Preparation method of photovoltaic cell and photovoltaic cell

Abstract

The invention discloses a preparation method of a photovoltaic cell and the photovoltaic cell, and the preparation method of the photovoltaic cell comprises the following steps: S1, placing a silicon rod in a guide rail of a cutting machine, wherein the guide rail can move in the vertical direction; s2, the movement speed of the cutting line is set to be 8 m / s to 38 m / s, the tension of the cutting line is set to be 3.4 N to 4 N, and the feeding speed of the guide rail is set to be 0.1 mm / min to 3.2 mm / min; s3, a cutting line is laid on a cutting main roller of the cutting machine; s4, the movement of the cutting line in the direction from the first line wheel to the second line wheel and then in the direction from the second line wheel to the first line wheel is set as a movement cycle, and the movement cycle runs in a reciprocating mode; and S5, starting a start button of the cutting machine, and cutting the silicon rod by the cutting line to obtain a plurality of silicon wafers. According to the preparation method of the photovoltaic cell, the step of moving the cutting line to the second line wheel before the silicon rod is cut is omitted, and the moving time of the cutting line is saved, so that the time for cutting the silicon rod is shortened, the production efficiency of a silicon wafer is improved, and the production efficiency of the photovoltaic cell is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of photovoltaic cells, and in particular to a preparation method of a photovoltaic cell and a photovoltaic cell. Background Art

[0002] In the related art, a silicon rod is usually cut into silicon wafers by a reverse cutting method. Before the silicon rod starts to be cut, the cutting wire on the wire pay-off reel is first run to the wire take-up reel, and then the wire cutting machine is started so that the new cutting wire first cuts the silicon rod, and then the old cutting wire cuts the silicon rod to cut the silicon rod into silicon wafers. However, in the above cutting process, the cutting wire needs to be run in reverse before cutting, resulting in a long production time and poor production efficiency of the photovoltaic cell. Summary of the Invention

[0003] The present invention aims to at least solve one of the technical problems existing in the prior art. For this reason, an object of the present invention is to provide a preparation method of a photovoltaic cell, which saves the running time of the cutting wire, thereby shortening the cutting time of the silicon rod, improving the production efficiency of the silicon wafers, and thus enhancing the production efficiency of the photovoltaic cell.

[0004] Another object of the present invention is to provide a photovoltaic cell prepared by using the above preparation method of the photovoltaic cell.

[0005] The preparation method of the photovoltaic cell according to the first aspect embodiment of the present invention includes the following steps:

[0006] S1. Place the silicon rod in the guide rail of the cutting machine, and the guide rail is movable in the vertical direction;

[0007] S2. Set the moving speed of the cutting wire to be 8 m / s to 38 m / s, the tension of the cutting wire to be 3.4 N to 4 N, and the feeding speed of the guide rail to be 0.1 mm / min to 3.2 mm / min;

[0008] S3. Lay the cutting wire on the cutting main roller of the cutting machine;

[0009] S4. Set the movement of the cutting wire first in the direction from the first wire wheel to the second wire wheel and then in the direction from the second wire wheel to the first wire wheel as a movement cycle, and the movement cycle runs reciprocally;

[0010] S5. Turn on the start button of the cutting machine, and make the silicon rod move vertically towards the cutting wire, and the cutting wire cuts the silicon rod to obtain a plurality of silicon wafers.

[0011] The manufacturing method of a photovoltaic cell according to an embodiment of the present invention moves the cutting wire in the direction from the first wire wheel to the second wire wheel during cutting. Compared with traditional reverse cutting, the step of running the cutting wire onto the second wire wheel before cutting the silicon rod is cancelled, saving the running time of the cutting wire, thus shortening the cutting time of the silicon rod, improving the production efficiency of the silicon wafer, and thereby enhancing the production efficiency of the photovoltaic cell.

[0012] According to some embodiments of the present invention, in step S2, the wire feeding amount of the first wire wheel is controlled to be greater than the wire returning amount of the second wire wheel.

[0013] According to some embodiments of the present invention, in step S2, the movement speed of the cutting wire includes the wire speed V1 at the knife-in stage, the wire speed V2 at the machining stage, the wire speed V3 at the end stage, and the acceleration a. Among them, V1, V2, V3, and a respectively satisfy: 8m / s ≤ V1 ≤ 15m / s, 35m / s ≤ V2 ≤ 38m / s, 25m / s ≤ V3 ≤ 30m / s, 5m / s 2 ≤ a ≤ 8m / s 2 。

[0014] According to some embodiments of the present invention, in step S2, the feeding speed of the guide rail includes the knife-in feeding speed V4, the main cutting feeding speed V5, and the retracting feeding speed V6. Among them, V4, V5, and V6 respectively satisfy: 1.2mm / min ≤ V4 ≤ 1.8mm / min, 2.2mm / min ≤ V5 ≤ 3.2mm / min, 0.1mm / min ≤ V6 ≤ 1.0mm / min.

