A sliced battery and a method and apparatus for manufacturing the same

Abstract

The present application belongs to the field of crystalline silicon solar cells, and relates to a sliced cell and a preparation method and equipment thereof. The preparation method comprises the following steps: providing a solar cell; cutting the solar cell to obtain a sliced cell, the sliced cell having a front surface and a back surface and a cutting surface; performing passivation treatment on the cutting surface to form a passivation layer; stacking the sliced cells in a manner that the passivation layers face the same direction to form a sliced cell stack, the first main surface of the sliced cell stack having a first region at one end close to the passivation layer, and the second main surface of the sliced cell stack having a second region at one end close to the passivation layer; performing first laser annealing treatment on the first region; turning over the sliced cell stack; and performing second laser annealing treatment on the second region. Through the two separate laser annealing treatments on the first region and the second region, the hydroxyl and defects generated during the oxidation film plating are eliminated, the annealing uniformity is improved, the photovoltaic module yield is improved, and the overall structure of the solar cell is not damaged.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of crystalline silicon solar cell, in particular to a cut cell and a preparation method and equipment thereof. BACKGROUND

[0002] Due to the advantages of reducing current, reducing resistance loss, improving photovoltaic module voltage and output power, a complete cell is usually divided into multiple half cells when manufacturing edge passivation solar cell, and then the half cells are manufactured into modules in a series and parallel manner. The half cell technology is to cut a standard specification cell (156mmx156mm) into two pieces (156x78mm) by laser, and then connect the cut pieces. The cell pieces of the entire photovoltaic module are divided into two groups, each group containing 60 cut cells connected in series. A complete 120-piece module is formed, so that the current passing through each main grid can be reduced to 1 / 2 of the original, the internal loss can be reduced to 1 / 4 of the whole cell, and the power of the photovoltaic module can be improved.

[0003] In industrial applications, there are various ways to cut cell pieces, including laser cutting, waterless cutting, etc. However, no matter which method is used, due to the interaction between the cutting tool and the cutting liquid, micro-damage and defects are generated on the surface of the silicon wafer. These damages and defects increase the surface recombination rate of the cut silicon wafer, because they provide more recombination centers, making it easier for minority carriers to recombine at these locations, thereby reducing the minority carrier lifetime, which has a greater adverse effect on the electrical performance of the solar cell. Among them, the laser cutting process often brings a large number of dangling bonds and impurities. Dangling bonds refer to unpaired chemical bonds on the surface of a semiconductor material due to the destruction of the periodic structure of the crystal lattice. These dangling bonds not only increase the defect state density of the crystalline silicon surface, but also affect the electrochemical performance of the cell piece, specifically the passivation performance, which has a serious impact on the minority carrier lifetime of the cell piece. For example, when cutting a TOPCon solar cell piece using a laser scribing method, the cross section is usually an unpassivated silicon wafer cross section, which increases the edge recombination of the cutting surface, resulting in a significant reduction in cell conversion efficiency.

[0004] In recent years, the method of improving cell efficiency and photovoltaic module power through edge passivation technology has been increasingly popular in the development of new solar cell technology. Through in-depth research, it is found that the edge passivation coating treatment method of the cutting surface of the cell piece can effectively improve the characteristics of the cutting surface and reduce the number of recombination centers. Passivation coating refers to forming a passivation film on the surface of the cutting surface of the cell piece through deposition, providing field passivation effect, thereby reducing minority carrier recombination and reducing reflectivity.

[0005] Therefore, in order to improve the battery efficiency, passivation coating is a good choice for the cutting surface, but in the process of edge passivation coating of aluminum oxide film with water vapor as oxygen source, hydroxyl and some defects such as melting, scratches or micro-cracks will be generated. Therefore, an annealing step is generally added after passivation to activate the hydrogen passivation inside the battery and eliminate the defects generated by edge passivation. Unlike ordinary annealing, the principle of laser annealing is to use a laser beam to irradiate the surface of the semiconductor, generating extremely high temperature in the irradiation area to repair the damage of the crystal and eliminate dislocations.

[0006] However, the current laser annealing method has the problem of uneven annealing, and the effect of eliminating passivation defects is also limited. SUMMARY

[0007] Therefore, a kind of sliced battery and its preparation method and equipment are provided, which eliminates the hydroxyl and defects generated by edge passivation when coating the oxide film layer on the cutting surface by respectively performing first laser annealing treatment and second laser treatment on the first region and the second region of the sliced battery, improves the uniformity of annealing, improves the yield of photovoltaic modules, and does not damage the overall structure of the battery.

[0008] In one aspect, a sliced battery preparation method is provided, comprising the following steps:

[0009] providing a solar cell;

[0010] cutting the solar cell to obtain a plurality of sliced batteries, the sliced battery having opposite front and back surfaces, and at least one cutting surface connecting the front and back surfaces;

[0011] passivating the cutting surface of the sliced battery to form a passivation layer on the cutting surface of the sliced battery;

[0012] stacking a plurality of sliced batteries in a way that the passivation layer of the sliced battery faces the same direction to form a sliced battery stack, the first main surface of the sliced battery stack near one end of the passivation layer has a first region, and the second main surface of the sliced battery stack near one end of the passivation layer has a second region;

[0013] laser annealing treatment of the sliced battery stack, the laser annealing treatment comprising:

[0014] first laser annealing treatment: performing first laser annealing treatment on the first region of the sliced battery stack;

[0015] turning over the sliced battery stack;

[0016] second laser annealing treatment: performing second laser annealing treatment on the second region of the sliced battery stack.

