Slice battery and preparation method and equipment thereof

Abstract

The invention belongs to the field of crystalline silicon solar cells, and relates to a slice cell and a preparation method and equipment thereof, and the preparation method comprises the steps: providing a solar cell; cutting the solar cell to obtain a slice cell which has a front surface, a back surface and a cutting surface; passivating the cutting surface to form a passivation layer; the slice batteries are stacked into a slice battery stack in the mode that the passivation layers face the same direction, the end, close to the passivation layers, of the first main surface of the slice battery stack is provided with a first area, and the end, close to the passivation layers, of the second main surface of the slice battery stack is provided with a second area; carrying out first laser annealing treatment on the first area; overturning the sliced battery stack; and carrying out second laser annealing treatment on the second area. The first region and the second region are subjected to two-time separated laser annealing treatment, so that hydroxyl groups and defects generated when an oxide film layer is plated are eliminated, the annealing uniformity is improved, the yield of a photovoltaic module is improved, and the overall structure of a solar cell is not damaged.

Description

Technical Field

[0001] The present application relates to the technical field of crystalline silicon solar cells, and in particular to a sliced ​​cell and a preparation method and equipment thereof. Background Art

[0002] Since half-cells have the advantages of reducing current, lowering resistance, increasing the voltage of photovoltaic modules, and improving the output power of photovoltaic modules, when making edge passivated solar cells, it is usually necessary to split a complete cell into multiple half-cells, and then make modules by connecting the half-cells in series and parallel. Half-cell technology is a technology that cuts standard specification cells (156mmx156mm) into two pieces (156x78mm) by laser, and then connects them after cutting. The cells of the entire photovoltaic module are then divided into two groups, each group contains 60 sliced ​​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, and the internal loss is reduced to 1 / 4 of the whole cell, thereby increasing the power of the photovoltaic module.

[0003] In industrial applications, there are various ways to cut solar cells, including laser slicing, water-free slicing, etc. However, no matter which method is used, due to the interaction between the cutting tool and the cutting fluid, tiny damage and defects are generated on the surface of the silicon wafer. These damages and defects will increase the surface recombination rate of the side section of the silicon wafer after cutting, 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 solar cells. Among them, the laser cutting process often brings a large number of dangling bonds and impurities. Dangling bonds refer to unpaired chemical bonds generated on the surface of semiconductor materials due to the destruction of the periodic structure of the lattice. These dangling bonds will not only increase the defect state density on the surface of crystalline silicon, but also affect the electrochemical properties of the cell, specifically the passivation performance, which has a serious impact on the minority carrier lifetime of the cell. For example, when cutting TOPCon solar cells using laser slicing, the cross section is usually a non-passivated silicon wafer cross section, which increases the edge recombination of the cut surface, resulting in a significant decrease in the cell conversion efficiency.

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

[0005] Therefore, in order to improve battery efficiency, passivation coating of the cut surface is a better choice. However, in the process of edge passivation aluminum oxide coating with water vapor as the oxygen source, hydroxyl groups and some defects such as melting, notches or microcracks will be generated. Therefore, an annealing step is generally added after passivation to activate hydrogen passivation inside the battery and eliminate the defects caused by edge passivation. Unlike ordinary annealing methods, the principle of laser annealing is to use a laser beam to irradiate the semiconductor surface, generate extremely high temperatures in the irradiated area, repair the damage to the crystal, and eliminate dislocations.

[0006] However, the current laser annealing method has the problem of uneven annealing, and its effect on eliminating passivation defects is also relatively limited. Summary of the invention

[0007] Based on this, a sliced ​​battery and a preparation method and equipment thereof are provided. By performing a first laser annealing treatment and a second laser treatment on the first area and the second area of ​​the sliced ​​battery respectively, the hydroxyl groups and defects generated after the oxidation edge passivation when the cut surface is plated with an oxide film are eliminated, the annealing uniformity is improved, and the yield rate of photovoltaic modules is improved without destroying the overall structure of the battery.

