Method for splitting and passivating solar cell, splitting equipment and solar cell

Abstract

A splitting method of a solar cell comprises the steps that the solar cell is provided, the solar cell comprises an upper surface and a lower surface which are opposite to each other, and a scribing direction is set on the upper surface or the lower surface; first laser is adopted for scanning in the scribing direction, and the first laser enables the solar cell to be heated to generate pressure stress; meanwhile, cooling jet flow is sprayed in the scribing direction, the cooling jet flow enables the solar cell to be cooled to generate tensile stress, and along with movement of the first laser and the cooling jet flow, the center of the pressure stress and the center of the tensile stress do not coincide in the horizontal direction perpendicular to the scribing direction, so that the solar cell cracks in the scribing direction to form a fracture surface, and the fracture surface is formed. The section obliquely connects the upper surface and the lower surface. According to the splitting method of the solar cell, the fracture surface obliquely extends, and the method has the advantages of being smaller in roughness, free of raised grains and more thorough in edge isolation. The invention further provides a splitting and passivating method of the solar cell, the solar cell and splitting equipment.

Description

Technical Field

[0001] The present application relates to the field of photovoltaic material manufacturing and processing, and more specifically, to a method for splitting a solar cell, a method for splitting and passivating a solar cell, a splitting device, and a solar cell obtained by the splitting and passivation method. Background Art

[0002] In the current mainstream photovoltaic cell preparation process, photovoltaic cells are usually divided into half slices or even multiple slices to reduce the internal resistance and current loss after series connection, thereby reducing temperature loss and shading loss and improving packaging efficiency. At present, the splitting method of photovoltaic cells usually uses lasers, mainly including laser melting splitting and laser non-destructive splitting. Laser melting splitting uses laser to ablate the required position on the surface of the photovoltaic cell to form continuous lines, and then assists with mechanical splitting to form sub-cells. Laser non-destructive splitting only requires a very short initial laser line to guide the starting crack, and stress is formed by the thermal cracking laser and the subsequent cooling jet to split the cell. Laser non-destructive splitting has the advantages of smooth cross-section, small heat-affected zone, low sub-cell efficiency loss, and no bending strength attenuation, and is widely used in high-efficiency crystalline silicon solar cells and modules. However, the new cross-section produced by laser non-destructive splitting still has the disadvantage of causing edge recombination of carriers, resulting in power loss. Summary of the invention

[0003] In view of this, the present application provides a method for splitting a solar cell, comprising:

[0004] Providing a solar cell sheet, the solar cell sheet comprising an upper surface and a lower surface opposite to each other, and setting a scribing direction on the upper surface and / or the lower surface;

[0005] The solar cell is scanned along the scribing direction by a first laser, the first laser heats the solar cell to generate compressive stress; and a cooling jet is sprayed along the scribing direction by a cooling jet to cool the solar cell to generate tensile stress;

[0006] Among them, as the first laser and the cooling jet move, the center of the compressive stress and the center of the tensile stress always do not overlap in a horizontal direction perpendicular to the scribing direction, so that the solar cell is cracked along the scribing direction to form a cross-section, the cross-section is obliquely connected to the upper surface and the lower surface, and the horizontal direction is parallel to the upper surface and / or the lower surface.

[0007] The solar cell segmentation method of the present application is a lossless segmentation method. By setting asymmetric compressive stress and tensile stress at the center, oblique shear stress is formed inside the solar cell to guide the cross section of the solar cell to extend obliquely. While having the advantages of conventional lossless slicing, such as flat cross section, small heat-affected zone, low sub-cell efficiency loss, and no bending strength attenuation, the inclined cross section is less affected by stress deviation disturbance, has good cross section guidance, and has improved straightness and cross section flatness, less roughness, and no ripples, corresponding to better cross section quality. The subsequent application of edge passivation technology has a good passivation effect, thereby effectively reducing the edge recombination of carriers.

[0008] In some embodiments, the first laser is a continuous laser with a wavelength of 300-1200 nm, a spot impact area width of 100-2000 μm, and a power density of 1×10 3 -1×10 5 W / cm 2 .

[0009] In some embodiments, the cooling jet is a water flow, an air flow, or an atomized water flow.

[0010] In some embodiments, the method for splitting a solar cell further comprises: before scanning the solar cell with the first laser, using a second laser to create cuts at both ends of the solar cell along the slicing direction; or,

[0011] The method for splitting a solar cell also includes: before using the first laser to scan the solar cell, using a second laser to open an incision at one end of the solar cell along the scribing direction; while the first laser is scanning the solar cell, continuing to use the second laser to open an incision at the other end of the solar cell along the scribing direction.