[0017] In one embodiment, the first region and the second region are 1-2 mm away from the cutting surface.

[0018] In one embodiment, the laser power of the first laser annealing process and the second laser annealing process is the same.

[0019] Preferably, the laser power of the first laser annealing process and the second laser annealing process is 55-68 W, and the heating temperature of the first region by the first laser annealing process and the heating temperature of the second region by the second laser annealing process are both 275-280℃.

[0020] Preferably, the laser power of the second laser annealing is lower than that of the first laser annealing.

[0021] Preferably, the laser power of the first laser annealing process is 55-68 W, and the heating temperature of the first region by the first laser annealing process is 275-280℃; the laser power of the second laser annealing process is 30-50 W, and the heating temperature of the second region by the second laser annealing process is 250-255℃.

[0022] In one embodiment, the thickness d of the sliced battery is 120-123 um, and the number of stacked sliced batteries 3 in a stack is 30-50.

[0023] In one embodiment, the method further comprises a performance detection step of the sliced battery after the second laser annealing process, and when the performance detection finds that the sliced battery after the second laser annealing process is unqualified, the unqualified sliced battery repeats the first laser annealing process and the second laser annealing process until the sliced battery is qualified.

[0024] Preferably, the performance detection includes detecting at least one of the appearance, EL, open pressure, current, fill factor, photoelectric conversion efficiency, and yield rate of the sliced battery.

[0025] In one embodiment, the sliced battery is cooled before performance detection, and the cooling time is 3.5-5 min, and the final temperature of the cooling process is 24-26℃.

[0026] In one embodiment, the sliced battery has one cutting surface or two cutting surfaces.

[0027] In one embodiment, the laser of the first laser annealing process and the second laser annealing process forms an angle of 30-60 degrees with the horizontal line.

[0028] In one embodiment, the solar cell is a TOPCon cell, a PERC cell or a HIT cell.

[0029] In another aspect, a sliced cell is provided, which is prepared by any one of the above-mentioned preparation methods.

[0030] In another aspect, a laser annealing device is provided for the laser annealing step in any one of the above-mentioned sliced cell preparation methods, the device having a cavity, the device comprising:

[0031] A conveying device is arranged in the cavity and used to convey the sliced cell stack;

[0032] A laser is arranged in the cavity above the conveying device, and the laser is arranged obliquely at an angle of 30-60 degrees with the horizontal line, so that the emitted laser is irradiated on the first area and / or the second area at an angle of 30-60 degrees.

[0033] The present application has at least one of the following beneficial effects:

[0034] The sliced cell preparation method provided by the embodiments of the present application can ensure the annealing uniformity of the cutting surface of the sliced cell, completely eliminate the defects caused by the passivation of the cutting surface of the sliced cell, and will not damage other film layers of the sliced cell, thereby protecting the overall structure of the sliced cell.

[0035] The present application cuts the solar cell to obtain a slice cell, performs passivation treatment on the cutting surface of the slice cell to form a passivation layer, reduces the adverse effects of a large number of dangling bonds and impurities on the slice cell, and then respectively performs first laser annealing treatment and second laser treatment on the first region and the second region of the slice cell. Through the first laser annealing treatment, the microstructure of the cutting surface is preliminarily improved, the thermal damage and micro-defects generated in the laser cutting process are reduced, the surface roughness is reduced, the residual stress generated during cutting is eliminated, and the crystal grains are refined, so that the microstructure of the cutting surface is improved and the influence of thermal damage on photoelectric performance is reduced. Further, through the second laser annealing treatment, the microstructure of the cutting surface is further improved on the basis of the first laser annealing treatment, and the cutting surface regions that are not treated by the first laser annealing treatment are supplemented, so as to ensure the uniformity and integrity of the annealing effect. The hydroxyl groups and defects generated after passivation of the oxidation edge of the cutting surface are eliminated, the annealing uniformity is improved, and the yield of photovoltaic modules is improved. Direct laser irradiation of the cutting surface is avoided, which can cause excessive energy and damage other film layers of the slice cell, and the overall structure of the cell is not damaged. BRIEF DESCRIPTION OF DRAWINGS

[0036] Figure 1 The annealing method flowchart provided by an embodiment of the present application;

[0037] Figure 2 The structure schematic diagram of the slice cell provided by an embodiment of the present application, wherein, the reference numerals 2 and 7 mark two opposite surfaces;

[0038] Figure 3 The process schematic diagram when performing laser annealing treatment provided by an embodiment of the present application;

[0039] Figure 4 The SEM diagram of the half cell after annealing treatment by the annealing method provided by an embodiment of the present application;

[0040] Figure 5 The SEM diagram of the half cell after annealing treatment by the annealing method of the comparative example.