[0008] On the one hand, a method for preparing a sliced ​​battery is provided, comprising the following steps:

[0009] Provide solar cells;

[0010] Cutting the solar cell to obtain a plurality of sliced ​​cells, wherein the sliced ​​cells have a front side and a back side opposite to each other, and at least one cutting surface connecting the front side and the back side;

[0011] Performing a passivation treatment on the cut surface of the sliced ​​battery to form a passivation layer on the cut surface of the sliced ​​battery;

[0012] Stacking a plurality of the sliced ​​batteries into a sliced ​​battery stack in a manner that the passivation layers of the sliced ​​batteries face the same direction, wherein a first main surface of the sliced ​​battery stack close to one end of the passivation layer has a first region, and a second main surface of the sliced ​​battery stack close to one end of the passivation layer has a second region;

[0013] The sliced ​​battery stack is subjected to laser annealing treatment, wherein the laser annealing treatment comprises:

[0014] First laser annealing treatment: performing a 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 a 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 laser power of the second laser annealing process are the same;

[0019] Preferably, the laser powers of the first laser annealing treatment and the second laser annealing treatment are both 55-68W, the heating temperature of the first region by the first laser annealing treatment and the heating temperature of the second region by the second laser annealing treatment are both 275° C.-280° C.;

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

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

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

[0023] In one embodiment, the step of performing a performance test on the sliced ​​battery after the second laser annealing treatment is completed is also included. When the performance test finds that the performance of the sliced ​​battery after the second laser annealing treatment is unqualified, the unqualified sliced ​​battery repeats the first laser annealing treatment and the second laser annealing treatment until the performance test of the sliced ​​battery is qualified.

[0024] Preferably, the performance test includes testing at least one of the appearance, EL, opening voltage, current, fill factor, photoelectric conversion efficiency and yield rate of the sliced ​​battery.

[0025] In one of the embodiments, the sliced ​​battery is cooled before the performance test, the cooling time is 3.5-5 minutes, and the final temperature of the cooling is 24-26°C.

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

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

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

[0029] On the other hand, a sliced ​​battery is provided, wherein the sliced ​​battery is prepared by any one of the preparation methods described above.

[0030] On the other hand, a laser annealing device is provided, which is used in the laser annealing step in any one of the above-mentioned sliced ​​battery preparation methods, and the device has a cavity, and the device includes:

[0031] A transmission device, disposed in the cavity, for transmitting the sliced ​​battery stack;

[0032] The laser is arranged in the cavity and located above the transmission device. The laser is tilted and forms an angle of 30-60 degrees with the horizontal line, so that the emitted laser irradiates the first area and / or the second area at an angle of 30-60 degrees.

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

[0034] The method for preparing sliced ​​batteries provided in an embodiment of the present invention is based on the mutual compensation of a first laser annealing treatment on the first main surface of the sliced ​​battery stack and a second laser annealing treatment on the second main surface. It can not only ensure uniform annealing of the cut surface of the sliced ​​battery, but also completely eliminate the defects caused by passivation of the cut surface of the sliced ​​battery, and will not damage other film layers of the sliced ​​battery, thereby protecting the overall structure of the sliced ​​battery.

[0035] The present invention obtains sliced ​​cells by cutting solar cells, and passivates the cut surfaces of the sliced ​​cells to form a passivation layer, thereby reducing the adverse effects of a large number of dangling bonds and impurities on the sliced ​​cells brought by the cut surfaces, and then performs a first laser annealing treatment and a second laser treatment on the first region and the second region of the sliced ​​cells respectively. Through the first laser annealing treatment, the microstructure of the cut surface is preliminarily improved, the thermal damage and micro defects generated during the laser cutting process are reduced, the surface roughness is reduced, the residual stress generated during cutting is eliminated, and the grains begin to be refined, so that the microstructure of the cut surface surface is improved, and the influence of thermal damage on the photoelectric performance is reduced; further, through the second laser annealing treatment, on the basis of the first laser annealing treatment, the microstructure of the cut surface is further improved, and the cut surface area not treated by the first laser annealing treatment is supplemented, so as to ensure the uniformity and integrity of the annealing effect; the hydroxyl groups and defects generated after the passivation of the oxidized edge of the cut surface can be eliminated, the annealing uniformity can be improved, and the yield rate of the photovoltaic module can be improved; and the cut surface can be avoided from being directly irradiated with a laser, resulting in excessive energy causing damage to other film layers of the sliced ​​cell, without destroying the overall structure of the cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 A flow chart of an annealing method provided in one embodiment of the present invention;

[0037] Figure 2 A schematic diagram of the structure of a sliced ​​battery provided by an embodiment of the present invention, wherein reference numerals 2 and 7 denote two opposite surfaces;

[0038] Figure 3 A schematic diagram of a process for laser annealing provided in one embodiment of the present invention;

[0039] Figure 4 A SEM image of a half-cell battery after annealing by the annealing method provided in one embodiment of the present invention;

[0040] Figure 5 This is a SEM image of a half-cell after annealing treatment using a proportional annealing method of the present invention.

