material, and recycled material is 15:30:55. The N-type dense material is placed at the bottom of the cylinder, the P-type dense material is in the middle, and the recycled material is on the top. (The total initial charge is 510 kg). After loading the materials into the crucible, assemble the furnace and install the thermal field components according to the normal process. After the thermal field installation is completed, close the furnace. During the initial loading, 90.1 g of phosphorus-doped master alloy is also added to the crucible. S2. Evacuate and leak check: First evacuate, and then conduct a leak check (performed according to the evacuation and leak check standard). S3. Pressure melting of the material: Turn on the heater and start automatic melting of the material. While the combined materials are being melted, continue to add the combined materials (first addition). S4. First addition: 430 kg of the composition needs to be added. Divide this 430 kg of material into 5 cylinders for addition, which are 90 kg, 100 kg, 100 kg, 90 kg, and 50 kg respectively. For each cylinder, the mass ratio of N-type dense material, P-type dense material, and recycled material is 15:30:55. When adding the material, the P-type dense material is placed at the bottom of the cylinder, the N-type dense material is in the middle, and the recycled material is on the top. After loading the combined materials, transport it to the side of the single crystal furnace for secondary addition. The interval time between each cylinder addition is 60 min. During the first addition, 102.13 g of phosphorus-doped master alloy also needs to be added to the cylinder. S5. Start crystal pulling: Pull a complete N-type single crystal rod through the processes of seeding, shoulder expansion, shoulder rotation, equal diameter growth, tailing, and segment extraction. This N-type single crystal rod is denoted as C1. After removing the N-type single crystal rod, start the second feeding; S6. Repeat steps S4 and S5 for 8 times. The N-type single crystal rods are sequentially denoted as C2, C3, C4, C5, C6, C7, and C8; S7. Final segment feeding: During the final segment feeding, the mass ratio of N-type dense material, P-type dense material, and recycled material is 15:30:55. The N-type dense material is placed at the bottom of the barrel, the middle is N-type dense material, and the top is recycled material. After loading the materials, transport them to the side of the single crystal furnace for the final segment feeding. After completing the feeding, carry out single crystal pulling normally. This N-type single crystal rod is denoted as C9.

[0088] Comparative Example 1 S1. Assemble and furnace: Open the packaging of the silicon material and start loading. During the loading process, first use N-type dense material as the bottom layer, with a mass ratio of 45%. The recycled material is loaded in the middle and upper parts of the crucible, with a mass ratio of 55% (this is the initial loading, loading 510 kg). After loading the materials into the crucible, carry out furnace assembly. Install the thermal field components according to the normal process. After the thermal field installation is completed, close the furnace; During the initial loading, also add 90.1 g of phosphorus-doped master alloy to the crucible; S2. Evacuate and leak check: First evacuate, and then conduct a leak check (performed according to the evacuation and leak check standards); S3. Pressure melting of the material: Turn on the heater and start automatic melting of the material. When melting the initially loaded material, continue to add raw materials (first addition); S4. First addition: 430 kg of raw materials need to be added during the first addition. Divide these 430 kg of materials into 5 cylinders for addition, which are 90 kg, 100 kg, 100 kg, 90 kg, and 50 kg respectively. Each cylinder is lined with N-type dense material at the bottom, with a mass ratio of 45%. The recycled material is loaded in the middle and upper parts of the crucible, with a mass ratio of 55%; After loading the raw materials, transport them to the side of the single crystal furnace for the second feeding. The feeding interval for each cylinder is 60 min; During the first addition, 102.13 g of phosphorus-doped master alloy also needs to be added to the cylinder; S5. Start crystal pulling: Pull a complete N-type single crystal rod through the processes of seeding, shoulder expansion, shoulder rotation, equal diameter growth, tailing, and segment extraction. This N-type single crystal rod is denoted as D1. After removing the N-type single crystal rod, start the second feeding; S6. Repeat steps S4 and S5 for 8 times. The N-type single crystal rods are sequentially denoted as D2, D3, D4, D5, D6, D7, and D8; S7. Final stage feeding: When feeding in the final stage, the usage ratio of N-type dense material to recycled material is 45:55. The N-type dense material is loaded at the bottom of the barrel, and the recycled material is loaded in the middle and at the top. After loading the materials, they are transported to the side of the single crystal furnace for feeding in the final stage. After the feeding is completed, single crystal pulling is carried out normally. This N-type single crystal rod is denoted as D9.

[0089] The following tests are carried out on the obtained single crystal rods as above. Cost calculation: Calculate using cost calculation software.