[0041] REFERENCE NUMERALS

[0042] 1, cavity; 2, first region; 3, slice cell; 31, cutting surface; 32, oxidation film layer; 4, conveying device; 5, laser; 6, exhaust system; 7, second region. DETAILED DESCRIPTION

[0043] In order to make the purpose, technical scheme and advantages of the present application clearer, the present application is further described in detail below in combination with the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and do not limit the present application.

[0044] It should be noted that the diagrams provided in the present embodiment only schematically illustrate the basic concept of the present application, and only the components related to the present application are shown in the diagrams, rather than being drawn according to the number, shape and size of the components in actual implementation. The actual implementation of each component can be a random change, and the component layout can be more complex.

[0045] The structure, proportion, size, etc. shown in the drawings of the present specification are only used to cooperate with the content disclosed in the specification, so that those skilled in the art can understand and read, and are not used to limit the conditions that the present application can be implemented. Therefore, any modification of the structure, change of the proportion relationship or adjustment of the size, without affecting the effect and purpose that the present application can produce, should still fall within the scope of the technical content disclosed by the present application.

[0046] The orientations or positional relationships indicated by terms such as "upper", "lower", "left", "right", "intermediate", "longitudinal", "lateral", "horizontal", "inner", "outer", "radial", "circumferential", etc. in the present specification are based on the orientations or positional relationships shown in the drawings, and are only used to simplify the description, and cannot be understood as indicating or implying that the device or element must have a particular orientation, be constructed and operated in a particular orientation. Therefore, it cannot be understood as a limitation on the present application. In addition, the terms "first", "second", etc. are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance.

[0047] The current laser annealing method for the cutting surface of the battery mainly includes: a laser beam directly irradiates the cutting surface of the battery for annealing, and the laser beam covers the entire cutting surface. When the applicant anneals the cutting surface of the half battery according to the existing annealing method, it is found that the annealing is not uniform, and the effect of eliminating the edge passivation defects is also limited. From the perspective of passivation microstructure, the structure of the half battery after annealing is severely damaged, the tunnel oxide layer and the poly silicon layer of the half battery are completely destroyed, and the film layer structure of the half battery is also damaged to different degrees.

[0048] In order to eliminate the hydroxyl and defects generated after the edge passivation of the half battery while reducing the damage to the overall structure of the half battery, thereby improving the yield of photovoltaic modules and achieving the purpose of reducing cost and increasing efficiency. The applicant tries to analyze the reasons for the above problems existing in the existing annealing method.

[0049] The research finds that when laser annealing is performed on the half-cell, in order to improve the annealing efficiency, a plurality of half-cells are stacked into a neat stack, the cutting surfaces of the half-cells in the stack are oriented to the same side, the cutting surfaces are passivated to form passivation layers, and then the top surface of the stack of half-cells is irradiated by laser to perform annealing. However, due to the thickness of the stack of half-cells, when laser annealing is performed, the energy distribution of the laser is uneven after the laser penetrates the upper half-cells, thereby affecting the annealing effect of the middle and lower half-cells. If the annealing effect of the middle and lower half-cells is improved by increasing the laser power or prolonging the laser irradiation time, the upper half-cells are overheated, and appropriate laser parameters cannot be found. Therefore, the current annealing method of irradiating the top surface of the stack of half-cells by one laser beam cannot uniformly anneal different regions of the half-cells, and the structure of some half-cells is severely damaged, the tunneling oxide layer and the poly silicon layer of the half-cells are damaged, the film structure is damaged to different degrees, and the effect of eliminating the edge passivation defects is also limited.

[0050] Therefore, the laser annealing is performed on the half-cells in different regions, and the results show that after the laser annealing is performed on the half-cells in different regions, the hydroxyl and defects generated during the edge passivation of the oxide film can be better eliminated, thereby improving the yield of photovoltaic modules and achieving the purpose of reducing cost and increasing efficiency, and the overall structure of the half-cells is not damaged.

[0051] The half-cell in the present application refers to two identical cells formed by cutting a standard cell along a direction perpendicular to the main grid line of the cell, and is also called a two-split cell. Each half-cell has one cutting surface.

[0052] The three-split cell in the present application refers to three identical cells formed by cutting a standard cell along a direction perpendicular to the main grid line of the cell, and each three-split cell has two cutting surfaces. Similarly, when four, five or more identical cells are formed by cutting a standard cell along a direction perpendicular to the main grid line of the cell, the cells are called four-split cells, five-split cells, etc., and all have two cutting surfaces.

[0053] The first main surface of the slice cell stack in the present application refers to the surface on one side of the slice cell stack along the stacking direction of the slice cells, that is, one of the two largest surfaces of the slice cell stack, which is located on one of the outermost slice cells of the slice cell stack.

[0054] The second main surface of the slice cell stack in the present application refers to the surface on the other side of the slice cell stack along the stacking direction of the slice cells, that is, the other of the two largest surfaces of the slice cell stack, which is located on the other of the outermost slice cells of the slice cell stack.

