Monocrystalline silicon rod, preparation method thereof, silicon wafer, solar cell and photovoltaic module

Abstract

The invention provides a silicon single crystal rod, a preparation method thereof, a silicon wafer, a solar cell and a photovoltaic module. The single crystal silicon rod comprises a doping element, the saturation solid solubility of the doping element is greater than or equal to 5E + 19cm <-3 >, and the doping concentration range of the doping element is 8E + 14cm <-3 > to 3E + 16cm <-3 >. The preparation method comprises the following steps: melting a silicon raw material to obtain molten silicon liquid, and keeping furnace pressure at an initial furnace pressure value in the melting process; the silicon liquid is doped, and the furnace pressure is increased to the maximum value of the furnace pressure while doping is carried out; and in the equal-diameter growth stage, the furnace pressure is controlled to decrease from the highest furnace pressure value until the initial furnace pressure value is reached. According to the silicon single crystal rod and the preparation method thereof, the silicon wafer, the solar cell and the photovoltaic module, the resistivity of the silicon single crystal rod and derivative products thereof can be more uniform and concentrated.

Description

[0001] This application was filed on May 31, 2024, with application number 202410693014.X, and the invention name is a divisional application of the invention patent application for "Single crystal silicon rod and preparation method thereof, silicon wafer, solar cell, photovoltaic module". Technical Field

[0002] The present application mainly relates to the photovoltaic field, and in particular to a single crystal silicon rod and a preparation method thereof, a silicon wafer, a solar cell, and a photovoltaic module. Background Art

[0003] Based on the emphasis on environmental protection, solar energy as a new type of clean energy has received extensive attention and development in recent years. At present, most solar cells use single-crystal silicon wafers as their raw materials. The cost and photoelectric conversion efficiency of single-crystal silicon wafers directly affect the development of these solar cells. At present, N-type solar single-crystal silicon wafers are often doped with phosphorus. The doping of phosphorus will have a certain impact on the optical properties of single-crystal silicon materials, such as absorption, transparency and refractive index. For example, the doping of phosphorus will reduce the absorption rate of single-crystal silicon materials. Summary of the invention

[0004] The technical problem to be solved by the present application is to provide a single crystal silicon rod and a preparation method thereof, as well as a silicon wafer, a solar cell, and a photovoltaic module, which can make the resistivity of the single crystal silicon rod and its derivative products more uniform and concentrated.

[0005] In order to solve the above technical problems, the present application provides a single crystal silicon rod, wherein the single crystal silicon rod includes a doping element, and the saturated solid solubility of the doping element is greater than or equal to 5E+19cm -3 , and the doping concentration range of the doping element is 8E+14cm -3 To 3E+16cm -3 .

[0006] Optionally, the doping element in the single crystal silicon rod is formed by doping a silicon raw material including single crystal silicon through a gas phase doping method or a solid phase doping method.

[0007] Optionally, the doping element includes arsenic or antimony, and the dopant used in the preparation of the single crystal silicon rod includes elemental antimony, elemental arsenic and / or arsenic-containing compounds, wherein the arsenic-containing compounds include gallium arsenic and / or arsenic oxide.

[0008] Optionally, the resistivity of the single crystal silicon rod is in the range of 0.3Ω·cm to 3Ω·cm.

[0009] Optionally, during the isodiameter growth stage, the head resistivity R x and tail resistivity R Y The following conditions are met:

[0010]

[0011] Among them, Y and X are arbitrary equal diameter growth lengths, both in mm.

[0012] Another aspect of the present application provides a method for preparing a single crystal silicon rod, comprising the following steps: melting a silicon raw material to obtain a molten silicon liquid, and during the melting process, maintaining the furnace pressure at an initial furnace pressure value; doping the silicon liquid, and while performing the doping, increasing the furnace pressure to a maximum furnace pressure value; and in the equal-diameter growth stage, controlling the furnace pressure to decrease from the maximum furnace pressure value until it reaches the initial furnace pressure value.

[0013] Optionally, the preparation method also includes the following steps: during the melting process, maintaining the argon gas flow rate at the initial argon gas flow rate; while performing the doping, reducing the argon gas flow rate to a minimum argon gas flow rate; and during the equal-diameter growth stage, controlling the argon gas flow rate to increase from the minimum argon gas flow rate until reaching the initial argon gas flow rate.

[0014] Optionally, the step of controlling the argon gas flow rate to increase from the minimum argon gas value further includes controlling the argon gas flow rate to increase in the following manner:

[0015]

[0016] Among them, Q1 is the argon flow rate corresponding to the growth of the single crystal silicon rod to any equal-diameter growth length, and the unit is slpm; Q0 is the argon flow rate at the initial moment of the equal-diameter growth stage, and the unit is slpm; |ΔL| is the absolute value of the difference between two arbitrary growth lengths of the single crystal silicon rod in the equal-diameter growth stage, and the unit is mm; x is a constant parameter, and the value of x is 0.5~2.