[0090] Ratio of minority carrier lifetime to resistance at the head: First, use the Sinton BCT-400 device (a device based on eddy current sensors and infrared photoconductivity method to directly measure the minority carrier lifetime and resistance of single crystal or polycrystalline silicon rods, with transient and quasi-steady state measurement modes. This device can detect the minority carrier lifetime and resistance in a depth range of 3 mm) to measure the minority carrier lifetime and resistance at the head of the single crystal silicon rod. Then, the ratio of minority carrier lifetime to resistance at the head = minority carrier lifetime at the head / resistance at the head, minority carrier lifetime at the head (μs), resistivity at the head (Ω·m), ratio of minority carrier lifetime to resistance at the head (μs / Ω·m).

[0091] Oxygen at the head: Use Fourier transform infrared spectroscopy to test the oxygen content at the head of the single crystal silicon rod. The device used is the Bruker oxygen and carbon tester, model: TENSORⅡ, oxygen at the head (ppma).

[0092] Carbon at the tail: Use Fourier transform infrared spectroscopy to test the carbon content at the tail of the single crystal silicon rod. The device used is the Bruker oxygen and carbon tester, model: TENSORⅡ, carbon at the tail (ppma).

[0093] Table 1

[0094] From the above table, it can be obtained that the usage cost of Example 1 is 35.91 yuan / kg, which is 7.92% lower than the cost of Comparative Example 1; the average value of the ratio of minority carrier lifetime to resistance at the head of the 9 single crystal silicon rods produced is 2.3% lower than the average value of Comparative Example 1, the average value of oxygen at the head is 0.10 ppma higher than the average value of Comparative Example 1, and the average value of carbon at the tail is 0.02 ppma higher than the average value of Comparative Example 1.

[0095] The silicon material usage cost of Example 2 is 35.78 yuan / kg, which is 8.26% lower than the cost of Comparative Example 1; the average value of the ratio of minority carrier lifetime to resistance at the head of the 9 single crystal silicon rods produced is 2.5% lower than the average value of Comparative Example 1, the average value of oxygen at the head is 0.12 ppma higher than the average value of Comparative Example 1, and the average value of carbon at the tail is 0.04 ppma higher than the average value of Comparative Example 1.

[0096] The cost of the silicon material formula in Example 3 is 36.13 yuan / kg, which is 7.35% lower than that of the control group; the average value of the head minority carrier lifetime resistance ratio of the 9 single-crystal silicon rods produced is 1.4% lower than the average value of Comparative Example 1, the average value of the head oxygen is 0.03 ppma higher than that of Comparative Example 1, and the tail carbon is 0.01 ppma higher than the control group.

[0097] The cost of the silicon material formula in Example 4 is 36.32 yuan / kg, which is 6.87% lower than that of the control group; the average value of the head minority carrier lifetime resistance ratio of the 9 single-crystal silicon rods produced is 2.1% lower than the average value of Comparative Example 1, the average content of the head oxygen is 0.09 ppma higher than that of Comparative Example 1, and the average content of the tail carbon is 0.02 ppma higher than that of Comparative Example 1.

[0098] The usage cost of the silicon material in Example 5 is 37.18 yuan / kg, which is 4.67% lower than that of the control group; the average value of the head minority carrier lifetime resistance ratio of the 9 single-crystal silicon rods produced is 0.5% lower than the average value of Comparative Example 1, the average content of the head oxygen is 0.02 ppma higher than that of Comparative Example 1, and the tail carbon is the same as the control group.

[0099] In summary, using the raw material composition of the present application can obtain single-crystal silicon rods with better quality while reducing production costs.

[0100] Prepare solar cells of the same model and type for the single-crystal silicon rods marked A12, B2, C2, and D2 above, and the solar cells are denoted as A cell, B cell, C cell, and D cell in sequence.

[0101] Test the photoelectric conversion efficiency and concentric circles of the above batteries, and the results are shown in Table 2.

[0102] Test of photoelectric conversion efficiency: 1. Preparation stage: Ensure that the test equipment (such as solar simulator, thermometer, irradiance meter, photometer, photovoltaic test instrument, etc.) is accurately calibrated, and place the component under standard test conditions.

[0103] 2. Test process: Use a light source (such as solar simulator, LED light source, xenon arc lamp, etc.) to simulate the standard light intensity, measure the current and voltage generated by the component when receiving light, and thus calculate the output power.

[0104] 3. Calculate the conversion efficiency: According to the calculation formula of the photoelectric conversion efficiency (Efficiency = Pout / Pin×100%), where Pout is the output power of the solar cell and Pin is the input power of the solar cell (i.e., the light power irradiated by the sun on the solar cell), calculate the photoelectric conversion efficiency.

[0105] Test of concentric circles: Use an infrared thermal imager to scan the surface of the battery chip, and identify the concentric rings according to the temperature distribution difference.