[0055] Embodiments

[0056] A method for preparing a sliced battery, referring to Figure 1 , comprising:

[0057] providing a solar cell;

[0058] cutting the solar cell to obtain a plurality of sliced batteries 3, the sliced batteries 3 having opposite front and back surfaces, and at least one cutting surface 31 connecting the front and back surfaces;

[0059] passivating the cutting surface 31 of the sliced battery 3 to form a passivation layer on the cutting surface 31 of the sliced battery 3;

[0060] stacking a plurality of sliced batteries 3 into a sliced battery stack with the passivation layers of the sliced batteries 3 facing the same direction, the first main surface of the sliced battery stack having a first region 2 at one end close to the passivation layer, and the second main surface of the sliced battery stack having a second region 7 at one end close to the passivation layer;

[0061] performing laser annealing treatment on the sliced battery stack, the laser annealing treatment comprising:

[0062] first laser annealing treatment: performing first laser annealing treatment on the first region 2 of the sliced battery stack;

[0063] turning over the sliced battery stack;

[0064] second laser annealing treatment: performing second laser annealing treatment on the second region 7 of the sliced battery stack.

[0065] The method for preparing a sliced battery provided by the embodiments of the present application, based on the mutual compensation of the first laser annealing treatment on the first main surface of the sliced battery stack and the second laser annealing treatment on the second main surface, can not only ensure the uniform annealing of the cutting surface 31 of the sliced battery 3, but also completely eliminate the defects caused by the passivation of the cutting surface 31 of the sliced battery 3, and will not damage other film layers of the sliced battery 3, protecting the overall structure of the sliced battery 3.

[0066] Specifically, the present application cuts the solar cell to obtain a cut cell 3, performs passivation treatment on the cutting surface 31 of the cut cell 3 to form a passivation layer, reduces the adverse effects of a large number of dangling bonds and impurities brought by the cutting surface 31 on the cut cell 3, and then respectively performs first laser annealing treatment and second laser treatment on the first region 2 and the second region 7 of the cut cell 3. Through the first laser annealing treatment, the microstructure of the cutting surface 31 is preliminarily improved, the thermal damage and micro defects generated in the laser cutting process are reduced, the surface roughness is reduced, the residual stress generated during cutting is eliminated, and the grain is refined, so that the microstructure of the cutting surface 31 is improved, and the influence of thermal damage on photoelectric performance is reduced. Further, through the second laser annealing treatment, on the basis of the first laser annealing treatment, the microstructure of the cutting surface 31 is further improved, and the regions of the cutting surface 31 that are not treated by the first laser annealing treatment are supplemented, to ensure the uniformity and integrity of the annealing effect. It can not only eliminate the hydroxyl and defects generated after the oxidation edge of the cutting surface 31 is passivated, improve the annealing uniformity, and improve the yield of photovoltaic modules, but also avoid directly irradiating the cutting surface 31 with laser, which may cause excessive energy and damage other film layers of the cut cell 3, without damaging the overall structure of the cell.

[0067] Referring to Figure 2 In the embodiment, the solar cell is specifically a TOPCon solar cell, and the solar cell is divided into two identical cut cells 3, i.e., half cells, by laser scribing. The cutting surface 31 is formed on the edge of one side of the two cut cells 3. The assembly cell made in a series and parallel manner has the advantages of reducing current, reducing resistance loss, improving module voltage, and improving module output power.

[0068] In order to reduce the adverse effects of a large number of dangling bonds and impurities brought by the cutting surface 31 of the edge of the cut cell 3 on the cut cell 3, a layer of oxide film 32, i.e., a passivation layer, is plated on the surface of the cutting surface 31 of the cut cell 3 in the embodiment, to provide field passivation effect, thereby reducing recombination of minority carriers and reducing reflectivity. However, in the process of edge passivation with water vapor as the oxygen source, hydroxyl and some defects will be generated. Therefore, laser annealing is needed after plating to activate the hydrogen passivation inside the cut cell 3 and eliminate the hydroxyl and defects generated in the edge passivation.

[0069] Referring to Figure 3 As shown in the figure, the laser annealing device of the embodiment has a cavity 1, and the device comprises:

[0070] A conveying device 4 is arranged in the cavity 1 and is used to convey the cut cell stack.

[0071] A laser 5 is arranged in the cavity 1 and above the conveying device 4. The laser 5 is arranged obliquely at an angle of 30-60 degrees with the horizontal line, so that the emitted laser light is irradiated on the first area 2 and / or the second area 7 at an angle of 30-60 degrees.

[0072] The conveying device 4 is a conveyor belt device. The laser 5 is arranged above the conveying device 4. During laser annealing, different sliced batteries 3 are stacked into a stack and placed on the conveyor belt of the conveying device 4. The laser 5 is arranged obliquely, so that the emitted laser light is at an angle of 30-60 degrees with the horizontal line, such as 30 degrees, 45 degrees, 60 degrees, etc. In this embodiment, the emitted laser light is at an angle of 45 degrees with the horizontal line, so that the laser light can avoid directly irradiating the cutting surface 31 of the sliced battery 3, causing excessive energy to damage other film layers of the sliced battery 3 without damaging the overall structure. However, the hydroxyl and defects generated after passivation of the cutting surface 31 can be eliminated, the annealing uniformity can be improved, and the yield of photovoltaic modules can be improved. The laser light emitted by the laser 5 is irradiated on the first area 2 and / or the second area 7 at an angle of 30-60 degrees with the horizontal line, avoiding direct irradiation of the cutting surface 31 by the laser beam. The laser annealing effect is more uniform, the hydroxyl and defects generated after passivation of the cutting surface 31 of the sliced battery 3 are eliminated, and the amorphous silicon film layer will not be damaged, and the defects in the amorphous silicon film will be repaired to some extent. If the angle is too large, the distance between the first area 2 and the second area 7 and the cutting surface 31 at one end will be too short, the internal temperature of the sliced battery 3 will be too high, and the structure of the sliced battery 3 may be damaged. If the angle is too small, the internal temperature of the sliced battery 3 may be too low, and the annealing may be uneven.