[0015] According to some embodiments of the present invention, before step S2, there is also S2': adding a coolant to the liquid tank of the cutting machine, and the coolant is mixed with the liquid in the liquid tank to obtain a cutting fluid; among them, in step S5, the cutting fluid flows to the silicon rod and the cutting wire.

[0016] According to some embodiments of the present invention, in step S2, the flow rate of the cutting fluid is controlled to be 180L / min to 240L / min.

[0017] According to some embodiments of the present invention, the volume ratio of the coolant to the liquid in the liquid tank is (1.5L to 3.5L):(450L to 500L), and the temperature of the cutting fluid is 18°C to 22°C.

[0018] According to some embodiments of the present invention, after step S5, there is also:

[0019] S6. After cutting, turn off the cutting fluid, press the retracting button of the cutting machine, and move the silicon wafer away from the cutting wire in the vertical direction;

[0020] After the silicon wafer is completely separated from the cutting wire, the silicon wafer is removed by a blanking cart.

[0021] According to some embodiments of the present invention, the wire diameter of the cutting wire is D, where D satisfies: 28μm ≤ D ≤ 35μm.

[0022] The photovoltaic cell according to the embodiment of the second aspect of the present invention is prepared by using the preparation method of the photovoltaic cell according to the embodiment of the first aspect of the present invention above.

[0023] The additional aspects and advantages of the present invention will be given in part in the following description, will become apparent in part from the following description, or will be understood through the practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The above and / or additional aspects and advantages of the present invention will become apparent and easy to understand from the description of the embodiments in conjunction with the following drawings, where:

[0025] Figure 1 is a schematic diagram of a method for preparing a photovoltaic cell according to an embodiment of the present invention;

[0026] Figure 2 is a comparison diagram of the feed position, coolant concentration, and proportion of new cutting wire during reverse cutting;

[0027] Figure 3 is a comparison diagram of the feed position, coolant concentration, and proportion of new cutting wire during forward cutting;

[0028] Figure 4 is a partial schematic diagram of a cutting machine according to an embodiment of the present invention;

[0029] Figure 5 is Figure 4 a schematic diagram of the cutting machine and the silicon rod shown in

[0030] REFERENCE SIGNS:

[0031] 100: cutting machine; 1: main cutting roller; 2: cutting wire; 3: first wire wheel; 4: second wire wheel;

[0032] 200: silicon rod. DETAILED DESCRIPTION

[0033] The following refers to Figures 1-5 to describe a method for preparing a photovoltaic cell according to an embodiment of the first aspect of the present invention.

[0034] As Figures 1-5 shown, the method for preparing a photovoltaic cell according to an embodiment of the first aspect of the present invention includes the following steps:

[0035] S1. Place the silicon rod 200 in the guide rail of the cutting machine 100. The guide rail is movable in the vertical direction (for example, the up-and-down direction in Figure 5 ). When processing, select a silicon rod 200 suitable for the guide rail of the cutting machine 100. After a routine inspection of the silicon rod 200, clean the surface of the silicon rod 200 and place the silicon rod 200 in the guide rail of the cutting machine 100 so that the central axis of the silicon rod 200 is parallel to the central axis of the cutting main roller 1. Figure 5 After a routine inspection of the silicon rod 200, clean the surface of the silicon rod 200 and place the silicon rod 200 in the guide rail of the cutting machine 100 so that the central axis of the silicon rod 200 is parallel to the central axis of the cutting main roller 1.

[0036] S2. Set the moving speed of the cutting wire 2 to be 8 m / s - 38 m / s, the tension of the cutting wire 2 to be 3.4 N - 4 N, and the feeding speed of the guide rail to be 0.1 mm / min - 3.2 mm / min.

[0037] When the moving speed of the cutting wire 2 is less than 8 m / s, the moving speed of the cutting wire 2 is relatively small, which prolongs the cutting time of the silicon rod 200 and reduces the cutting efficiency of the silicon rod 200. When the moving speed of the cutting wire 2 is greater than 38 m / s, the moving speed of the cutting wire 2 on the cutting main roller 1 is relatively fast. In order to cut the silicon rod 200 into multiple silicon wafers, it is necessary to increase the length of the cutting wire 2 or increase the number of wire runs of the cutting wire 2, thereby increasing the cost of the cutting wire 2. At the same time, it is easy to cause uneven thickness at the cutting point of each silicon wafer, thereby increasing the TTV (Total Thickness Variation, the deviation between the thickest position and the thinnest position on the same silicon wafer) of the silicon wafer. Therefore, by setting the moving speed of the cutting wire 2 to be 8 m / s - 38 m / s, the moving speed of the cutting wire 2 is relatively moderate, which improves the cutting efficiency of the silicon rod 200 while reducing the cost of the cutting wire 2 and reducing the TTV of the silicon wafer.