[0106] Table 2

[0107] From the above table, it can be obtained that the efficiency of Battery D and Battery C is 26.97%, and the concentric circle ratio is 0.2%. It can be found that replacing the N-type dense material with 30% P-type dense material in the furnace has no effect on the photoelectric conversion efficiency and the concentric circle ratio of the battery chips; the efficiency of Battery A and Battery B is 26.94%, and the concentric circle ratio is 0.2%. After the coral material is introduced, the efficiency decreases by 0.03%, which is within the range of the efficiency fluctuation of the battery production line and meets the requirements, and has no effect on the concentric circle ratio. Therefore, the performance of the battery chips prepared by using the raw material composition of the present application meets the requirements, and at the same time, the goal of reducing the use cost of silicon materials is achieved.

[0108] It should also be noted that the "some embodiments", "other embodiments", "embodiments", etc. mentioned in the present application refer to the specific features, structures or characteristics described in connection with the embodiments being included in at least one embodiment generally described in the present application. The same expression appearing in multiple places in the specification does not necessarily refer to the same embodiment. Further, when describing a specific feature, structure or characteristic in connection with any one embodiment, it is intended that the implementation of such feature, structure or characteristic in combination with other embodiments also falls within the scope of the present application.

[0109] In the above embodiments, the descriptions of the respective embodiments have their own focuses. For the parts not detailed in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0110] It should also be noted that the above are only the preferred embodiments of the present application, and do not limit the patent protection scope of the present application accordingly. Any equivalent structure or equivalent process transformation made by using the content of the specification and drawings of the present application, or directly or indirectly applied in other related technical fields, shall be equally included in the patent protection scope of the present application.

Claims

1. A composition for preparing N-type single crystal silicon rods, characterized in that: The composition includes a recycled material and a first silicon material, wherein the first silicon material includes at least two of an N-type dense material, a P-type dense material, and a coral material.

2. The composition according to claim 1, characterized in that Based on the total mass of the composition, the mass of the recycled material is 45wt%-60wt%, and the mass of the first silicon material is 40wt%-55wt%.

3. The composition according to claim 1 or 2, characterized in that The first silicon material is the coral material and the N-type dense material, In the composition, the mass ratio of the N-type dense material, the coral material and the recycled material is (15-25):(20-30):(45-60).

4. The composition according to claim 1 or 2, characterized in that The first silicon material is the P-type dense material and the N-type dense material, In the composition, the mass ratio of the N-type dense material, the P-type dense material and the recycled material is (10-20):(20-40):(45-60).

5. The composition according to claim 1 or 2, characterized in that The first silicon material is the P-type dense material and the coral material, The mass ratio of the P-type dense material, the coral material and the recycled material is (10-30):(15-35):(45-60).

6. The composition according to claim 1 or 2, characterized in that The first silicon material is the P-type dense material, the coral material and the N-type dense material, The mass ratio of the N-type dense material, the P-type dense material, the coral material and the recycled material is (1-10):(10-20):(15-25):(45-60).

7. A method for preparing an N-type single crystal silicon rod using the composition according to any one of claims 1 to 6, characterized in that: The following steps are involved: Providing a furnace body, wherein a crucible is arranged in the furnace body; After the composition and the master alloy are added into the crucible and the materials are smelted, the single crystal is pulled to obtain an N-type single crystal silicon rod.

8. The method according to claim 7, characterized in that When the composition includes coral material, the operation of adding the composition and the master alloy into the crucible and mixing the materials includes: Adding the initial charge and the master alloy into the crucible and melting the materials; When the initial charge and the master alloy begin to melt, adding the composition and the master alloy into the crucible; Wherein, the initial charge includes a recycled material and a second silicon material, and the second silicon material includes the N-type dense material and / or the P-type dense material.

9. The method according to claim 8, characterized in that The operation of adding the composition to the crucible comprises: The coral material is located at the bottom of the barrel.

10. The method according to any one of claims 7 to 9, characterized in that: The chemical material satisfies at least one of the following conditions: The temperature is 1300℃~1700℃; The pressure is 530 Pa-800 Pa.

11. The method according to claim 7 or 8, characterized in that: Also includes: Circulation preset step: the preset step is to add re-feed material and the master alloy into the crucible, and after the re-feed material is completely melted, pull the single crystal; the re-feed material is the composition.

12. The method according to claim 11, characterized in that The number of cycles of the preset steps is 6 to 10 times.

13. The method according to claim 8, characterized in that Also includes: Adding finishing material into the crucible and melting the material; After the finished material is completely melted, the single crystal is pulled, and the finished material includes the second silicon material and the recycled material.

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