[0073] In some embodiments, the cavity 1 is provided with a discharge system 6. The discharge system 6 is a pipeline connecting the cavity 1 with the outside, and is fixed to the side wall of the laser annealing device, for discharging waste gas generated in the cavity 1.

[0074] During the first laser annealing, the laser light emitted by the laser 5 irradiates the first area 2. After the first laser annealing, the same stack of sliced batteries 3 is turned over by 180 degrees, so that the sliced batteries 3 previously located at the bottom are replaced by the top. At this time, the laser light emitted by the laser 5 irradiates the second area 7 of the same stack of sliced batteries 3, and the second laser annealing is performed.

[0075] In this embodiment, the thickness d of the sliced battery 3 is 122 um, the stacking number of a stack of the sliced battery 3 is 40 pieces, the parameters of the first laser annealing and the second laser annealing are the same, and the parameters of the laser for the first laser annealing and the second laser annealing are as follows: the laser power is 62 W, the wavelength is 700-1000 nm, the scanning speed is 3-6 us, and the annealing time is 3-5 us. The heating temperature of the first region 2 by the first laser annealing and the heating temperature of the second region 7 by the second laser annealing are both 278°C.

[0076] After the two laser annealings are completed, the surface structure of the sliced battery 3 subjected to the laser annealing in this embodiment is observed by scanning electron microscopy, and an SEM image is taken as shown in FIG. 6. Figure 4

[0077] Through the first laser annealing, the microstructure of the cutting surface 31 is preliminarily improved, the thermal damage and micro-defects generated in the laser cutting process are reduced, the surface roughness is reduced, the residual stress generated during cutting is eliminated, and the grains are refined, so that the microstructure of the cutting surface 31 is improved, and the influence of thermal damage on photoelectric performance is reduced.

[0078] Through the second laser annealing, the microstructure of the cutting surface 31 is further improved on the basis of the first laser annealing, and the regions of the cutting surface 31 that are not treated by the first laser annealing are supplemented, so as to ensure the uniformity and integrity of the annealing effect.

[0079] Therefore, by performing the two laser annealings on the first region 2 and the second region 7, the laser annealing effect on the sliced battery 3 is more uniform, the hydroxyl groups and defects generated after the passivation of the cutting surface 31 of the sliced battery 3 can be eliminated without affecting the edge passivation effect, the amorphous silicon film layer will not be damaged, and the defects in the amorphous silicon film can be repaired to a certain extent. The film layer of the sliced battery 3 is well maintained, and complete tunneling layer and film layer results can be observed.

[0080] In some embodiments, the first region 2 and the second region 7 are 1-2 mm away from the cutting surface 31 on the side away from the cutting surface 31.

[0081] ​such as 1 mm, 1.5 mm, 1.8 mm, 2 mm, etc. The laser of the first laser annealing treatment and the second laser annealing treatment only irradiates the stronger end of the oxide film layer 32, and there is no need to heat the whole sliced battery 3 by laser, which greatly improves the production efficiency and has a good elimination effect on the hydroxyl and defects generated in the edge passivation area, while basically having no effect on other areas. It should be emphasized that the first laser annealing treatment and the second laser annealing treatment do not directly irradiate the cutting surface 31. When irradiating the first area 2 and the second area 7, part of the laser energy acts on the cutting surface 31 to eliminate the hydroxyl and defects generated after the passivation of the cutting surface 31, and will not damage other film layers of the sliced battery 3, such as the tunnel oxide layer, the polysilicon layer or the amorphous silicon layer, and the anti-reflection layer, etc.

[0082] In some embodiments, the laser power of the first laser annealing treatment and the second laser annealing treatment is the same;

[0083] Preferably, the laser power of the first laser annealing treatment and the second laser annealing treatment is 55-68 W, and the heating temperature of the first area 2 by the first laser annealing treatment and the heating temperature of the second area 7 by the second laser annealing treatment are both 275-280℃.

[0084] For example, the laser power of the first laser annealing treatment and the second laser annealing treatment is 55 W, 56 W, 57 W, 58 W, 59 W, 60 W, 61 W, 62 W, 63 W, 64 W, 65 W, 66 W, 68 W, etc., and the heating temperature of the first area 2 by the first laser annealing treatment and the heating temperature of the second area 7 by the second laser annealing treatment are 275℃, 276℃, 277℃, 278℃, 279℃, 280℃, etc.