[0017] Optionally, the preparation method also includes: after the single crystal silicon rod enters the equal-diameter growth stage, controlling the temperature in the furnace to increase by 0.3°C to 1°C for every 500mm growth of the single crystal silicon rod; and when the equal-diameter growth length is greater than or equal to 2000mm, controlling the temperature in the furnace to increase by 0.3°C to 0.5°C for every 500mm growth of the single crystal silicon rod.

[0018] Optionally, the preparation method further comprises increasing the crucible rotation parameter from 4 r / min to 6 r / min when the equal-diameter growth length is greater than or equal to 2000 mm.

[0019] Optionally, the preparation method further comprises reducing the furnace power by 0.4 kW to 0.6 kW while increasing the crucible rotation parameter from 4 rpm to 6 rpm.

[0020] Optionally, the step of doping the silicon liquid in the preparation method further comprises doping the silicon liquid with a doping element, wherein the saturated solid solubility of the doping element is greater than or equal to 5E+19cm -3 , and the doping concentration range of the doping element is 8E+14cm -3 To 3E+16cm -3 .

[0021] Optionally, the doping element in the preparation method includes antimony or arsenic.

[0022] Optionally, the preparation method further comprises reducing the furnace pressure to the initial furnace pressure value when the single crystal silicon rod grows to 70-80% of the total growth length of the single crystal silicon rod in the equal diameter growth stage.

[0023] Another aspect of the present application further provides a single crystal silicon rod, which is prepared according to the preparation method described in any embodiment of the present application.

[0024] Another reverse side of the present application also provides a silicon wafer, which is prepared from the single crystal silicon rod according to any embodiment of the present application.

[0025] Another aspect of the present application also provides a solar cell, which is prepared from the silicon wafer according to any embodiment of the present application.

[0026] Another reverse side of the present application also provides a photovoltaic assembly, comprising a plurality of solar cells provided in any embodiment of the present application connected in series and / or in parallel.

[0027] Compared with the prior art, the present application has the following advantages: the present application can make the resistivity of the single crystal silicon rod uniform and concentrated by providing the selection of doping elements with excellent performance and the configuration of the doping concentration; at the same time, it provides an adapted method for preparing the single crystal silicon rod, which can further enhance and optimize the effect of uniform and concentrated resistivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The accompanying drawings are included to provide a further understanding of the present application. They are included and constitute a part of the present application. The accompanying drawings illustrate embodiments of the present application and together with the present specification serve to explain the principles of the present application. In the accompanying drawings:

[0029] Figure 1 It is a schematic flow chart of a method for preparing a single crystal silicon rod according to an embodiment of the present application. DETAILED DESCRIPTION

[0030] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for the description of the embodiments. Obviously, the drawings described below are only some examples or embodiments of the present application. For ordinary technicians in this field, the present application can also be applied to other similar scenarios based on these drawings without creative work. Unless it is obvious from the language environment or otherwise explained, the same reference numerals in the figures represent the same structure or operation.

[0031] As shown in this application and claims, unless the context clearly indicates an exception, the words "a", "an", "an" and / or "the" do not refer to the singular and may also include the plural. Generally speaking, the terms "include" and "comprise" only indicate the inclusion of the steps and elements that have been clearly identified, and these steps and elements do not constitute an exclusive list. The method or device may also include other steps or elements.

[0032] Unless otherwise specifically stated, the relative arrangement, numerical expressions and numerical values ​​of the parts and steps set forth in these embodiments do not limit the scope of the present application. At the same time, it should be understood that, for ease of description, the sizes of the various parts shown in the accompanying drawings are not drawn according to the actual proportional relationship. The technology, method and equipment known to those of ordinary skill in the relevant field may not be discussed in detail, but in appropriate cases, the technology, method and equipment should be considered as a part of the authorization specification. In all examples shown and discussed here, any specific value should be interpreted as being merely exemplary, rather than as a limitation. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters represent similar items in the following drawings, so that once a certain item is defined in an accompanying drawing, it does not need to be further discussed in subsequent drawings.

[0033] In the description of the present application, it should be understood that the directions or positional relationships indicated by directional words such as "front, back, up, down, left, right", "lateral, vertical, perpendicular, horizontal" and "top, bottom" are usually based on the directions or positional relationships shown in the drawings, and are only for the convenience of describing the present application and simplifying the description. Unless otherwise specified, these directional words do not indicate or imply that the device or element referred to must have a specific direction or be constructed and operated in a specific direction, and therefore cannot be understood as limiting the scope of protection of the present application; the directional words "inside and outside" refer to the inside and outside relative to the contours of each component itself.

[0034] For ease of description, spatially relative terms such as "above", "above", "on the upper surface of", "above", etc. may be used here to describe the spatial positional relationship between a device or feature and other devices or features as shown in the figure. It should be understood that spatially relative terms are intended to include different orientations of the device in use or operation in addition to the orientation described in the figure. For example, if the device in the accompanying drawings is inverted, the device described as "above other devices or structures" or "above other devices or structures" will be positioned as "below other devices or structures" or "below other devices or structures". Thus, the exemplary term "above" can include both "above" and "below". The device can also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatially relative descriptions used here are interpreted accordingly.