[0041] Reference numerals

[0042] 1. Cavity; 2. First area; 3. Sliced ​​battery; 31. Cutting surface; 32. Oxide film layer; 4. Transmission device; 5. Laser; 6. Emission system; 7. Second area. DETAILED DESCRIPTION

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

[0044] It should be noted that the illustrations provided in this embodiment are only used to illustrate the basic concept of the present invention in a schematic manner. Therefore, the drawings only show components related to the present invention rather than being drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component may be changed arbitrarily, and the component layout may also be more complicated.

[0045] The structures, proportions, sizes, etc. illustrated in the drawings of this specification are only used to match the contents disclosed in the specification so as to facilitate understanding and reading by persons familiar with this technology. They are not used to limit the conditions under which the present invention can be implemented, and therefore have no substantive technical significance. Any structural modification, change in proportion or adjustment of size, without affecting the effects and purposes that can be achieved by the present invention, should still fall within the scope of the technical contents disclosed by the present invention.

[0046] The directions or positional relationships indicated by the terms "upper", "lower", "left", "right", "middle", "longitudinal", "lateral", "horizontal", "inner", "outer", "radial", "circumferential" and the like in this specification are based on the directions or positional relationships shown in the drawings and are only for the convenience of simplifying the description. They do not indicate or imply that the devices or elements referred to must have a specific direction, be constructed and operate in a specific direction, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance.

[0047] At present, the main method of laser annealing the cut surface of the battery is: a beam of laser directly irradiates the cut surface of the battery for annealing, and the laser covers the entire cut surface. When the applicant annealed the cut surface of the half-cell battery according to this existing annealing method, it was found that there was uneven annealing and the effect of eliminating edge passivation defects was relatively limited. And from the perspective of the passivation microstructure, the structure of the half-cell battery after annealing was severely damaged, the tunneling oxide layer and polycrystalline (poly) silicon layer of the half-cell battery were completely destroyed, and the membrane structure of the half-cell battery was also damaged to varying degrees.

[0048] In order to eliminate the hydroxyl groups and defects generated after the edge passivation of the half-cell while reducing the damage to the overall structure of the half-cell, thereby improving the yield rate of photovoltaic modules and achieving the purpose of reducing costs and increasing efficiency, the applicant attempts to analyze the reasons why the existing annealing method has the above problems.

[0049] The study found that when laser annealing half-cell batteries, in order to improve the annealing efficiency, multiple half-cell batteries are stacked into a neat stack, with the cut surfaces of the stack of half-cell batteries facing the same side. The cut surfaces are passivated to form a passivation layer, and then the top surface of the entire stack of half-cell batteries close to the cut surface is laser irradiated for annealing. However, due to the certain thickness of a stack of half-cell batteries, the laser energy is unevenly distributed after penetrating the upper half-cell battery during laser annealing, thus affecting the annealing effect of the middle and lower half-cell batteries. If the annealing effect of the middle and lower half-cell batteries is improved by increasing the laser power or extending the laser irradiation time, the upper half-cell battery will overheat, and it is impossible to find suitable laser parameters. Therefore, the current annealing method of using only one laser beam to irradiate the top surface of the entire stack of half-cells close to the cutting surface will result in uneven annealing in different areas of the half-cells, causing serious damage to the structure of some half-cells, destroying the tunneling oxide layer and polycrystalline (poly) silicon layer of the half-cells, and causing varying degrees of damage to the film structure. The effect of eliminating edge passivation defects is also relatively limited.

[0050] Based on this, we tried to perform laser annealing on different areas of the half-cell. The results showed that laser annealing on different areas can not only better eliminate the hydroxyl groups and defects produced by the passivation of the oxidation edge during oxide film coating, thereby improving the yield rate of photovoltaic modules and achieving the goal of reducing costs and increasing efficiency, but also will not damage the overall structure of the half-cell.

[0051] The half-cell battery described in the present invention refers to: using a laser cutting method to cut a standard specification battery in a direction perpendicular to the battery main grid line to form two identical batteries, and therefore, it is also called a two-piece battery; each half-cell battery has a cutting surface.

[0052] The three-piece battery described in the present invention refers to: using the laser cutting method to cut a standard specification battery in a direction perpendicular to the battery main grid line to form three identical batteries, and each three-piece battery has two cutting surfaces. Similarly, when using the laser cutting method to cut a standard specification battery in a direction perpendicular to the battery main grid line to form four, five, etc. identical batteries, it is called a four-piece battery, a five-piece battery, etc., and all have two cutting surfaces.

[0053] The first main surface of the sliced ​​battery stack described in the present invention refers to: the surface of the sliced ​​battery stack on one side along the sliced ​​battery stacking direction, that is, one of the two surfaces of the sliced ​​battery stack with the largest area, located on one of the outermost sliced ​​batteries in the sliced ​​battery stack.