[0012] In some embodiments, the width of the incision is 10-30 μm, the length is 0.1-2 mm, the depth is 10%-50% of the thickness of the solar cell, the length of the incision is parallel to the scribing direction, and the width is perpendicular to the scribing direction; the second laser is a pulsed laser with a wavelength of 300-1200 nm and a pulse width of 10 -11 -10 -7 s, spot size is 10-30μm, energy density is 30-200J / cm 2 ; Both the first laser and the second laser are implemented on the upper surface of the solar cell.

[0013] In some embodiments, an acute angle θ is formed between the cross section and the upper surface or the lower surface, and 45°≦θ<90°.

[0014] The present application also provides a splitting device used in the above splitting method, including:

[0015] A cell carrier, used to carry solar cells;

[0016] A thermal cracking laser head, which is arranged above or below the battery cell carrier and is used to emit a first laser;

[0017] A slotting laser head, which is disposed above or below the cell carrier and is used to emit a second laser;

[0018] A cooling unit, which is disposed above or below the cell carrier and is used to spray a cooling jet;

[0019] The first laser of the thermal splitting laser head and the cooling jet of the cooling part do not overlap in a horizontal direction perpendicular to the scribing direction.

[0020] In some embodiments, the slotting laser head, the thermal cracking laser head, and the cooling unit are sequentially arranged along the scribing direction;

[0021] Along the scribing direction, the grooving laser head, the thermal cracking laser head, and the cooling unit are slidably arranged relative to the cell carrier;

[0022] The thermal splitting laser head and the cooling part are movably arranged along a horizontal direction perpendicular to the scribing direction.

[0023] The present application also provides a method for splitting and passivating a solar cell, comprising:

[0024] Providing a solar cell sheet, the solar cell sheet comprising an upper surface and a lower surface opposite to each other, and setting a scribing position and a scribing direction on the upper surface and / or the lower surface;

[0025] The solar cell is scanned along the scribing direction by a first laser, the first laser heats the solar cell to generate compressive stress; and a cooling jet is sprayed along the scribing direction by a cooling jet to cool the solar cell to generate tensile stress;

[0026] Wherein, as the first laser and the cooling jet move, the center of the compressive stress and the center of the tensile stress always do not overlap in a horizontal direction perpendicular to the scribing direction, so that the solar cell is cracked along the scribing direction to form a cross section, and the cross section obliquely connects the upper surface and the lower surface;

[0027] A passivation layer is formed on the cross section.

[0028] Compared with vertical sections, inclined sections have the following advantages in passivation: (1) Reduced surface recombination: The inclined section can effectively reduce surface recombination through a more uniform passivation layer coverage. This means that more electrons can participate in the conduction of photocurrent, improving the open circuit voltage (Voc) and fill factor (pFF) of the battery. (2) Improved battery stability: A more uniform passivation layer and reduced stress concentration make the battery more stable during long-term use, reduce cracks and damage caused by stress, and improve the reliability and service life of the battery. (3) Process compatibility: The design of the inclined section can better adapt to different passivation processes, such as plasma enhanced chemical vapor deposition (PECVD) and atomic layer deposition (ALD), allowing these processes to achieve more efficient passivation effects on inclined surfaces. (4) Facilitate uniform deposition of passivation materials: The inclined section provides a larger surface area, which is conducive to the uniform deposition of passivation materials. This can reduce defects in the passivation layer and ensure consistent passivation effects across the entire section.

[0029] In some embodiments, the passivation layer is a silicon oxide layer with a thickness of 1-4 nm induced by treating the cross section with laser irradiation.

[0030] In some embodiments, the laser irradiating the cross section is an ultraviolet pulse laser with a wavelength of 266-365 nm and a pulse width of 10 -13 -10 -11 s, spot size is 50-300μm, energy density is 50-1000mJ / cm 2 .

[0031] In some embodiments, the passivation layer is an aluminum oxide film with a thickness of 3-50 nm formed by atomic layer deposition.

[0032] The present application also provides a solar cell, comprising: an upper surface and a lower surface opposite to each other, and a side surface connected between the upper surface and the lower surface, wherein at least one of the side surfaces is obliquely connected to the upper surface and the lower surface, and the side surface is covered with a passivation layer.

[0033] In some embodiments, an acute angle θ is formed between the side covered with the passivation layer and the upper surface or the lower surface, 45°≦θ<90°; the passivation layer is a silicon oxide layer with a thickness of 1-4nm or an aluminum oxide film with a thickness of 3-50nm. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 FIG. 1 is a schematic diagram of a method for splitting a solar cell according to an embodiment of the present application.