[0038] When the tension of the cutting wire 2 is less than 3.4 N, the tension degree of the cutting wire 2 on the cutting main roller 1 is relatively low, resulting in a serious deviation of the wire bow during the cutting process, causing abnormal TTV of the silicon wafer, thereby affecting the cutting quality of the silicon wafer. When the tension of the cutting wire 2 is greater than 4 N, the tension degree of the cutting wire 2 on the cutting main roller 1 is relatively high, and the cutting wire 2 is prone to break during the cutting process of the silicon rod 200. Therefore, by setting the tension of the cutting wire 2 to be 3.4 N - 4 N, the tension of the cutting wire 2 is more reasonable, improving the cutting efficiency of the cutting wire 2 for the silicon rod 200, ensuring the quality of the silicon wafer while avoiding excessive tension of the cutting wire 2, thereby prolonging the service life of the cutting wire 2.

[0039] When the feeding speed of the guide rail is less than 0.1 mm / min, the moving speed of the silicon rod 200 in the vertical direction towards the cutting wire 2 is slow, thus prolonging the cutting time of the silicon rod 200 and reducing the cutting efficiency of the silicon rod 200; when the feeding speed of the guide rail is greater than 3.2 mm / min, the moving speed of the silicon rod 200 in the vertical direction towards the cutting wire 2 is fast, which easily causes the silicon rod 200 to press excessively against the cutting wire 2, and easily causes problems such as wire breakage of the cutting wire 2. Therefore, by setting the feeding speed of the guide rail at 0.1 mm / min to 3.2 mm / min, it is beneficial to control the moving speed of the silicon rod 200 in the vertical direction towards the cutting wire 2, ensuring the cutting efficiency of the silicon rod 200 while avoiding damage to the cutting wire 2.

[0040] S3. Lay the cutting wire 2 on the cutting main roller 1 of the cutting machine 100. Refer to Figure 4 and Figure 5 , the cutting machine 100 includes three cutting main rollers 1, the axes of the three cutting main rollers 1 are parallel to each other, and the cutting wire 2 is wound around the three cutting main rollers 1 and laid along the axis of the cutting main roller 1 to form a cutting wire network. Among them, the extension direction of the cutting wire 2 between any two of the three cutting main rollers 1 intersects with the axis of the cutting main roller 1 to cut the silicon rod 200 into multiple silicon wafers along its axis by using the cutting wire 2.

[0041] Among them, the cutting main roller 1 can be arranged below the guide rail in the vertical direction. During cutting, the guide rail is driven to drive the silicon rod 200 to move downward, so that the silicon rod 200 first contacts the cutting wire 2 on the cutting main roller 1, and then the silicon rod 200 further moves towards the direction of the cutting wire 2 to complete the complete cutting of the silicon rod 200.

[0042] S4. Set the movement of the cutting wire 2 from the first wire wheel 3 to the second wire wheel 4 first and then from the second wire wheel 4 to the first wire wheel 3 as a movement cycle, and the movement cycle runs reciprocally. That is to say, during cutting, the cutting wire 2 first runs from the first wire wheel 3 through the cutting main roller 1 to the second wire wheel 4 (forward cutting, at this time the first wire wheel 3 is the wire releasing wheel and the second wire wheel 4 is the wire taking-up wheel) to perform preliminary cutting on the silicon rod 200, and then the cutting wire 2 runs from the second wire wheel 4 through the cutting main roller 1 to the first wire wheel 3 (reverse cutting, at this time the first wire wheel 3 is the wire taking-up wheel and the second wire wheel 4 is the wire releasing wheel) to further cut the silicon rod 200. Repeat the above cutting process until the silicon wafers are cut. Compared with the traditional reverse cutting method (before cutting the silicon rod 200, running the cutting wire 2 from the first wire wheel 3 to the second wire wheel 4), it is beneficial to shorten the running time of the cutting wire 2, that is, to shorten the production time of cutting the silicon rod 200, thereby improving the production efficiency of the silicon wafers.

[0043] S5. Turn on the start button of the cutting machine 100, and move the silicon rod 200 vertically towards the cutting wire 2. The cutting wire 2 cuts the silicon rod 200 to obtain multiple silicon wafers. In the description of the present invention, "multiple" means two or more. The guide rail of the cutting machine 100 moves downward vertically, so that the silicon rod 200 gradually moves towards the cutting wire 2, and the cutting wire 2 is used to cut the silicon rod 200.

[0044] In addition, before cutting, check the cutting machine 100 according to the content of the inspection item checklist. After ensuring that there is no abnormality in each inspection item of the cutting machine 100, turn on the start button of the cutting machine 100 to ensure the smooth progress of cutting the silicon rod 200.