[0054] The second main surface of the sliced ​​battery stack described in the present invention refers to: the surface of the sliced ​​battery stack on the other side along the sliced ​​battery stacking direction, that is, the other surface of the two surfaces with the largest area of ​​the sliced ​​battery stack, located on the other sliced ​​battery on the outermost side of the sliced ​​battery stack.

[0055] Example

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

[0057] Provide solar cells;

[0058] Cutting the solar cell to obtain a plurality of sliced ​​cells 3, wherein the sliced ​​cells 3 have a front side and a back side opposite to each other, and at least one cutting surface 31 connecting the front side and the back side;

[0059] Performing a passivation treatment on the cut surface 31 of the sliced ​​battery 3 to form a passivation layer on the cut surface 31 of the sliced ​​battery 3;

[0060] Stacking a plurality of the sliced ​​batteries 3 into a sliced ​​battery stack in a manner that the passivation layers of the sliced ​​batteries 3 face the same direction, wherein a first main surface of the sliced ​​battery stack close to one end of the passivation layer has a first region 2, and a second main surface of the sliced ​​battery stack close to one end of the passivation layer has a second region 7;

[0061] The sliced ​​battery stack is subjected to laser annealing treatment, wherein the laser annealing treatment comprises:

[0062] First laser annealing treatment: performing a 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: a second laser annealing treatment is performed on the second region 7 of the sliced ​​battery stack.

[0065] The preparation method of the sliced ​​battery provided in an embodiment of the present invention is 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. It 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, thereby protecting the overall structure of the sliced ​​battery 3.

[0066] Specifically, the present invention obtains a sliced ​​cell 3 by cutting a solar cell, performs a passivation treatment on the cut surface 31 of the sliced ​​cell 3 to form a passivation layer, reduces the adverse effects of a large number of dangling bonds and impurities brought by the cut surface 31 on the sliced ​​cell 3, and then performs a first laser annealing treatment and a second laser treatment on the first region 2 and the second region 7 of the sliced ​​cell 3 respectively. Through the first laser annealing treatment, the microstructure of the cut surface 31 is preliminarily improved, the thermal damage and micro defects generated during the laser cutting process are reduced, the surface roughness is reduced, the residual stress generated during cutting is eliminated, and the grains are initially refined, so that the cut surface The microstructure of the surface of 31 is improved, reducing the influence of thermal damage on the photoelectric performance; further, through the second laser annealing treatment, on the basis of the first laser annealing treatment, the microstructure of the cut surface 31 is further improved, and the area of ​​the cut surface 31 not treated by the first laser annealing treatment is supplemented to ensure the uniformity and integrity of the annealing effect; it can eliminate the hydroxyl groups and defects generated by the passivation of the oxidized edge of the cut surface 31, improve the annealing uniformity, and improve the yield rate of photovoltaic modules; it can also avoid directly irradiating the cut surface 31 with laser, resulting in excessive energy causing damage to other film layers of the sliced ​​battery 3, without destroying the overall structure of the battery.

[0067] Reference Figure 2 In this embodiment, the solar cell is specifically a TOPCon solar cell, which is divided by laser scribing to form two identical sliced ​​cells 3, i.e., half-cells. A cutting surface 31 is formed at the edge of the side where the two sliced ​​cells 3 are separated. The module battery made by connecting the sliced ​​cells 3 in series and in parallel has the advantages of reducing current, reducing resistance, increasing module voltage, and improving module output power.

[0068] In order to reduce the adverse effects of a large number of dangling bonds and impurities on the sliced ​​battery 3 brought by the cut surface 31 at the edge of the sliced ​​battery 3, a layer of oxide film 32, i.e., a passivation layer, is plated on the surface of the cut surface 31 of the sliced ​​battery 3 in this embodiment to provide a field passivation effect, thereby reducing minority carrier recombination and reducing reflectivity. However, when water vapor is used as an oxygen source, hydroxyl groups and some defects will be generated during the edge passivation process. Therefore, laser annealing is required after coating to activate hydrogen passivation inside the sliced ​​battery 3 and eliminate hydroxyl groups and defects generated by edge passivation.

[0069] Reference Figure 3 As shown, the laser annealing device of this embodiment has a cavity 1, and the device includes:

[0070] A transmission device 4, disposed in the cavity 1, for transmitting the sliced ​​battery stack;

[0071] The laser 5 is arranged in the cavity 1 and is located above the transmission device 4. The laser 5 is tilted and forms an angle of 30-60 degrees with the horizontal line, so that the emitted laser irradiates the first area 2 and / or the second area 7 at an angle of 30-60 degrees.