[0035] In addition, it should be noted that the use of words such as "first" and "second" to define components is only for the convenience of distinguishing the corresponding components. If not otherwise stated, the above words have no special meaning and cannot be understood as limiting the scope of protection of this application. In addition, although the terms used in this application are selected from well-known and commonly used terms, some terms mentioned in the specification of this application may be selected by the applicant at his or her discretion, and their detailed meanings are explained in the relevant parts of the description of this article. In addition, it is required to understand this application not only by the actual terms used, but also by the meaning implied by each term.

[0036] It should be understood that when a component is referred to as being "on another component," "connected to another component," "coupled to another component," or "contacting another component," it may be directly on, connected to, coupled to, or contacting the other component, or there may be intervening components. In contrast, when a component is referred to as being "directly on another component," "directly connected to," "directly coupled to," or "directly contacting" another component, there are no intervening components. Similarly, when a first component is referred to as being "electrically in contact with" or "electrically coupled to" a second component, there is an electrical path between the first component and the second component that allows current to flow. The electrical path may include capacitors, coupled inductors, and / or other components that allow current to flow, even without direct contact between conductive components.

[0037] One embodiment of the present application provides a single crystal silicon rod, wherein the single crystal silicon rod includes a doping element, wherein the saturated solid solubility of the doping element is greater than or equal to 5E+19cm -3 , and the doping concentration range of the doping element is 8E+14cm -3 To 3E+16cm -3Further preferably, the concentration range can be set at 2.5E+15cm -3 To 1.85E+16cm -3 , or further 2.95E+15cm -3 To 1.55E+16cm -3 In between, a single crystal silicon rod with better effect can be obtained.

[0038] In this embodiment, by controlling the doping concentration of the doping element, different corresponding preferred resistivity ranges can be obtained. For example, when the doping concentration range of the doping element is 8E+14cm -3 To 3E+16cm -3 When the resistivity of the single crystal silicon rod is preferably in the range of 0.3Ω·cm to 3Ω·cm; further, when the doping concentration of the doping element is in the range of 2.5E+15cm -3 To 1.85E+16cm -3 When the resistivity of the single crystal silicon rod is preferably in the range of 0.3Ω·cm to 2Ω·cm; when the doping concentration of the doping element is in the range of 2.95E+15cm -3 To 1.55E+16cm -3 When the resistivity of the single crystal silicon rod is preferably obtained in the range of 0.4Ω·cm to 1.6Ω·cm.

[0039] Exemplarily, the doping element in the single crystal silicon rod in this embodiment is formed by doping a silicon raw material including single crystal silicon by a gas phase doping method or a solid phase doping method. Further preferably, the doping element includes arsenic or antimony, and the dopant in the preparation process of the single crystal silicon rod includes elemental antimony, elemental arsenic and / or an arsenic-containing compound, wherein the arsenic-containing compound includes gallium arsenic and / or arsenic oxide.

[0040] By controlling the doping concentration of the doping element, under the premise of obtaining the target resistivity range, in this embodiment, preferably, the single crystal silicon rod has a specific resistivity change requirement in the equal diameter growth stage, so that the resistivity of the single crystal silicon rod finally obtained is uniform and concentrated. Preferably, in this embodiment, in the equal diameter growth stage, the head resistivity R x and tail resistivity R Y The following conditions are met:

[0041]

[0042] Among them, Y and X are arbitrary equal-diameter growth lengths, and the unit is mm. Specifically, in a specific embodiment, YX is the difference between two equal-diameter growth lengths, and the difference is 100mm, for example, Y=1000mm, X=900mm. However, the present application is not limited to this, and YX can also be arbitrarily selected between greater than 100mm and less than 100mm, preferably YX<100mm, in which case a single crystal silicon rod with a more uniform resistivity distribution can be obtained. Further preferably, the end values ​​of the above-mentioned rate-of-change related parameters can be further narrowed, for example:

[0043]

[0044] By controlling the resistivity change rate of the single crystal silicon rod after the crystal rod grows to a fixed length of 100 mm within a certain range, the resistivity distribution of the single crystal silicon rod can be made more uniform and concentrated.