[0045] The preparation method of the photovoltaic cell is as follows: First, place the silicon rod 200 in the guide rail, and then lay the cutting wire 2 on the cutting main roller 1 to form a cutting wire network. Set various parameters of the cutting wire 2 (i.e., moving speed, tension), the feeding speed of the guide rail, and the cutting direction of the cutting wire 2 (when cutting, the cutting wire 2 first moves from the first wire wheel 3 to the second wire wheel 4, and then moves from the second wire wheel 4 to the first wire wheel 3), and then drive the guide rail to drive the silicon rod 200 to move towards the cutting wire 2, while the cutting wire 2 reciprocates in the above cutting direction, so as to cut the silicon rod 200 into multiple silicon wafers by using the cutting wire 2.

[0046] During the cutting process, the cutting wire 2 first moves from the first wire wheel 3 to the second wire wheel 4. The cutting wire 2 on the first wire wheel 3 cuts the silicon rod 200 and passes through the cutting main roller 1 to the second wire wheel 4 to complete the preliminary cutting of the silicon rod 200 in the vertical direction; when the movement of the cutting wire 2 from the first wire wheel 3 to the second wire wheel 4 ends, the cutting direction of the cutting wire 2 can be changed, that is, the cutting wire 2 moves from the second wire wheel 4 to the first wire wheel 3, so that the cutting wire 2 further cuts the silicon rod 200, and the cutting wire 2 reciprocates according to the above cutting process to completely cut the silicon rod 200 into multiple silicon wafers. Thereby, the utilization rate of the cutting wire 2 is improved, the length of the cutting wire 2 is reduced, and the efficiency of cutting the silicon rod 200 is improved.

[0047] For example, when the cutting equipment uses reverse cutting, a cutting equipment can cut 9.5 knives of silicon rods 200 in a day; while when the cutting equipment uses forward cutting, a cutting equipment can cut 11 knives of silicon rods 200 in a day. Thus, the efficiency of a cutting equipment using forward cutting is increased by 15.8% compared with that using reverse cutting, that is, the cutting efficiency is improved, and at the same time, the quality of the silicon wafers is also improved, thereby reducing the production cost of the silicon wafers.

[0048] The method for manufacturing a photovoltaic cell according to an embodiment of the present invention makes the cutting wire 2 move in the direction from the first wire wheel 3 to the second wire wheel 4 during cutting. Compared with traditional reverse cutting, the step of running the cutting wire 2 to the second wire wheel 4 before cutting the silicon rod 200 is cancelled, saving the running time of the cutting wire 2, thereby shortening the cutting time of the silicon rod 200, improving the production efficiency of silicon wafers, and thus enhancing the production efficiency of photovoltaic cells.

[0049] According to some embodiments of the present invention, referring to Figure 1 , in step S2, the wire feeding amount of the first wire wheel 3 is controlled to be greater than the wire returning amount of the second wire wheel 4. During the cutting process, the cutting wire 2 moves in a reciprocating manner of forward and reverse cutting. For example, the wire can first move from the first wire wheel 3 to the second wire wheel 4 for 500 m, and then return from the second wire wheel 4 to the first wire wheel 3 for 450 m. One wire feeding and one wire returning is a movement cycle, and 50 m of wire is fed to the second wire wheel 4 in one movement cycle. With such a setting, the usage times of the unit length of the cutting wire 2 are increased, thereby achieving full utilization of the cutting wire 2.

[0050] Specifically, when the cutting of the previous silicon rod 200 is completed, the cutting wire 2 on the cutting main roller 1 and the cutting wire 2 outside the first wire wheel 3 both participate in a relatively large number of cutting cycles, which can be called old cutting wires, and the cutting wire 2 near the center of the first wire wheel 3 participates in a relatively small number of cutting cycles, which can be called new cutting wires. When cutting a new silicon rod 200, the old cutting wires outside the cutting main roller 1 and the first wire wheel 3 first cut the silicon rod 200, and then the new cutting wire participates in the cutting. Thus, during the cutting process of the silicon rod 200, the old cutting wire is for knife entry and the new cutting wire is for knife withdrawal, improving the utilization rate of the cutting wire 2. At the same time, in the later stage of cutting, as the concentration of silicon powder becomes higher and the concentration of cutting fluid becomes lower, the new cutting wire, due to its better cutting force and better liquid carrying ability, is more conducive to improving the surface quality of the silicon wafer.