[0035] Figure 2 FIG. 1 is a cross-sectional schematic diagram of a method for splitting a solar cell according to an embodiment of the present application.

[0036] Figure 3 Schematic diagram of cutting a solar cell into two parts.

[0037] Figure 4 Schematic diagram of the module of the wafer splitting equipment used for solar cells.

[0038] Description of main component symbols:

[0039] 100, solar cell; 101, first heat-affected zone; 102, second heat-affected zone; 10, first laser; 20, cooling jet; 11, upper surface; 12, lower surface; 13, cross section; 15, scribing direction; 17, incision; 200, slicing equipment; 210, slotting laser head; 220, thermal cracking laser head; 230, cooling unit; 240, cell carrier. DETAILED DESCRIPTION

[0040] The present application provides a method for splitting a solar cell. By setting a thermal stress with non-overlapping centers, the solar cell is broken, and the formed cross-section extends obliquely (not parallel to the thickness direction of the solar cell, or not perpendicular to the upper surface or lower surface of the solar cell), thereby having a better edge separation effect and lower edge recombination. Moreover, due to the smoothness and larger area of ​​the newly generated cross-section, after applying the edge passivation technology, the electrical performance parameters are greatly improved and the conversion efficiency is higher, thereby achieving an increase in the power of the photovoltaic module.

[0041] See also Figure 1 and Figure 2 The method for splitting the solar cell 100 includes:

[0042] A solar cell 100 to be split is provided, wherein the solar cell 100 comprises an upper surface 11 and a lower surface 12 opposite to each other, and a slicing position and a slicing direction 15 are set on the upper surface 11 and / or the lower surface 12;

[0043] Scanning the solar cell 100 at a scribing position and along a scribing direction 15 with a first laser 10, the first laser 10 heats the solar cell 100 to generate expansion compressive stress; and

[0044] At the same time, a cooling jet 20 is used to spray the solar cell 100 at the scribing position and along the scribing direction 15. The cooling jet 20 causes the solar cell 100 to be cooled to generate tensile stress of contraction. As the first laser 10 and the cooling jet 20 move, the center of the compressive stress and the center of the tensile stress do not overlap along the horizontal direction perpendicular to the scribing direction 15. The horizontal direction described in the present application refers to a direction parallel to the upper surface 11 and / or the lower surface 12.

[0045] The solar cell 100 is generally in the shape of a rectangular plate, and the scribing direction 15 is parallel to one of the outer edges of the solar cell 100 , such as the outer edge in the length direction or the outer edge in the width direction.

[0046] The same area of ​​the solar cell 100 is first irradiated with the first laser 10 and then sprayed with the cooling jet 20 , in a sequential order. In some embodiments, along the scribing direction 15 , the first laser 10 and the cooling jet 20 are moved one after the other, and the cooling jet 20 closely follows the first laser 10 .

[0047] Under the action of asymmetric compressive stress and tensile stress, oblique shear stress is formed inside the solar cell 100, causing it to crack along the dicing direction 15, and the cross section 13 is not perpendicular to the upper surface 11 and the lower surface 12, that is, the cross section 13 is obliquely connected to the upper surface 11 and the lower surface 12. In the embodiment of the present application, the dicing position and dicing direction 15 are set on the upper surface 11.

[0048] The existing splitting method usually overlaps the center of compressive stress and the center of tensile stress in the horizontal direction perpendicular to the slicing direction 15, thereby obtaining thermal stress parallel to the thickness direction of the solar cell 100. The thermal stress causes the solar cell 100 to break internally to form a cross section parallel to the thickness direction of the solar cell 100.

[0049] In the present application, the center of the compressive stress of the solar cell 100 and the center of the tensile stress are set not to overlap in the horizontal direction perpendicular to the slicing direction 15, thereby forming an inclined shear stress (not parallel to the thickness direction of the solar cell 100) inside the solar cell 100, and the shear stress causes the inside of the solar cell 100 to break along the slicing direction 15 to form an inclined cross section 13, the cross section 13 intersects with the thickness direction of the solar cell 100, and the cross section 13 obliquely connects the upper surface 11 and the lower surface 12. The inclined cross section 13 is less affected by the stress deviation disturbance, has good cross section guidance, and has improved straightness and cross section flatness, less roughness, no ripples, corresponding to better cross section quality, and good passivation effect of the subsequent edge passivation technology. In short, compared with the cross section perpendicular to the upper and lower surfaces, the inclined cross section has a larger exposed area and better cross section quality, and the cell formed after the split has a small cut loss.