[0072] The transmission device 4 is a conveyor belt device, and the laser 5 is arranged above the transmission device 4. When performing laser annealing treatment, different sliced ​​batteries 3 are stacked into stacks and placed on the conveyor belt of the transmission device 4. The laser 5 is tilted so that the emitted laser is at an angle of 30-60 degrees to the horizontal line, such as 30 degrees, 45 degrees, 60 degrees, etc. In this embodiment, the emitted laser is 45 degrees to the horizontal line so that the laser can avoid directly irradiating the cutting surface 31 of the sliced ​​battery 3, resulting in excessive energy causing damage to other film layers of the sliced ​​battery 3 without destroying the overall structure; but it can eliminate the hydroxyl groups and defects generated after the oxidation edge passivation of the cutting surface 31, improve the annealing uniformity, and improve the yield rate of photovoltaic modules. The laser emitted by the laser 5 is irradiated on the first region 2 and / or the second region 7 at an angle of 30-60 degrees to the horizontal line, avoiding direct irradiation of the laser beam on the cut surface 31, which can make the laser annealing treatment effect more uniform, eliminate the hydroxyl groups and defects generated after the passivation of the cut surface 31 at the edge of the sliced ​​battery 3, and will not cause damage to the amorphous silicon film layer, and repair the defects in the amorphous silicon film to a certain extent. If the angle is too large, the distance between the first region 2 and the second region 7 and one end of the cut surface 31 is too short, and the internal temperature of the sliced ​​battery 3 is too high, which may cause the structural damage of the sliced ​​battery 3. If the angle is too small, the internal temperature of the sliced ​​battery 3 may be too low, resulting in uneven annealing.

[0073] In some embodiments, the cavity 1 is provided with an exhaust system 6 , which is a pipe connecting the cavity 1 with the outside and fixed on the side wall of the laser annealing equipment to discharge the exhaust gas generated in the cavity 1 .

[0074] During the first laser annealing treatment, the laser emitted by the laser 5 irradiates the first area 2. After the first laser annealing treatment is completed, the same stack of sliced ​​batteries 3 is flipped 180° so that the sliced ​​batteries 3 previously located at the bottom are moved to the top. At this time, the laser emitted by the laser 5 irradiates the second area 7 of the same stack of sliced ​​batteries 3 for the second laser annealing treatment.

[0075] In this embodiment, the thickness d of the sliced ​​battery 3 is 122um, the number of sliced ​​batteries 3 stacked in a stack is 40, the parameters of the first laser annealing are the same as the parameters of the second laser annealing, and the parameters of the laser for the first laser annealing and the second laser annealing are specifically: laser power is 62W, wavelength is 700-1000nm, scanning speed is 3-6us, annealing time is 3-5us, the heating temperature of the first laser annealing treatment on the first area 2 and the heating temperature of the second laser annealing treatment on the second area 7 are 278°C.

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

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

[0078] Through the second laser annealing treatment, on the basis of the first laser annealing treatment, the microstructure of the cut surface 31 is further improved, and the area of ​​the cut surface 31 not treated by the first laser annealing treatment is supplemented, thereby ensuring the uniformity and integrity of the annealing effect.

[0079] Therefore, by performing laser annealing treatment twice on the first area 2 and the second area 7, the laser annealing treatment effect on the sliced ​​battery 3 is made more uniform. The hydroxyl groups and defects generated after the passivation of the edge 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 the complete tunneling layer and film layer results can be seen.

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

[0081] Such as 1mm, 1.5mm, 1.8mm, 2mm, 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 perform laser heating on the entire sliced ​​battery 3, which greatly improves the production efficiency and has a good effect of eliminating the hydroxyl groups and defects generated in the edge passivation area, while having little 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 cut surface 31. When irradiating the first area 2 and the second area 7, part of the laser energy acts on the cut surface 31 to eliminate the hydroxyl groups and defects generated after the passivation of the cut surface 31, and will not damage other film layers of the sliced ​​battery 3, such as the tunneling oxide layer, the polysilicon layer or the amorphous silicon layer and the anti-reflection layer.

[0082] In some embodiments, the laser powers of the first laser annealing process and the second laser annealing process are the same;

[0083] Preferably, the laser powers of the first laser annealing treatment and the second laser annealing treatment are both 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 both 275° C.-280° C.;

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

[0085] The type of laser is pulsed laser, and the parameters such as laser power, wavelength, scanning speed, scanning path and annealing time can be set according to the specific thickness and number 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 remain at the interface between the silicon wafer substrate of the sliced ​​battery 3 and the oxide film layer 32. These particles will grow upward from the bottom of the oxide film layer 32 in the form of seed crystals, which is called super lateral growth. Appropriate temperature gradient can promote the growth of such seed crystals, further improve the crystal quality and performance of the oxide film layer 32, and the particle distribution in the oxide film layer 32 is relatively uneven, which may cause carrier scattering, thereby affecting the conductive properties of the oxide film layer 32.