[0085] The type of laser is pulse laser, and the power, wavelength, scanning speed, scanning path and annealing time of the laser can be set according to the specific thickness and quantity of the sliced battery 3 to ensure the annealing effect. When the laser energy just makes the oxide film layer 32 on the surface of the sliced battery 3 completely melt, a small amount of solid Si particles will be left at the interface between the silicon wafer substrate and the oxide film layer 32, which will grow upwards from the bottom of the oxide film layer 32 in the form of seed crystal, which is called super lateral growth. A proper temperature gradient can promote the growth of such seed crystal, further improve the crystal quality and performance of the oxide film layer 32, and the uneven distribution of particles in the oxide film layer 32 may cause scattering of carriers, thereby affecting the conductivity of the oxide film layer 32.

[0086] Excessive laser power can cause serious damage to the internal structure of the sliced battery 3, and even cause the sliced battery 3 to be "burnt". And the low laser power cannot promote the solid Si particles to grow from the bottom of the oxide film layer 32 in the form of a seed crystal, improve the crystal quality and performance of the oxide film layer 32. Therefore, when the laser power of the first laser annealing treatment and the second laser annealing treatment is 55-68W, the heating temperature of the first region 2 by the first laser annealing treatment, and the heating temperature of the second region 7 by the second laser annealing treatment are in the range of 275-280℃, after two laser annealing, the surface of the oxide film layer 32 becomes more dense, the particle distribution is more uniform and there is no abnormal growth, which means that the quality of the oxide film layer 32 is improved, so as to reduce the generation of hydroxyl and defects in the passivation process, and there is no damage to the internal structure of the sliced battery 3.

[0087] In some embodiments, the laser power of the second laser annealing is lower than the laser power of the first laser annealing;

[0088] Preferably, the laser power of the first laser annealing treatment is 55-68W, and the heating temperature of the first region by the first laser annealing treatment is 275-280℃; the laser power of the second laser annealing treatment is 30-50W, and the heating temperature of the second region by the second laser annealing treatment is 250-255℃.

[0089] For example, when the laser power of the first laser annealing treatment is 55W, 56W, 57W, 58W, 59W, 60W, 61W, 62W, 63W, 64W, 65W, 66W, 68W, etc., the heating temperature of the first region 2 by the first laser annealing treatment is 275℃, 276℃, 277℃, 278℃, 279℃, 280℃, etc., the laser power of the second laser annealing treatment is 30W, 33W, 35W, 40W, 41W, 42W, 43W, 45W, 48W, 50W, etc., and the heating temperature of the second region 7 by the second laser annealing treatment is 250℃, 251℃, 252℃, 253℃, 254℃, 255℃, etc.

[0090] After the first laser annealing treatment, the microstructure of the surface of the cutting surface 31 has been improved to a certain extent. The annealing effect of the slice battery 3 at the bottom of the stack may be slightly lower than that of the slice battery 3 at the top. After turning over, since the slice battery 3 has been treated by the first laser annealing treatment, the power of the laser in the second laser annealing treatment is appropriately reduced, and the heating temperature is also appropriately reduced, which is beneficial to further improve the uniformity of annealing and reduce the structural damage of the slice battery 3 caused by laser annealing treatment, greatly reduce the generation of hydroxyl and defects of the aluminum oxide film layer 32, and will not cause damage to the amorphous silicon film layer, and can repair defects in the amorphous silicon film to a certain extent.

[0091] In some embodiments, the thickness d of the slice battery 3 is 120-123um, such as 120um, 121um, 122um or 123um, etc. The number of stacks of the slice battery 3 is 30-50, such as 30, 35, 40, 45 or 50, etc.

[0092] In some embodiments, the annealing method further comprises a performance detection step of the slice battery 3 after the second laser annealing treatment. When the performance detection finds that the performance of the slice battery 3 after the second laser annealing treatment is unqualified, the unqualified slice battery 3 repeats the first laser annealing treatment and the second laser annealing treatment until the performance detection of the slice battery 3 is qualified.

[0093] Preferably, the performance detection includes detecting at least one of the appearance, EL, open pressure, current, fill factor, photoelectric conversion efficiency and yield rate of the slice battery 3. The appearance refers to the appearance pass rate of the slice battery 3, that is, the ratio of the slice battery 3 without defects to the total number of slice batteries 3. EL refers to the number of microstructures without defects in the slice battery 3 after electroluminescence to the total number of slice batteries 3. Open pressure refers to the minimum open circuit voltage of the slice battery 3 under no external force. Current refers to the current intensity when passing through a slice battery 3, and the current size determines the output power of the slice battery 3. Fill factor refers to the ratio of the maximum power of the slice battery 3 to the product of its open circuit voltage and short circuit current. The yield rate refers to the percentage of the number of qualified slice batteries in the total number of slice batteries detected in the detection process.

[0094] The performance of the sliced battery 3 after the second laser annealing treatment is detected to test the effect of the twice annealing treatment, and the qualified sliced battery 3 is screened out, and the unqualified sliced battery 3 is repeatedly subjected to laser annealing treatment to increase the annealing qualified rate of the sliced battery 3. The appearance, EL, open voltage, current, fill factor, photoelectric conversion efficiency and yield of the manufactured sliced battery 3 are detected on line, the annealing effect is verified, the qualified sliced battery 3 is screened out, and the accuracy of the electrical performance and El test data of the sliced battery 3 is ensured.