[0050] The first laser 10 causes local instantaneous temperature rise of the solar cell 100, generating compressive stress in the solar cell 100. The cooling jet causes local temperature drop of the solar cell 100, generating tensile stress in the solar cell 100. The compressive stress and tensile stress cooperate to cause the solar cell 100 to crack, without the need for mechanical breaking.

[0051] In some embodiments, the first laser 10 is a continuous laser with a wavelength of 300-1200 nm, a spot impact area width of 100-2000 μm, and a power density of 1×10 3 -1×10 5 W / cm 2 . For example, the wavelength of the first laser 10 may be 355nm, 365nm, 405nm, 515nm, 532nm, 540nm, 660nm, 1064nm, 1080nm, etc. The width of the spot influence area of ​​the first laser 10 may be 100μm, 200μm, 300μm, 400μm, 500μm, 600μm, 700μm, 800μm, 900μm, 1000μm, 1100μm, 1200μm, 1300μm, 1400μm, 1500μm, 1600μm, 1700μm, 1800μm, 1900μm, 2000μm. The present application sets a certain width of the spot influence area to ensure that the first laser 10 can crack the solar cell 100. If the width of the spot influence area is too wide or too narrow, the cell will not be cracked. The power density of the first laser 10 is 1×10 3 W / cm 2 , 3×10 3 W / cm 2 , 5×10 3 W / cm 2 ,7×10 3 W / cm 2 ,9×10 3 W / cm 2 , 1×10 4 W / cm 2 , 3×10 4 W / cm 2 , 5×10 4 W / cm 2 ,7×10 4 W / cm 2 ,9×10 4 W / cm 2 , 1×10 5 W / cm 2 The high energy power density of the first laser 10 can cause the solar cell 100 to be locally and instantaneously heated after being irradiated, so as to generate a sufficient temperature difference.

[0052] In some embodiments, the cooling jet 20 is used to locally cool the solar cell 100 and may be water flow, air flow, or atomized water flow (containing both water and gas), but is not limited thereto and may also be other cooling jets conventionally used in the art.

[0053] In one embodiment, please continue to refer to Figure 1, the first laser 10 directly irradiates the surface of the solar cell 100 to form a first heat-affected zone 101, and the length and width of the first heat-affected zone 101 are related to the spot setting of the first laser 10 (such as spot size, defocus, etc.). Since the first laser 10 will scan along the direction of the scribing direction 15, the position of the first heat-affected zone 101 will also move along the direction of the scribing direction 15. The cooling jet 20 directly sprays the surface of the solar cell 100 to form a second heat-affected zone 102, and the position of the second heat-affected zone 102 will also move along the scribing direction 15. In the embodiment of the present application, the first heat-affected zone 101 can be circular, elliptical or rectangular, but is not limited thereto.

[0054] Combined with reference Figure 1 and Figure 2 The center of the first heat-affected zone 101 may be a stress concentration position of compressive stress, and the center of compressive stress radiates compressive stress to all directions in the solar cell 100. As the first laser 10 moves along the scribing direction 15, the center of compressive stress also moves along the scribing direction 15. The center of the second heat-affected zone 102 may be a stress concentration position of tensile stress, and the center of tensile stress radiates tensile stress to all directions in the solar cell 100. As the cooling jet 20 moves along the scribing direction 15, the center of tensile stress also moves along the scribing direction 15. Figure 2 As shown, the direction of the compressive stress is from the center to the outside, and the direction of the tensile stress is from the outside to the center. As the first laser 10 and the cooling jet 20 both move along the scribing direction 15, the center of the first heat-affected zone 101 and the center of the second heat-affected zone 102 do not overlap along the horizontal direction perpendicular to the scribing direction 15, and the center of the compressive stress and the center of the tensile stress do not overlap along the horizontal direction perpendicular to the scribing direction 15.

[0055] In the embodiment of the present application, the moving path of the first laser 10 and the moving path of the cooling jet 20 are both parallel to the scribing direction 15 .

[0056] Figure 1 and Figure 2 As shown, along the vertical scribing direction 15 , the center of the first heat-affected zone 101 and the center of the second heat-affected zone 102 are obviously spaced apart (not overlapping). Figure 1 In the figure, the first heat affected zone 101 and the second heat affected zone 102 do not overlap. In actual operation, the first heat affected zone 101 and the second heat affected zone 102 may partially overlap, as long as the center of the first heat affected zone 101 and the center of the second heat affected zone 102 do not overlap in the horizontal direction perpendicular to the dicing direction 15. Figure 1 In the figure, the first heat affected zone 101 is an ellipse, and the second heat affected zone 102 is a circle, which are presented as schematic diagrams and are not limited thereto. The specific shapes can be adjusted according to the settings of the laser.