[0086] Too high laser power will cause serious damage to the internal structure of the sliced ​​battery 3, and even cause the sliced ​​battery 3 to "burn". However, too low laser power cannot promote the growth of solid Si particles from the bottom of the oxide film layer 32 in the form of seed crystals, thereby improving 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 laser annealing treatment for the first region 2 and the heating temperature of the second laser annealing treatment for the second region 7 are in the range of 275-280°C. After two laser annealings, the surface of the oxide film layer 32 becomes denser, the particle distribution is more uniform and there is no abnormal growth, which means that the quality of the oxide film layer 32 has been improved, thereby reducing the generation of hydroxyl groups and defects during the passivation process, and does not damage 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 area by the first laser annealing treatment is 275°C-280°C; the laser power of the second laser annealing treatment is 30-50W, and the heating temperature of the second area by the second laser annealing treatment is 250°C-255°C.

[0089] For example, 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°C, 276°C, 277°C, 278°C, 279°C, 280°C, 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°C, 251°C, 252°C, 253°C, 254°C, 255°C, etc.

[0090] After the first laser annealing treatment, the microstructure of the surface of the cut surface 31 has been improved to a certain extent. The annealing effect of the sliced ​​battery 3 at the bottom of a stack of sliced ​​batteries 3 may be slightly lower than that of the sliced ​​battery 3 at the top. After flipping, since this part of the sliced ​​batteries 3 has passed the first laser annealing treatment, the laser power and heating temperature are appropriately reduced during the second laser annealing treatment, which is beneficial to further improve the uniformity of annealing and reduce the structural damage of the sliced ​​batteries 3 caused by the laser annealing treatment, and greatly reduce the hydroxyl groups and defects generated by the aluminum oxide film layer 32, without causing damage to the amorphous silicon film layer, and can repair the defects in the amorphous silicon film to a certain extent.

[0091] In some embodiments, the thickness d of the sliced ​​battery 3 is 120-123um, such as 120um, 121um, 122um or 123um, etc., and the number of stacks of the sliced ​​batteries 3 in a stack is 30-50 pieces, such as 30 pieces, 35 pieces, 40 pieces, 45 pieces or 50 pieces, etc.

[0092] In some embodiments, the annealing method further comprises a step of performing a performance test on the sliced ​​battery 3 after the second laser annealing treatment is completed. When the performance test finds that the performance of the sliced ​​battery 3 after the second laser annealing treatment is unqualified, the unqualified sliced ​​battery 3 repeats the first laser annealing treatment and the second laser annealing treatment until the performance test of the sliced ​​battery 3 is qualified;

[0093] Preferably, the performance test includes testing at least one of the appearance, EL, opening voltage, current, filling factor, photoelectric conversion efficiency and yield rate of the sliced ​​battery 3. Among them, appearance refers to the appearance pass rate of the sliced ​​battery 3 for testing, that is, the ratio of the sliced ​​battery 3 with no defects in appearance to the total number of sliced ​​batteries 3. EL refers to the ratio of the number of sliced ​​batteries 3 without microscopic defects to the total number of sliced ​​batteries 3 after the sliced ​​battery 3 undergoes electroluminescence. Opening voltage refers to the minimum open circuit voltage of the sliced ​​battery 3 without external force. Current refers to the current intensity when passing through a sliced ​​battery 3, and the magnitude of the current determines the output power of the sliced ​​battery 3. Fill factor refers to the ratio of the maximum power of the sliced ​​battery 3 to the product of its open circuit voltage and short circuit current. Yield rate refers to the percentage of the number of sliced ​​batteries with qualified quality that will appear in the process of passing the test to the number of all sliced ​​batteries tested.

[0094] The performance of the sliced ​​cells 3 after the second laser annealing treatment is tested to check the effects of the two annealing treatments, and qualified sliced ​​cells 3 are screened out. The unqualified sliced ​​cells 3 are subjected to repeated laser annealing treatment to increase the annealing qualified rate of the sliced ​​cells 3. By online testing the appearance, EL, opening voltage, current, filling factor, photoelectric conversion efficiency and yield rate of the manufactured sliced ​​cells 3, the annealing effect can be verified, qualified sliced ​​cells 3 can be screened, and the accuracy of the electrical performance and EL test data of the sliced ​​cells 3 can be ensured.