[0045] Compared with the prior art, the single crystal silicon rods in the above-mentioned embodiments of the present application can obtain single crystal silicon rods with a more uniform and concentrated resistivity distribution by selecting doping elements in a specific saturated solid solubility range and controlling the doping concentration in the single crystal silicon rods. Taking arsenic (As) as an example, arsenic has the characteristics of high solubility in silicon solution, low mismatch with silicon, low segregation coefficient, and high volatility. As a dopant for solar-grade single crystal silicon, single crystal silicon rods with uniform resistivity can be obtained, making the single crystal silicon rods highly efficient and highly utilized. Arsenic has a high solubility in silicon, and the maximum value can reach 9E+19cm -3 , this value is three times higher than the solubility of phosphorus (P). At the same time, the segregation coefficient of arsenic k (As) is 0.3, which is lower than the segregation coefficient of phosphorus k (P) = 0.34, and can have a smaller axial resistance gap. At the same time, the atomic radius of arsenic is similar to that of silicon, and the mismatch with silicon is low, which brings about small lattice distortion, resulting in a high crystallization rate in the production process. Therefore, the above embodiment proposes that arsenic can be used as a doping element for solar energy high-efficiency single crystals. While controlling the high-efficiency silicon wafer to have an excellent resistivity range, by optimizing the doping concentration of arsenic, a single crystal silicon rod with a better resistivity range is obtained, which can be further processed into more efficient solar single crystal silicon wafers, solar cells and photovoltaic modules, thereby improving the energy conversion efficiency of solar cells. On the other hand, the saturated solid solubility of antimony in silicon is 5E+19cm -3 , and its segregation coefficient is k(Sb)=0.023. By controlling its doping concentration within a suitable range, a single crystal silicon rod with uniform and concentrated resistivity distribution can also be achieved.

[0046] The production process of single crystal silicon consists of several steps such as melt, doping, temperature adjustment, welding, seeding, shoulder release, shoulder rotation, equal diameter, and finishing. Specifically, the melt step is to melt the silicon raw material, and the doping step is to add doping elements to the molten silicon liquid under the premise of certain temperature adjustment. Further, the temperature adjustment step involves adjusting the process temperature to the process temperature applicable to the subsequent seeding step. Exemplarily, for some doping elements (such as arsenic or antimony), the following temperature and power control means are applicable in the preparation method to be introduced later in this application: doping is performed after the melt is finished, and the temperature is initially adjusted to the doping temperature after the melt is finished. The doping temperature is set to be 20℃-30℃ lower than the seeding temperature, and the power is set to be 1KW-3KW lower than the seeding power, and then the temperature adjustment process is performed. After the end, the temperature is stabilized for 0.5h-1h, and then doping is started. Further, the crystal pulling process includes a combination of seeding, shoulder release, shoulder rotation, equal diameter, and finishing. The crystal pulling conditions are generally affected by process parameters such as temperature, pulling speed, argon flow rate, furnace pressure, crystal rotation, crucible rotation, etc. This application proposes a method of improving product quality by adjusting the change control strategy of process parameters.

[0047] Also for the purpose of making the resistivity of the single crystal silicon rod more uniform and concentrated, another aspect of the present application refers to Figure 1 A method for preparing a single crystal silicon rod is proposed. Figure 1 Flowcharts are used to illustrate the operations performed by the system according to the embodiments of the present application. It should be understood that the preceding or following operations are not necessarily performed precisely in order. Instead, various steps may be processed in reverse order or simultaneously. At the same time, other operations may be added to these processes, or one or more operations may be removed from these processes.

[0048] according to Figure 1 , the preparation method 10 includes the following steps. Step 11 is to melt the silicon raw material to obtain molten silicon liquid, and during the melting process, the furnace pressure is maintained at the initial furnace pressure value. Step 12 is to dope the silicon liquid, and while doping, the furnace pressure is increased to the maximum furnace pressure value. Step 13 is to control the furnace pressure to decrease from the maximum furnace pressure value during the equal-diameter growth stage until the initial furnace pressure value is reached. Exemplarily, if the initial furnace pressure value is the lowest furnace pressure value during the overall preparation process of the single crystal silicon rod, the above process can also be understood as a process in which the furnace pressure is increased from the lowest furnace pressure value to the highest furnace pressure value during the doping process, and then the furnace pressure is decreased from the highest furnace pressure value to the lowest furnace pressure value during the equal-diameter growth stage.

[0049] Exemplarily, in the above step 13, with respect to the control method of controlling the furnace pressure to drop from the maximum furnace pressure value until the initial furnace pressure value is reached, the present application does not restrict whether the furnace pressure is dropped evenly. However, based on the preparation method 10, preferably, some embodiments of the present application can achieve better preparation results by controlling the moment when the furnace pressure drops to the initial furnace pressure value in correlation with the equal-diameter growth length. Preferably, when the single crystal silicon rod grows to 70-80% of the total growth length of the single crystal silicon rod in the equal-diameter growth stage, the furnace pressure is reduced to the initial furnace pressure value.

[0050] Table 1 below is the comparison information of an exemplary furnace pressure change control strategy of the present application. Specifically, controlling the furnace pressure during the doping stage and the specific furnace pressure values ​​corresponding to different equal-diameter growth lengths during the equal-diameter growth process can achieve better preparation results.