[0095] In this embodiment, the performance detection results of the sliced battery 3 are shown in the following table:

[0096]

[0097] In the above table, the whole piece battery specifically refers to a solar cell which has not been subjected to cutting treatment, that is, a finished battery piece which has not been subjected to any treatment. The difference between the sliced battery 3 after cutting and the whole piece battery before laser annealing refers to the performance difference between the sliced battery 3 after cutting and the finished battery piece before annealing, the surface of which is subjected to passivation coating. The twice laser annealing refers to the performance difference between the sliced battery 3 after the first laser annealing treatment and the second laser annealing treatment and the finished battery piece after the surface is coated with the oxide film layer 32.

[0098] As shown in the above table, the performance of the sliced battery 3 after the twice laser annealing is compared with the difference between the sliced battery 3 before laser annealing and the whole piece battery, the appearance pass rate and the EL pass rate are increased, the current is decreased, the open voltage is increased, the fill factor is increased, the photoelectric conversion efficiency is increased, and the yield is increased, which indicates that the overall performance of the sliced battery 3 after the twice annealing treatment is improved, the sliced battery 3 is qualified, and vice versa, which needs to be repeatedly subjected to annealing treatment.

[0099] In some embodiments, the sliced battery 3 is subjected to cooling treatment before the performance detection, the cooling treatment time is 3.5-5 min, and the final temperature of the cooling treatment is 24-26℃.

[0100] For example, the cooling treatment time is 3.5 min, 4 min, 4.5 min, 5 min, etc., and the final temperature of the cooling treatment is 24℃, 25℃, 25.5℃, 26℃, etc.

[0101] Before the performance test of the sliced battery 3, the cooling time is too long, which has little effect on the sliced battery 3, but prolongs the working hours, and the cooling temperature is too low, which wastes the cooling time and is not conducive to the production efficiency. If the cooling time is too short, the sliced battery 3 cannot be cooled to the ideal temperature, which will cause the sliced battery 3 to frequently alarm during sorting, the temperature is too high, and the sliced battery 3 is frequently stuck during sorting, which is easy to cause part of the sliced battery 3 to be not separated. In the embodiment, the specific cooling time is 4 min, and the final temperature of the cooling treatment is 24.5°C.

[0102] In other embodiments, the sliced battery 3 has one cutting surface 31 or two cutting surfaces 31. Two identical batteries formed by cutting a standard specification battery along a direction perpendicular to the main grid line of the battery using a laser cutting method are called two-sliced batteries, which have one cutting surface 31. Three identical batteries formed by cutting a standard specification battery along a direction perpendicular to the main grid line of the battery using a laser cutting method are called three-sliced batteries, which have two cutting surfaces 31. Similarly, when four, five, etc. identical batteries are formed by cutting a standard specification battery along a direction perpendicular to the main grid line of the battery using a laser cutting method, they are called four-sliced batteries, five-sliced batteries, etc., all of which have two cutting surfaces 31, which increases the scope of application of the method.

[0103] In some embodiments, the laser of the first laser annealing treatment and the second laser annealing treatment has an angle of 30-60 degrees with the horizontal line.

[0104] The laser has an angle of 30-60 degrees with the horizontal line, such as 30 degrees, 45 degrees, 60 degrees, etc., and in the embodiment, the angle is 45 degrees, so as to improve the effect of the laser annealing treatment. The laser emitted by the laser 5 is irradiated on the first area 2 and / or the second area 7 in a manner that the laser has an angle of 30-60 degrees with the horizontal line, which avoids the direct irradiation of the laser beam on the cutting surface 31, can make the laser annealing treatment more uniform, eliminate the hydroxyl and defects generated after the passivation of the cutting surface 31 of the sliced battery 3, and will not cause damage to the amorphous silicon film layer, and to a certain extent, repair the defects in the amorphous silicon film. If the angle is too large, the distance between the first area 2 and the second area 7 and one end of the cutting surface 31 is too short, the internal temperature of the sliced battery 3 is too high, and the structure of the sliced battery 3 may be damaged. If the angle is too small, the internal temperature of the sliced battery 3 may be too low, and the annealing is not uniform.

[0105] In some embodiments, the solar cell is a tunnel oxide passivated (TOPCon) cell, a passivated emitter and rear local contact (PERC) cell, or a crystalline silicon heterojunction solar (HIT) cell.

[0106] The application provides that the annealing method can be applied not only to tunnel oxide passivated cells, but also to passivated emitter and rear local contact cells and crystalline silicon heterojunction solar cells, and can achieve almost the same effect.

[0107] Comparative Example

[0108] A solar cell preparation method, which is different from the embodiment, is that only one laser annealing treatment is performed, and when the laser annealing treatment is performed, one laser beam is used to cover a stack of the cutting surfaces 31 of the sliced cells 3 formed with the passivation layer to perform the laser annealing treatment.

[0109] After the laser annealing is completed, the surface structure of the sliced cells 3 in the present comparative example is also observed by scanning electron microscopy, and the SEM image is as shown in Figure 5 .