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

[0096]

[0097] In the above table, the whole cell specifically refers to the solar cell that has not been cut, that is, the finished cell that has not been processed. The difference between the whole cell before laser annealing refers to the performance difference between the sliced ​​cell 3 formed after cutting, which has been passivated on the surface but has not been annealed, and the finished cell. After two laser annealings refers to the performance difference between the sliced ​​cell 3 after the oxide film 32 is plated on the surface, and after the first laser annealing and the second laser annealing, and the finished cell.

[0098] It can be seen from the above table that the above performance difference between the sliced ​​battery 3 after two laser annealings and the whole battery is compared with the difference between the sliced ​​battery before laser annealing and the whole battery. The appearance pass rate and EL pass rate are increased, the current is reduced, the opening voltage is increased, the fill factor is increased, the photoelectric conversion efficiency is increased, and the yield rate is increased, indicating that the overall performance of the sliced ​​battery 3 after two annealing treatments is improved, and the sliced ​​battery 3 is qualified, otherwise it is unqualified and needs to be annealed repeatedly.

[0099] In some embodiments, the sliced ​​battery 3 is first cooled before the performance test is performed on the sliced ​​battery 3. The cooling time is 3.5-5 minutes, and the final temperature of the cooling is 24-26°C.

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

[0101] Before the performance test of the sliced ​​battery 3, if the cooling time is too long, the impact on the sliced ​​battery 3 is not great, but it will extend the working hours. If the cooling temperature is too low, the cooling time will be wasted, which is not conducive to production efficiency. If the cooling time is too short, the sliced ​​battery 3 cannot reach the ideal temperature, which will cause frequent alarms during the sorting of the sliced ​​battery 3, too high temperature, frequent sticking of the slices during sorting, and it is easy for some sliced ​​batteries 3 to be inseparable. In this embodiment, the specific cooling time is 4 minutes, and the final temperature of the cooling process 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 in a direction perpendicular to the battery main grid using a laser cutting method are called two-piece batteries, which have one cutting surface 31. Three identical batteries formed by cutting a standard specification battery in a direction perpendicular to the battery main grid using a laser cutting method are called three-piece batteries, which have two cutting surfaces 31. Similarly, when a standard specification battery is cut in a direction perpendicular to the battery main grid using a laser cutting method to form four, five, etc. identical batteries, they are called four-piece batteries, five-piece batteries, etc., all of which have two cutting surfaces 31, thereby increasing the scope of application of the method.

[0103] In some embodiments, the lasers used in the first laser annealing process and the second laser annealing process are at an angle of 30-60 degrees to the horizontal line.

[0104] The laser is at an angle of 30-60 degrees to the horizontal line, such as 30 degrees, 45 degrees, 60 degrees, etc. In this embodiment, it is 45 degrees, so as to improve the effect of laser annealing. The laser 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 to the horizontal line, avoiding the laser beam from directly irradiating the cutting surface 31, which can make the laser annealing effect more uniform, eliminate the hydroxyl groups and defects generated after the passivation of the cutting surface 31 at the edge of the sliced ​​battery 3, and will not cause damage to the amorphous silicon film layer, and repair the defects in the amorphous silicon film to a certain extent. 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, and the internal temperature of the sliced ​​battery 3 is too high, which may cause the structural damage of the sliced ​​battery 3. If the angle is too small, the internal temperature of the sliced ​​battery 3 may be too low, and the annealing may be uneven.

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

[0106] The annealing method provided in the present application can be applied not only to tunnel oxidation passivation cells, but also to passivation emitter and back local contact cells, and crystalline silicon heterojunction solar cells, and can achieve almost the same effect.

[0107] Comparative Example

[0108] A method for preparing solar cells, which differs from the embodiment in that only one laser annealing treatment is performed. During the laser annealing treatment, a laser beam is used to cover a stack of the cut surfaces 31 of the sliced ​​cells 3 having the passivation layer formed thereon for laser annealing treatment.

[0109] After the laser annealing, the surface structure of the sliced ​​battery 3 in this comparative example was also observed by scanning electron microscope. The SEM image is as follows Figure 5 shown.

[0110] contrast Figure 4 and Figure 5 It can be concluded that from the perspective of the passivation microstructure, the embodiment of the present invention undergoes two laser annealing treatments, and the film layer of the sliced ​​cell 3 after annealing is well maintained, and a complete tunneling layer, polysilicon layer (Poly silicon layer) and oxide film layer (Si x N y The comparative example only performs laser annealing once, and the laser directly irradiates the cut surface 31. After the annealing, the structure of the sliced ​​battery 3 is more seriously damaged. The tunneling layer and polysilicon layer (Poly silicon layer) of the sliced ​​battery 3 are damaged, and the oxide film layer (Si x N y Therefore, the sliced ​​cell preparation method provided by the embodiment of the present invention can eliminate the hydroxyl groups and defects generated by the passivation of the oxidation edge when the cut surface 31 is plated with an oxide film layer, thereby improving the annealing uniformity and the yield rate of photovoltaic modules; and can also avoid directly irradiating the cut surface 31 with laser, which may cause excessive energy to cause the tunneling layer and polysilicon layer (Poly silicon layer) and oxide film layer (Si x N y layer) structure damage without destroying the overall structure of the battery.