[0051]

[0052]

[0053] Table 1

[0054] According to Table 1, it can be seen that from the melting stage to the final finishing stage, the overall range of the furnace pressure of the furnace is controlled within the range of 7torr to 20torr. The specific adjustment method is that during the melting process, the initial furnace pressure value of the furnace pressure is 7torr, the furnace pressure is increased to the maximum furnace pressure value of 20torr in the doping stage, and the furnace pressure of the furnace is further gradually reduced in the equal-diameter growth stage as the crystal grows. Preferably, referring to Table 1, the furnace pressure of the furnace in the doping stage increases from 7torr in the melting stage to 20torr, and continues until the early stage of the equal-diameter growth stage. When the equal-diameter growth length is between 500mm and 1000mm, the furnace pressure gradually decreases as the equal-diameter growth length increases; preferably, when the equal-diameter growth length is between 800mm and 1000mm, the furnace pressure is controlled to start decreasing; until the equal-diameter growth length reaches 2000mm, the furnace pressure has been reduced to 7torr, and the furnace pressure continues to be maintained at 7torr in the finishing stage. It can be seen from the embodiments shown in Table 1 that, assuming that the total length of the equal-diameter growth of the crystal is 3000 mm, the furnace pressure is controlled to be reduced to the initial furnace pressure value between 70% and 80% of the total length, that is, when the equal-diameter growth length is between 2000 mm and 2500 mm, it is reduced to the initial furnace pressure value of 7 torr, thereby achieving a better growth effect.

[0055] Further preferably, while controlling the change in furnace pressure, another embodiment of the present application also adds a parameter control strategy for controlling the argon gas flow rate, so as to obtain a better single crystal silicon rod growth effect. Specifically, the control strategy for the argon gas flow rate is as follows: first, during the melting process, the argon gas flow rate is maintained at the initial argon gas flow rate; further, while doping, the argon gas flow rate is reduced to the minimum argon gas flow rate; and in the isodiameter growth stage, the argon gas flow rate is controlled to increase from the minimum argon gas flow rate until it reaches the initial argon gas flow rate.

[0056] More preferably, the step of controlling the argon flow rate to increase from the minimum argon flow rate further includes controlling the argon flow rate to increase in the following manner:

[0057]

[0058] Among them, Q1 is the argon flow rate corresponding to the growth of the single crystal silicon rod to any equal-diameter growth length, in slpm; Q0 is the argon flow rate at the initial moment of the equal-diameter growth stage, in slpm; |ΔL| is the absolute value of the difference between two arbitrary growth lengths of the single crystal silicon rod in the equal-diameter growth stage, in mm; x is a constant parameter, and the value of x is 0.5~2.

[0059] Table 2 below is the comparison information of an exemplary argon flow rate change control strategy of the present application. Specifically, controlling the specific argon flow rate corresponding to different equal-diameter growth lengths during the doping stage and the equal-diameter growth process can achieve better preparation results.

[0060] Process stage Argon flow rate Melting stage 100slpm Doping stage 75slpm Equal diameter growth length 500mm 75slpm Equal diameter growth length 1000mm 80slpm Equal diameter growth length 1500mm 85slpm Equal diameter growth length 2000mm 90slpm Equal diameter growth length 2500mm 95slpm Equal diameter growth length 3000mm 100slpm Closing Stage 100slpm

[0061] Table 2

[0062] According to Table 2, the argon flow rate change control strategy is specifically implemented as adjusting the argon flow rate of the furnace as the silicon single crystal grows. The specific adjustment method is to open the maximum argon flow rate of 100slpm in the melting stage, with the aim of reducing the concentration of oxygen impurities as much as possible in the melting stage. Further, the argon flow rate is adjusted to a minimum value of 75slpm in the doping stage, and after entering the equal-diameter generation stage, the argon flow rate is gradually increased as the equal-diameter growth length increases. Preferably, the change control strategy of the argon flow rate in the equal-diameter stage in this embodiment can be expressed by the following formula:

[0063]

[0064] Among them, Q1 is the argon flow rate corresponding to the growth of the single crystal silicon rod to any equal-diameter growth length, in slpm; Q0 is the argon flow rate at the initial moment of the equal-diameter growth stage, specifically 75 slpm; |ΔL| is the absolute value of the difference between two arbitrary growth lengths of the single crystal silicon rod in the equal-diameter growth stage. For example, in this embodiment, the value of |ΔL| is 500mm, that is, the corresponding argon flow rate is indicated for every 500mm interval of equal-diameter growth length reflected in the table. In this embodiment, x is a constant parameter and its value is 1, that is, referring to Table 2, for every 500mm increase in the equal-diameter growth length, the argon flow rate increases by 5 slpm. Of course, the present application is not limited to the above-mentioned changes in the argon flow rate. Table 2 only schematically indicates one of the methods that conforms to the argon flow control strategy of the present application.