[0051] According to some embodiments of the present invention, referring to Figure 1 , in step S2, the movement speed of the cutting wire 2 includes the wire speed V1 in the knife entry stage, the wire speed V2 in the processing stage, the wire speed V3 in the end stage, and the acceleration a. Among them, V1, V2, V3, and a respectively satisfy: 8 m / s ≤ V1 ≤ 15 m / s, 35 m / s ≤ V2 ≤ 38 m / s, 25 m / s ≤ V3 ≤ 30 m / s, 5 m / s 2 ≤ a ≤ 8 m / s 2That is to say, the linear velocity in the tool entry stage and the linear velocity in the end stage are less than the linear velocity in the machining stage. Since the cutting depth of the cutting wire 2 in the silicon rod 200 is small in the tool entry stage and the end stage, and the cutting depth of the cutting wire 2 in the silicon rod 200 is large in the machining stage, the movement speed and cutting depth of the cutting wire 2 are controlled according to the operating stage of the cutting wire 2. While ensuring the normal wire bow, the cutting wire 2 is fully utilized, and the cutting quality can be guaranteed, thereby ensuring the quality of the silicon wafers.

[0052] When V1 < 8 m / s, the linear velocity of the cutting wire 2 in the tool entry stage is small, and the cutting effect of the cutting wire 2 on the silicon rod 200 is poor, reducing the cutting efficiency; when V1 > 15 m / s, the linear velocity of the cutting wire 2 in the tool entry stage is large, which is likely to cause uneven thickness of each silicon wafer at the cutting point, increasing the TTV of the silicon wafers. Therefore, by setting the linear velocity of the cutting wire 2 in the tool entry stage to 8 m / s ≤ V1 ≤ 15 m / s, the linear velocity of the cutting wire 2 in the tool entry stage is reasonable, the cutting ability of the cutting wire 2 on the silicon rod 200 is strong, and at the same time, it is convenient for the cutting wire 2 to cut into the silicon rod 200, ensuring the consistency of the thickness of each silicon wafer at the cutting point, reducing the TTV of the silicon wafers, and improving the quality of the silicon wafers.

[0053] When V2 < 35 m / s, the linear velocity of the cutting wire 2 in the machining stage is small, and the cutting force of the cutting wire 2 on the silicon rod 200 is poor, reducing the cutting efficiency; when V2 > 38 m / s, the linear velocity of the cutting wire 2 in the machining stage is large, it is difficult to control the TTV of the silicon wafers, and the cutting quality is low, reducing the quality of the silicon wafers. Therefore, by setting the linear velocity of the cutting wire 2 in the machining stage to 35 m / s ≤ V2 ≤ 38 m / s, the linear velocity of the cutting wire 2 in the machining stage is reasonable, the cutting ability of the cutting wire 2 on the silicon rod 200 is strong, and at the same time, the TTV of the silicon wafers can be reduced, thereby improving the cutting quality and the quality of the silicon wafers.

[0054] When V3 < 25 m / s, the linear velocity of the cutting wire 2 in the end stage is small, and the cutting force of the cutting wire 2 on the silicon rod 200 is poor, and it is difficult to control the cutting wire 2 to completely penetrate the silicon rod 200 to cut the silicon rod 200 into multiple independent silicon wafers; when V3 > 30 m / s, the linear velocity of the cutting wire 2 in the end stage is large, it is difficult to control the TTV at the cut-out point of the silicon wafers, and the cutting quality is low, thereby reducing the quality of the silicon wafers. Therefore, by setting the linear velocity of the cutting wire 2 in the end stage to 25 m / s ≤ V3 ≤ 30 m / s, the linear velocity of the cutting wire 2 in the end stage is reasonable, the cutting ability of the cutting wire 2 on the silicon rod 200 is strong, and at the same time, the TTV of the silicon wafers at the cut-out point can be reduced, thereby improving the cutting quality and the quality of the silicon wafers.

[0055] When a < 5 m / s 2When the acceleration of the cutting line 2 is small, the number of uses of some of the cutting line 2 is large, while the number of uses of the remaining part of the cutting line 2 is small, reducing the wear uniformity of the cutting line 2 during the cutting process, easily reducing the quality of the silicon wafer surface, and the part of the cutting line 2 with a large number of uses is prone to breakage; when a > 8 m / s 2 When the number of cuts of the cutting line 2 per unit length on the silicon rod 200 is small, to meet the cutting requirements of the silicon rod 200, multiple turns in the cutting direction of the cutting line 2 need to be increased, which will reduce the cutting efficiency. Therefore, by setting the acceleration of the cutting line 2 to 5 m / s 2 ≤a≤8 m / s 2 is beneficial to improving the utilization rate of the cutting line 2 and the cutting efficiency of the silicon rod 200.

[0056] For example, the linear velocity of the cutting line 2 at the tool entry stage is 8 m / s, the linear velocity of the cutting line 2 at the processing stage is 38 m / s, the linear velocity of the cutting line 2 at the end stage is 30 m / s, and the acceleration of the cutting line 2 is 5.7 m / s 2 .