[0111] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0112] The above-mentioned embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for a person of ordinary skill in the art, several variations 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 shall be subject to the attached claims.

Claims

1. A method for preparing a sliced ​​battery, characterized in that: The following steps are involved: Provide solar cells; Cutting the solar cell to obtain a plurality of sliced ​​cells (3), wherein the sliced ​​cells (3) have a front side and a back side opposite to each other, and at least one cutting surface (31) connecting the front side and the back side; Performing a passivation treatment on the cut surface (31) of the sliced ​​battery (3) to form a passivation layer on the cut surface (31) of the sliced ​​battery (3); stacking a plurality of the sliced ​​batteries (3) in a manner that the passivation layers of the sliced ​​batteries (3) face the same direction to form a sliced ​​battery stack, wherein a first main surface of the sliced ​​battery stack close to one end of the passivation layer has a first region (2), and a second main surface of the sliced ​​battery stack close to one end of the passivation layer has a second region (7); The sliced ​​battery stack is subjected to laser annealing treatment, wherein the laser annealing treatment comprises: First laser annealing treatment: performing a first laser annealing treatment on the first region (2) of the sliced ​​battery stack; turning over the sliced ​​battery stack; Second laser annealing treatment: performing a second laser annealing treatment on the second region (7) of the sliced ​​battery stack.

2. The preparation method according to 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 preparation method according to claim 1, characterized in that: The laser powers of the first laser annealing treatment and the second laser annealing treatment are the same; Preferably, the laser powers of the first laser annealing treatment and the second laser annealing treatment are both 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 both 275°C-280°C; Preferably, the laser power of the second laser annealing treatment is lower than the laser power of the first laser annealing treatment; Preferably, the laser power of the first laser annealing treatment is 55-68W, and the heating temperature of the first region (2) is 275°C-280°C; the laser power of the second laser annealing treatment is 30-50W, and the heating temperature of the second region (7) is 250°C-255°C.

4. The preparation method according to claim 3, characterized in that: The thickness d of the sliced ​​battery (3) is 120-123 um, and the number of sliced ​​batteries (3) stacked in a stack is 30-50.

5. The preparation method according to claim 1, characterized in that: The method further comprises a step of performing a performance test on the sliced ​​battery (3) after the second laser annealing treatment is completed, and when the performance test finds that the performance of the sliced ​​battery (3) after the second laser annealing treatment is unqualified, repeatedly performing the first laser annealing treatment and the second laser annealing treatment on the unqualified sliced ​​battery (3) until the performance test of the sliced ​​battery (3) is qualified; Preferably, the performance test includes testing at least one of the appearance, EL, opening voltage, current, filling factor, photoelectric conversion efficiency and yield rate of the sliced ​​battery (3).

6. The preparation method according to claim 5, characterized in that: Before the performance test of the sliced ​​battery (3) is carried out, the sliced ​​battery (3) is first subjected to a cooling treatment, the cooling treatment time is 3.5-5 minutes, and the final cooling treatment temperature is 24-26°C.

7. The preparation method according to claim 1, characterized in that: The sliced ​​battery (3) has one cutting surface (31) or two cutting surfaces (31); Preferably, the lasers of the first laser annealing treatment and the second laser annealing treatment form an angle of 30-60 degrees with the horizontal line.

8. The preparation method according to any one of claims 1 to 7, characterized in that: The solar cell is a TOPCon cell, a PERC cell or a HIT cell.

9. A sliced ​​battery, characterized in that: The sliced ​​battery (3) is prepared by the preparation method according to any one of claims 1 to 8.

10. A laser annealing device, used for the laser annealing step in the method for preparing a sliced ​​battery according to any one of claims 1 to 8, characterized in that: The device has a cavity (1), and comprises: A transmission device (4), disposed in the cavity (1), and used for transmitting the sliced ​​battery stack; A laser (5) is disposed in the cavity (1) and is located above the transmission device (4). The laser (5) is tilted and forms an angle of 30-60 degrees with the horizontal line, so that the emitted laser irradiates the first area (2) and / or the second area (7) at an angle of 30-60 degrees.

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