[0110] Comparison Figure 4 and Figure 5 It can be concluded that, from the perspective of passivation microstructure, the sliced cells 3 after the annealing treatment are well maintained by the two laser annealing treatments in the embodiment, and the complete tunneling layer, the polycrystalline silicon layer (Poly silicon layer) and the oxide film layer (Si x N y layer) can be seen. However, the sliced cells 3 after the annealing treatment are more severely damaged in the comparative example, the tunneling layer and the polycrystalline silicon layer (Poly silicon layer) of the sliced cells 3 are damaged, and the structure of the oxide film layer (Si x N y layer) of the sliced cells 3 is also damaged to different degrees. Therefore, the sliced cell preparation method provided in the embodiment can eliminate the hydroxyl and defects generated after the passivation of the oxidation edge when the cutting surface 31 is plated with the oxide film layer, improve the annealing uniformity, and improve the yield of photovoltaic modules by respectively performing the first laser annealing treatment and the second laser treatment on the first region 2 and the second region 7 of the sliced cells 3; and can also avoid directly irradiating the cutting surface 31 with the laser, which can cause the energy to be too large to cause damage to the structure of the tunneling layer and the polycrystalline silicon layer (Poly silicon layer) and the oxide film layer (Si x N y layer) of the sliced cells 3, and does not damage the overall structure of the cell.

[0111] The technical features of the above embodiments can be combined in any manner. In order to make the description simple, all possible combinations of the technical features in the above embodiments are not described, but as long as the combination of the technical features does not exist contradictory, it should be considered as the scope of the present disclosure.

[0112] The above-described embodiments are merely illustrative of several embodiments of the present application, which are described in more detail and in a specific manner, but should not be construed as limiting the scope of the patent. It should be noted that for those skilled in the art, several modifications and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application should be subject to the appended claims.

Claims

1. A method for preparing a sliced ​​battery, characterized in that, Includes the following steps: Provide solar cells; The solar cell is cut to obtain a plurality of sliced ​​cells (3), the sliced ​​cells (3) having opposite front and back sides, and at least one cut surface (31) connecting the front and back sides. The cut surface (31) of the sliced ​​battery (3) is passivated, and a passivation layer is formed on the cut surface (31) of the sliced ​​battery (3); A plurality of the sliced ​​batteries (3) are stacked in the same direction with the passivation layers of the sliced ​​batteries (3) facing the same direction to form a sliced ​​battery stack. The first main surface of the sliced ​​battery stack has a first region (2) near the end of the passivation layer, and the second main surface of the sliced ​​battery stack has a second region (7) near the end of the passivation layer. The sliced ​​battery stack is subjected to laser annealing, the laser annealing process including: First laser annealing: The first region (2) of the sliced ​​battery stack is subjected to a first laser annealing process; Flip the stack of sliced ​​batteries; Second laser annealing: The second region (7) of the sliced ​​battery stack is subjected to a second laser annealing process; The lasers used in the first and second laser annealing processes are at an angle of 30-60 degrees to the horizontal line.

2. The method for preparing a sliced ​​battery as described in claim 1, characterized in that, The first region (2) and the second region (7) are 1-2 mm away from the cutting surface (31) on the side away from the cutting surface (31).

3. The method for preparing a sliced ​​battery as described in claim 1, characterized in that, The laser power of the first laser annealing process and the second laser annealing process is the same; the laser power of the first laser annealing process and the second laser annealing process is 55-68W; the heating temperature of the first laser annealing process on the first region (2) and the heating temperature of the second laser annealing process on the second region (7) are both 275℃-280℃.

4. The method for preparing a sliced ​​battery as described in claim 1, characterized in that, The laser power of the second laser annealing process is lower than that of the first laser annealing process; the laser power of the first laser annealing process is 55-68W, and the heating temperature of the first region (2) in the first laser annealing process is 275℃-280℃; the laser power of the second laser annealing process is 30-50W, and the heating temperature of the second region (7) in the second laser annealing process is 250℃-255℃.

5. The method for preparing a sliced ​​battery as described in claim 3, characterized in that, The thickness d of the sliced ​​battery (3) is 120-123um, and the number of sliced ​​batteries (3) stacked in a stack is 30-50 slices.

6. The method for preparing a sliced ​​battery as described in claim 1, characterized in that, The method further includes a performance testing step on the sliced ​​battery (3) after the second laser annealing process. When the performance test finds that the sliced ​​battery (3) after the second laser annealing process is unqualified, the first laser annealing process and the second laser annealing process are repeated on the unqualified sliced ​​battery (3) until the performance test of the sliced ​​battery (3) is qualified.

7. The method for preparing a sliced ​​battery as described in claim 6, characterized in that, The performance testing includes testing at least one of the following: appearance, EL, on-state voltage, current, fill factor, photoelectric conversion efficiency, and yield of the sliced ​​cell (3).

8. The method for preparing a sliced ​​battery as described in claim 6, characterized in that, Before performing performance testing on the sliced ​​battery (3), the sliced ​​battery (3) is first cooled for 3.5-5 minutes, and the final temperature of the cooling process is 24-26°C.

9. The method for preparing a sliced ​​battery as described in claim 1, characterized in that, The sliced ​​battery (3) has one cut surface (31) or two cut surfaces (31).

10. The method for preparing a sliced ​​battery according to any one of claims 1-9, characterized in that, The solar cell is a TOPCon cell, a PERC cell, or a HIT cell.

11. A sliced ​​battery, characterized in that, The sliced ​​battery (3) is prepared by the sliced ​​battery preparation method according to any one of claims 1-10.

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