[0065] On the other hand, the argon flow rate change control strategy shown in Table 2 can also be combined with the furnace pressure change control strategy shown in Table 1. At any given moment corresponding to the equal-diameter growth length, the furnace pressure and the argon flow rate can be set as target values ​​at the same time, so as to obtain a better preparation effect. Specifically, in the equal-diameter growth stage, for volatile doping elements, since it is hoped to minimize the reduction of doping elements during the crystallization process, which will affect the uniformity of resistivity, it is hoped to increase the volatilization rate of doping elements during the equal-diameter growth stage. As for the furnace pressure change control strategy, the lower the furnace pressure, the greater the power of the vacuum pump for extracting argon gas. Under the same argon flow rate, the air flow rate of the furnace table increases accordingly, thereby increasing the volatilization rate of the doping elements, thereby achieving a better resistivity change result. Therefore, when the furnace pressure and argon flow rate change control strategies are combined with each other, a better preparation effect can be achieved.

[0066] Further preferably, in some other embodiments of the present application, after the single crystal silicon rod enters the equal-diameter growth stage, a strategy for temperature change control is also included. Preferably, in one embodiment, after the single crystal silicon rod enters the equal-diameter growth stage, the temperature in the furnace is controlled to rise by 0.3°C to 1°C for every 500mm growth of the single crystal silicon rod. Further, when the equal-diameter growth length is greater than or equal to 2000mm, the temperature in the furnace is controlled to rise by 0.3°C to 0.5°C for every 500mm growth of the single crystal silicon rod. Specifically, after the temperature rises, the pulling speed of the crystal pulling process is reduced, and the crystallization effect is better. On the other hand, with reference to the embodiments shown in Tables 1 and 2 above, the temperature change control strategy can also be combined with the embodiments of Tables 1 and / or 2, specifically, when the equal-diameter growth length is not greater than 2000mm, a wider range of change rates is used to increase the temperature in the furnace, and after the equal-diameter growth length reaches 2000mm, that is, after entering the late stage of the equal-diameter growth stage, the rate at which the temperature in the furnace rises is slowed down.

[0067] On the other hand, in another preferred embodiment of the present application, a control strategy for the change of the crucible rotation parameter is also included, specifically, when the equal diameter growth length is greater than or equal to 2000mm, the crucible rotation parameter is increased from 4r / min to 6r / min. Further preferably, while increasing the crucible rotation parameter from 4r / min to 6r / min, the furnace power is reduced by 0.4kw to 0.6kw, preferably 0.5kw. Specifically, the larger the crucible rotation parameter, the greater the convection of the liquid in the crucible, the temperature uniformity of the silicon liquid is improved, and the volatilization rate of the doping element is further improved, thereby obtaining a better resistivity.

[0068] At the same time, the control strategy for the change of the crucible rotation parameter can be combined with the embodiments of Table 1 and / or Table 2, and of course, it can also be further combined with the above-mentioned strategy for temperature change control. Preferably, when combined with the strategy of temperature change control, the following scheme can be adopted: when the single crystal silicon rod enters the equal diameter growth stage, the temperature in the furnace is controlled to increase by 0.3°C to 1°C for every 500mm growth of the single crystal silicon rod, while keeping the crucible rotation parameter unchanged. Further, when the equal diameter growth length is greater than or equal to 2000mm, the single crystal silicon rod grows 500mm, and only the crucible rotation parameter is increased from 4r / min to 6r / min, or the furnace power is further reduced by 0.4kw to 0.6kw, and the temperature is no longer increased. This is to consider that after the equal diameter growth rate reaches 2000mm, since increasing the value of the crucible rotation parameter and increasing the temperature have the same effect of reducing the pulling speed, in order to avoid affecting the overall preparation output of the single crystal silicon rod, in the later stage of the equal diameter growth stage, it is preferred to only use the method of increasing the crucible rotation parameter for regulation, so as to achieve a better preparation effect.

[0069] In any of the above embodiments of the preparation method of the present application, the step of doping the silicon liquid further includes doping the silicon liquid with a doping element, wherein the saturated solid solubility of the doping element is greater than or equal to 5E+19cm -3 , and the doping concentration range of the doping element is 8E+14cm -3 To 3E+16cm -3 Preferably, the doping element is antimony or arsenic. By controlling the doping concentration of a specific doping element and matching the corresponding preferred process parameter change control strategy, a more optimal single crystal silicon rod with concentrated and uniform resistivity change can be prepared.

[0070] Taking arsenic as an example, since the segregation coefficient of arsenic is less than 1, the concentration of doping elements in the residual material will gradually increase during the crystal pulling process, causing the resistivity of the crystal rod to gradually decrease with the increase of the length of the crystal rod. Due to its volatile nature, arsenic is often doped after the melt is finished. However, since the doping concentration of single crystal silicon used in solar cells is low, the volatilization effect of arsenic is weak. During the production process, volatilization will occur, changing the doping concentration of the residual material and affecting the resistivity of the crystal rod. Therefore, by setting appropriate process parameters, the volatilization degree of the dopant can be affected, ensuring the uniformity of the axial resistance of the crystal rod, and obtaining high-efficiency arsenic-doped single crystals, which is of great significance for the production of arsenic-doped single crystal silicon for solar energy. Exemplarily, the change control strategy of the above-mentioned process parameters can also be cited in the process flow of doping antimony elements, which can also achieve better preparation effects.