[0057] According to some specific embodiments of the present invention, referring to Figure 1 , in step S2, the feed speed of the guide rail includes the tool entry feed speed V4, the main cutting feed speed V5, and the tool withdrawal feed speed V6, where V4, V5, and V6 respectively satisfy: 1.2 mm / min ≤ V4 ≤ 1.8 mm / min, 2.2 mm / min ≤ V5 ≤ 3.2 mm / min, 0.1 mm / min ≤ V6 ≤ 1.0 mm / min. A smaller tool entry feed speed is conducive to the cutting line 2 cutting into the silicon rod 200, avoiding uneven thickness at the cutting point of each silicon wafer; a larger main cutting feed speed makes the main cutting feed speed suitable for the cutting requirements of the cutting line 2 on the silicon rod 200, realizing rapid cutting of the silicon rod 200 and improving the cutting efficiency; a smaller tool withdrawal feed speed reduces the cutting speed of the cutting line 2 on the silicon rod 200, thereby avoiding uneven thickness at the cut-out point of each silicon wafer, and gradually stopping the operation of the guide rail at the same time, avoiding energy waste of the cutting machine 100.

[0058] When V4 < 1.2 mm / min, the moving speed of the silicon rod 200 towards the cutting line 2 is small, reducing the cutting efficiency of the silicon rod 200; when V4 > 1.8 mm / min, the moving speed of the silicon rod 200 towards the cutting line 2 is fast, easily causing uneven thickness at the cutting point of each silicon wafer, thereby increasing the TTV of the silicon wafer. Therefore, by setting the tool entry feed speed of the guide rail to 1.2 mm / min ≤ V4 ≤ 1.8 mm / min, it is beneficial to improve the cutting efficiency of the cutting line 2 on the silicon rod 200, while improving the thickness uniformity at the cutting point of each silicon wafer, thereby reducing the TTV of the silicon wafer and improving the quality of the silicon wafer.

[0059] When V5 < 2.2 mm / min, the moving speed of the silicon rod 200 towards the cutting wire 2 cannot meet the cutting depth requirement of the cutting wire 2 for the silicon rod 200, making it easy for the cutting wire 2 to jump out of the silicon rod 200, thus reducing the cutting efficiency of the silicon rod 200; when V5 > 3.2 mm / min, the cutting depth of the cutting wire 2 in the vertical direction for the silicon rod 200 is less than the distance that the silicon rod 200 moves towards the cutting wire 2, causing the silicon rod 200 to press against the cutting wire 2 excessively, easily damaging the cutting wire 2 and reducing the service life of the cutting wire 2. Therefore, by setting the main cutting feed speed of the guide rail to 2.2 mm / min ≤ V5 ≤ 3.2 mm / min, the design of the cutting depth of the cutting wire 2 in the vertical direction for the silicon rod 200 and the distance that the silicon rod 200 moves towards the cutting wire 2 is made more reasonable, thereby improving the cutting efficiency of the silicon rod 200 while extending the service life of the cutting wire 2.

[0060] When V6 < 0.1 mm / min, near the end of cutting, the moving speed of the silicon rod 200 towards the cutting wire 2 is small, prolonging the time to completely cut the silicon rod 200 into silicon wafers, thus reducing the cutting efficiency of the silicon rod 200; when V6 > 1.0 mm / min, near the end of cutting, the moving speed of the silicon rod 200 towards the cutting wire 2 is large, making it difficult to control the TTV of the silicon wafer at the cutting-out point, resulting in low cutting quality and thus low silicon wafer quality. Therefore, by setting the retracting feed speed of the guide rail to 0.1 mm / min ≤ V6 ≤ 1.0 mm / min, it is beneficial to improve the cutting efficiency of the silicon rod 200, improve the cutting quality of the silicon rod 200, and thus improve the quality of the silicon wafers.

[0061] For example, the feed speed of the guide rail for the tool entry can be 1.8 mm / min, the main cutting feed speed of the guide rail can be 2.0 mm / min, 2.1 mm / min, 2.2 mm / min, 2.3 mm / min or 2.4 mm / min, and the retracting feed speed of the guide rail can be 0.3 mm / min, 0.4 mm / min or 0.5 mm / min.

[0062] In addition, referring to Figure 1 , before step S2, it further includes:

[0063] S2'. Add coolant to the liquid tank of the cutting machine 100, and the coolant is mixed with the liquid in the liquid tank to obtain the cutting fluid. Among them, in step S5, the cutting fluid flows towards the silicon rod 200 and the cutting wire 2. The cutting fluid has functions such as lubrication and wetting. The cutting fluid flowing towards the silicon rod 200 and the cutting wire 2 increases the cutting smoothness of the cutting wire 2 for the silicon rod 200, thus improving the cutting efficiency of the cutting wire 2 for the silicon rod 200. Using the liquid in the liquid tank to mix the coolant to form the cutting fluid simplifies the mixing difficulty of the cutting fluid, further reduces the preparation difficulty of the photovoltaic cell, and improves the preparation efficiency of the photovoltaic cell.

[0064] Reference Figure 2 and Figure 3 In the initial stage of cutting the silicon rod 200, when the concentration of the coolant in the cutting fluid is relatively high, the old cutting wire participates in the cutting. As the concentration of the coolant in the cutting fluid decreases, the new cutting wire participates in the cutting. The new cutting wire has better cutting force and better liquid-carrying ability, compensating for the problem of insufficient cutting force caused by the decrease in the concentration of the coolant in the cutting fluid, and improving the efficiency of the cutting wire 2 in cutting the silicon rod 200.

[0065] Optionally, after laying the cutting wire mesh, 2L to 3L of coolant can be added.

[0066] Furthermore, in step S2, the flow rate of the cutting fluid is controlled to be 180L / min to 240L / min. When the flow rate of the cutting fluid is less than 180L / min, the cutting fluid cannot meet the lubrication and wetting requirements of the cutting wire 2; when the flow rate of the cutting fluid is greater than 240L / min, a large amount of foam is easily generated in the cutting fluid, thus affecting the cutting quality of the silicon wafer. Therefore, by setting the flow rate of the cutting fluid to 180L / min to 240L / min, the flow rate of the cutting fluid is made more reasonable, meeting the lubrication and wetting requirements of the cutting wire 2 while reducing the generation of foam, thereby improving the cutting efficiency of the cutting wire 2 for the silicon rod 200 and enhancing the quality of the silicon wafer.

[0067] For example, the flow rate of the cutting fluid is 220L / min.

[0068] In addition, the volume ratio of the coolant to the liquid in the liquid tank is (1.5L to 3.5L):(450L to 500L). The volume ratio of the coolant to the liquid in the liquid tank is relatively reasonable, so that the formed cutting fluid meets the lubrication and wetting requirements of the cutting wire 2 while making full use of the liquid in the liquid tank, reducing the amount of coolant used, and lowering the production cost.

[0069] The temperature of the cutting fluid is 18°C to 22°C. When the temperature of the cutting fluid is less than 18°C, the temperature of the cutting fluid is relatively low, and the surfactant in the cutting fluid cannot fully play its role, so the lubrication and wetting effect of the cutting fluid on the cutting wire 2 is relatively poor; when the temperature of the cutting fluid is greater than 22°C, the temperature of the cutting fluid is relatively high, making it easier for the cutting fluid to generate bubbles, affecting the cutting quality. Therefore, by setting the temperature of the cutting fluid to 18°C to 22°C, it is beneficial for components such as the surfactant in the cutting fluid to play their roles, enhancing the lubrication and wetting effect of the cutting fluid on the cutting wire 2 while reducing the number of bubbles in the lubricating fluid, thereby improving the cutting efficiency of the cutting wire 2 for the silicon rod 200 and enhancing the quality of the silicon wafer.

[0070] For example, the volume ratio of the coolant to the liquid in the liquid tank is 2.5L:500L, and the temperature of the cutting fluid is 20°C.

[0071] According to some embodiments of the present invention, such asFigure 1 As shown, after step S5, it further includes:

[0072] S6. After the cutting is completed, turn off the cutting fluid, and press the retraction button of the cutting machine 100 to move the silicon wafer away from the cutting line 2 in the vertical direction. With such a setting, the cutting fluid can wet and lubricate all the cutting lines 2 as much as possible to complete the cutting of the silicon rod 200 by the cutting lines 2. After the cutting is completed, the silicon wafer is moved out of the cutting line network in the vertical direction to prevent the silicon wafer from contacting the cutting line 2 and reducing the surface quality of the silicon wafer.

[0073] S7. After the silicon wafer is completely separated from the cutting line 2, use a blanking cart to remove the silicon wafer. When the silicon wafer is separated from the cutting line 2, the silicon wafer can be moved out in any direction intersecting with the vertical direction to remove the silicon wafer from the cutting machine 100 for the next operation.

[0074] According to some embodiments of the present invention, the wire diameter of the cutting line 2 is D, where D satisfies: 28μm ≤ D ≤ 35μm. When D < 28μm, the wire diameter of the cutting line 2 is relatively small, and the effective cutting area of the cutting line 2 on the silicon rod 200 is relatively small, resulting in a relatively large pressure on the cutting line 2, so that the cutting line 2 is easily damaged during the cutting process, thereby reducing the service life of the cutting line 2; when D > 35μm, the wire diameter of the cutting line 2 is relatively large, and the effective cutting area of the cutting line 2 on the silicon rod 200 is relatively large, so that the pressure on the cutting line 2 is relatively small, reducing the cutting force of the cutting line 2 on the silicon rod 200, and thus reducing the cutting efficiency of the cutting line 2 on the silicon rod 200. Therefore, by setting the wire diameter of the cutting line 2 to 28μm ≤ D ≤ 35μm, the wire diameter design of the cutting line 2 is more reasonable, that is, the effective cutting area design of the cutting line 2 on the silicon rod 200 is more reasonable, which is beneficial to improving the cutting efficiency of the cutting line 2 on the silicon rod 200 while extending the service life of the cutting line 2.