[0071] Table 3 shown below shows the comparative test results of the four specific embodiments 1 to 4 of the present application and the comparative examples. Table 3 shows the corresponding resistivity values ​​(Ω·cm) under different equal diameter lengths of 1000mm, 1500mm, 2000mm, 2500mm and 3000mm in embodiments 1 to 4 and the comparative examples. Among them, embodiments 1 to 4 combine the embodiments of Table 1 and Table 2 above as well as the temperature change control strategy and the crucible rotation parameter change control strategy. Specifically, the comparative example adopts the process parameters in the general sense of on-site production, including a constant furnace pressure of 10ttor, a constant argon flow rate of 100slpm, a constant temperature, and a crucible rotation parameter control of 4 rpm, and a crystal rotation control of 10 rpm. Each embodiment related to the present application and the comparative example adopt the same arsenic doping concentration of 1.45×10 16 cm -3 . Further, Example 1 is a scheme that only implements the furnace pressure change control strategy shown in Table 1, and other process parameters refer to the comparative example. Example 2 implements the argon flow change control strategy shown in Table 2, and other process parameters refer to Example 1. Example 3 implements the temperature change control strategy, and other process parameters refer to Example 2. Example 4 implements the crucible rotation parameter change control strategy, and other process parameters refer to Example 3.

[0072]

[0073] Table 3

[0074] As can be seen from Table 3 above, in each of Examples 1 to 4 of the present application, by respectively introducing furnace pressure, argon flow rate, temperature and crucible transfer parameter change control strategies, the resistivity change per 100 mm is controlled below 1.5%, which is much less than 2.750% of the comparative example, and the resistivity uniformity and concentration are significantly improved. On the other hand, in Examples 1 to 4, due to the sequential superposition of different process parameter change control strategies, Examples 2 and 4 show a smaller resistivity change trend, which means that the simultaneous implementation of the furnace pressure and argon flow change control strategy and the simultaneous implementation of the furnace pressure, argon flow rate, temperature and crucible transfer parameter change control strategy are slightly better than the simultaneous implementation of the furnace pressure, argon flow rate and temperature change control strategy in the final resistivity change result. In practical applications, those skilled in the art can combine the specific preparation conditions and other preparation requirements to comprehensively select the combination of the adopted process parameter change control strategy, and the present application does not limit this.

[0075] Another aspect of the present application is to propose a single crystal silicon rod, which is prepared according to the preparation method proposed in any embodiment of the present application. On this basis, the present application also proposes a silicon wafer, a solar cell and a photovoltaic module according to the preferred doping concentration and the preparation method, wherein the photovoltaic module includes a plurality of solar cells proposed in the present application connected in series and / or in parallel. For silicon wafers, solar cells and photovoltaic modules, since their raw materials use the single crystal silicon rods prepared by the preferred differential doping concentration and preparation method proposed in the present application, they have good resistivity characteristics and good photoelectric conversion efficiency.

[0076] The basic concepts have been described above. Obviously, for those skilled in the art, the above application disclosure is only an example and does not constitute a limitation of the present application. Although not explicitly stated herein, those skilled in the art may make various modifications, improvements and amendments to the present application. Such modifications, improvements and amendments are suggested in the present application, so such modifications, improvements and amendments still belong to the spirit and scope of the exemplary embodiments of the present application.

[0077] At the same time, the present application uses specific words to describe the embodiments of the present application. For example, "one embodiment", "an embodiment", and / or "some embodiments" refer to a certain feature, structure or characteristic related to at least one embodiment of the present application. Therefore, it should be emphasized and noted that "one embodiment" or "an embodiment" or "an alternative embodiment" mentioned twice or more in different positions in this specification does not necessarily refer to the same embodiment. In addition, some features, structures or characteristics in one or more embodiments of the present application can be appropriately combined.

[0078] Similarly, it should be noted that in order to simplify the description of the disclosure of this application and thus help understand one or more application embodiments, in the above description of the embodiments of this application, multiple features are sometimes merged into one embodiment, figure or description thereof. However, this disclosure method does not mean that the features required by the object of this application are more than the features mentioned in the claims. In fact, the features of the embodiments are less than all the features of the single embodiment disclosed above.

[0079] In some embodiments, numbers describing the number of components and attributes are used. It should be understood that such numbers used in the description of the embodiments are modified by the modifiers "about", "approximately" or "substantially" in some examples. Unless otherwise specified, "about", "approximately" or "substantially" indicate that the numbers are allowed to vary by ±20%. Accordingly, in some embodiments, the numerical parameters used in the specification and claims are approximate values, which may change according to the required features of individual embodiments. In some embodiments, the numerical parameters should take into account the specified significant digits and adopt the general method of retaining digits. Although the numerical domains and parameters used to confirm the breadth of their range in some embodiments of the present application are approximate values, in specific embodiments, the setting of such numerical values ​​is as accurate as possible within the feasible range.