[0075] The other components and operations of the cutting machine 100 according to the embodiments of the present invention are known to those of ordinary skill in the art and will not be described in detail here.

[0076] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "center", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "bottom", "inner", "outer", "axial", "radial", "circumferential", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention.

[0077] In the description of the present application, it should be noted that unless otherwise clearly defined and limited, the terms "installed", "connected", and "coupled" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two components. 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 situations.

[0078] In the description of this specification, the descriptions with reference to the terms "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples", etc. mean that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiment or example.

[0079] Although the embodiments of the present invention have been shown and described, those of ordinary skill in the art can understand that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and purposes of the present invention. The scope of the present invention is defined by the claims and their equivalents.

Claims

1. A method for preparing a photovoltaic cell, characterized in that, It includes the following steps: S1. Place the silicon rod in the guide rail of the cutting machine, and the guide rail is movable in the vertical direction; S2. Set the moving speed of the cutting wire to be 8 m / s to 38 m / s, the tension of the cutting wire to be 3.4 N to 4 N, and the feeding speed of the guide rail to be 0.1 mm / min to 3.2 mm / min; S3. Lay the cutting wire on the main cutting roller of the cutting machine; S4. Set the movement of the cutting wire from the first wire wheel to the second wire wheel and then from the second wire wheel to the first wire wheel as one movement cycle, and the movement cycle runs reciprocally; S5. Turn on the start button of the cutting machine to make the silicon rod move vertically towards the cutting wire, and the cutting wire cuts the silicon rod to obtain a plurality of silicon wafers.

2. The manufacturing method of the photovoltaic cell according to claim 1, wherein, In step S2, control the wire feeding amount of the first wire wheel to be greater than the wire returning amount of the second wire wheel.

3. The preparation method of the photovoltaic cell according to claim 1, wherein, In step S2, the moving speed of the cutting line includes the linear speed V1 in the tool entry stage, the linear speed V2 in the machining stage, the linear speed V3 in the end stage, and the acceleration a. Among them, the V1, V2, V3, and a respectively satisfy: 8 m / s ≤ V1 ≤ 15 m / s, 35 m / s ≤ V2 ≤ 38 m / s, 25 m / s ≤ V3 ≤ 30 m / s, 5 m / s 2 ≤ a ≤ 8 m / s 2 .

4. The method for preparing a photovoltaic cell according to claim 1, wherein, In step S2, the feeding speed of the guide rail includes the feed-in feeding speed V4, the main cutting feeding speed V5, and the feed-out feeding speed V6. Among them, V4, V5, and V6 respectively satisfy: 1.2 mm / min ≤ V4 ≤ 1.8 mm / min, 2.2 mm / min ≤ V5 ≤ 3.2 mm / min, 0.1 mm / min ≤ V6 ≤ 1.0 mm / min.

5. The method for preparing a photovoltaic cell according to claim 1, characterized in that, Before step S2, it further includes: S2'. Add coolant to the liquid tank of the cutting machine, and the coolant is mixed with the liquid in the liquid tank to obtain cutting fluid; Among them, in step S5, the cutting fluid flows towards the silicon rod and the cutting wire.

6. The manufacturing method of a photovoltaic cell according to claim 5, wherein, In step S2, control the flow rate of the cutting fluid to be 180 L / min to 240 L / min.

7. The manufacturing method of the photovoltaic cell according to claim 5, characterized in that, The volume ratio of the coolant to the liquid in the liquid tank is (1.5 L to 3.5 L):(450 L to 500 L), and the temperature of the cutting fluid is 18 °C to 22 °C.

8. The manufacturing method of a photovoltaic cell according to claim 5, characterized in that, After step S5, it further includes: S6. After cutting, turn off the cutting fluid, turn on the retraction button of the cutting machine, and make the silicon wafers move vertically away from the cutting wire; S7. After the silicon wafers are completely separated from the cutting wire, use a blanking cart to remove the silicon wafers.

9. The method for preparing a photovoltaic cell according to any one of claims 1-8, characterized in that, The wire diameter of the cutting wire is D, where D satisfies: 28 μm ≤ D ≤ 35 μm.

10. A photovoltaic cell, characterized in that, Prepared by using the preparation method of the photovoltaic cell according to any one of claims 1-9.

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