[0080] Although the present application has been described with reference to the current specific embodiments, ordinary technicians in this technical field should recognize that the above embodiments are only used to illustrate the present application, and various equivalent changes or substitutions may be made without departing from the spirit of the present application. Therefore, as long as the changes and modifications to the above embodiments are within the essential spirit of the present application, they will fall within the scope of the claims of the present application.

Claims

1. A single crystal silicon rod, characterized in that: The single crystal silicon rod includes a doping element, and the saturated solid solubility of the doping element is greater than or equal to 5E+19cm -3 , and the doping concentration range of the doping element is 8E+14cm -3 To 3E+16cm -3 . The single crystal silicon rod is in the equal diameter growth stage, and the head resistivity R x and tail resistivity R Y The following conditions are met: Among them, Y and X are arbitrary equal diameter growth lengths, both in mm.

2. The single crystal silicon rod according to claim 1, characterized in that: The doping elements in the single crystal silicon rod are formed by doping silicon raw materials including single crystal silicon through a gas phase doping method or a solid phase doping method.

3. The single crystal silicon rod according to claim 1, characterized in that: The doping element includes arsenic or antimony, and the dopant used in the preparation of the single crystal silicon rod includes elemental antimony, elemental arsenic and / or arsenic-containing compounds, wherein the arsenic-containing compounds include gallium arsenic and / or arsenic oxide.

4. The single crystal silicon rod according to claim 1, characterized in that: The resistivity of the single crystal silicon rod is in the range of 0.3Ω·cm to 3Ω·cm.

5. A method for preparing a single crystal silicon rod, characterized in that: The steps include: Melting the silicon raw material to obtain molten silicon liquid, and during the melting process, maintaining the furnace pressure at an initial furnace pressure value; Doping the silicon liquid, and while doing so, increasing the furnace pressure to a maximum furnace pressure value; as well as During the isodiameter growth stage, the furnace pressure is controlled to decrease from the maximum furnace pressure value until it reaches the initial furnace pressure value.

6. The preparation method according to claim 5, characterized in that: The following steps are also included: During the melting process, maintaining the argon gas flow rate at the initial argon gas flow rate; While performing the doping, reducing the argon gas flow rate to a minimum argon gas flow rate; as well as During the equal-diameter growth stage, the argon flow rate is controlled to increase from the minimum argon flow rate until it reaches the initial argon flow rate.

7. The preparation method according to claim 6, characterized in that: The step of controlling the argon gas flow rate to increase from the argon gas minimum value further includes controlling the argon gas flow rate to increase in the following manner: Among them, Q1 is the argon flow rate corresponding to the growth of the single crystal silicon rod to any equal-diameter growth length, and the unit is slpm; Q0 is the argon flow rate at the initial moment of the equal-diameter growth stage, and the unit is slpm; |ΔL| is the absolute value of the difference between two arbitrary growth lengths of the single crystal silicon rod in the equal-diameter growth stage, and the unit is mm; x is a constant parameter, and the value of x is 0.5~2.

8. The preparation method according to claim 5, characterized in that: Also includes: After the single crystal silicon rod enters the equal diameter growth stage, the temperature in the furnace is controlled to increase by 0.3° C. to 1° C. for every 500 mm growth of the single crystal silicon rod; as well as When the equal-diameter growth length is greater than or equal to 2000 mm, the temperature in the furnace is controlled to increase by 0.3° C. to 0.5° C. every time the single crystal silicon rod grows 500 mm.

9. The preparation method according to claim 5, characterized in that: The method also includes increasing the crucible rotation parameter from 4 r / min to 6 r / min when the equal diameter growth length is greater than or equal to 2000 mm.

10. The preparation method according to claim 9, characterized in that: The method also includes reducing the furnace power by 0.4 kW to 0.6 kW while increasing the crucible rotation parameter from 4 rpm to 6 rpm.

11. The preparation method according to claim 5, characterized in that: The step of doping the silicon liquid further comprises doping the silicon liquid with a doping element, wherein the saturated solid solubility of the doping element is greater than or equal to 5E+19cm -3 , and the doping concentration range of the doping element is 8E+14cm -3 To 3E+16cm -3 .

12. The preparation method according to claim 11, characterized in that: The doping element includes antimony or arsenic.

13. The preparation method according to any one of claims 5 to 12, characterized in that: The method further includes reducing the furnace pressure to the initial furnace pressure value when the single crystal silicon rod grows to 70-80% of the total growth length of the single crystal silicon rod in the equal diameter growth stage.

14. A single crystal silicon rod, characterized in that: The single crystal silicon rod is prepared according to the preparation method according to any one of claims 5 to 13.

15. A silicon wafer, characterized in that: It is prepared according to the single crystal silicon rod according to any one of claims 1 to 4, or prepared according to the single crystal silicon rod according to claim 14.

16. A solar cell, characterized in that: Prepared according to the silicon wafer as claimed in claim 15.

17. A photovoltaic module, characterized in that: The method comprises a plurality of solar cells according to claim 16 connected in series and / or in parallel.

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