[0057] In the horizontal direction perpendicular to the slicing direction 15, under the combined effect of the non-coincident compressive stress and the tensile stress (two thermal stresses), an oblique shear stress is formed inside the solar cell 100, so that the solar cell 100 is broken and split into two parts along the slicing direction 15, and each split part has a newly generated cross section 13, such as Figure 3 As shown, the section 13 obliquely connects (non-perpendicularly) the upper surface 11 and the lower surface 12 , and a non-90 degree angle is formed between the section 13 and the upper surface 11 or the lower surface 12 of the solar cell 100 .

[0058] The first laser 10 scans along the scribing direction 15 while the solar cell 100 remains stationary and the first laser 10 is moved, or the first laser 10 remains stationary and the solar cell 100 is moved. The cooling jet 20 sprays along the scribing direction 15 while the solar cell 100 remains stationary and the cooling jet 20 is moved, or the cooling jet 20 remains stationary and the solar cell 100 is moved.

[0059] In some embodiments, the method for splitting the solar cell 100 further includes: before scanning the solar cell 100 with the first laser 10, using the second laser to open incisions 17 (such as Figure 1 As shown in the figure, the second laser 10 is used to guide the direction of the splitting, so that the solar cell 100 can be split faster and better when the first laser 10 is used for irradiation. For example, in actual operation, the second laser 10 and the first laser 10 move relative to the solar cell 100 one after the other, the second laser is in front to form the incision 17 first to guide the direction of the splitting, and the first laser 10 is in the back to split the solar cell 100.

[0060] The preset cutout 17 can well guide the initial splitting direction of the solar cell 100, so that the solar cell 100 is split along the slicing direction 15, ensuring the straightness of the splitting.

[0061] In some embodiments, the method for splitting a solar cell 100 further includes: before using the first laser 10 to scan the solar cell 100, using the second laser to open an incision 17 at one end of the solar cell 100 along the scribing direction 15; using the first laser 10 to start scanning from the incision 17 of the solar cell 100, and simultaneously using the second laser to open an incision 17 at the other end of the solar cell 100 along the scribing direction 15.

[0062] In some embodiments, the width of the cut 17 is 10-30 μm, the length is 0.1-2 mm, and the depth is 10%-50% of the thickness of the solar cell 100. The length of the cut 17 is parallel to the scribing direction 15, and the width is perpendicular to the scribing direction 15. By reasonably setting the length and depth of the cut 17, it is ensured that the cut 17 can play a role in guiding the direction of the solar cell 100 to split. If the length of the cut 17 is too short, for example, less than 0.1 mm, and the depth of the cut 17 is too shallow, less than 10% of the thickness of the solar cell 100, the role of the cut 17 in guiding the direction of the split is weak. If the length of the cut 17 is too long, for example, more than 2 mm, and the depth is too deep, more than 10%-50% of the thickness of the solar cell 100, the power consumption and action time required by the second laser may need to be increased, resulting in a corresponding increase in the cost and time of the splitting method, which is not conducive to cost reduction and efficiency improvement.

[0063] The second laser is a pulse laser with a wavelength of 300-1200nm and a pulse width of 10 -11 -10 -7 s, spot diameter is 10-30μm, energy density is 30-200J / cm 2 For example, the wavelength of the second laser may be 300nm, 350nm, 400nm, 450nm, 500nm, 550nm, 600nm, 650nm, 700nm, 750nm, 800nm, 850nm, 900nm, 950nm, 1000nm, 1050nm, 1100nm, 1150nm, 1200nm, and the pulse width may be 10 -11 s, 10 -10 s, 10 -9 s, 10 -8 s, 10 -7 s, the spot diameter can be 15μm, 17μm, 19μm, 20μm, 20μm, 21μm, 23μm, 25μm, 27μm, 29μm, 30μm, and the energy density can be 30J / cm 2 , 50J / cm 2 、80J / cm 2 、100J / cm 2 , 120J / cm 2 、130J / cm 2 、150J / cm 2 、160J / cm 2 、170J / cm 2 、180J / cm 2 、190J / cm 2 , 200J / cm 2By reasonably setting the parameters of the second laser such as pulse width, spot diameter, energy density, etc., the second laser can quickly form a required incision 17 of a certain size in the solar cell 100 .

[0064] In some embodiments, preferably, the second laser and the first laser 10 coincide with each other in the scribing direction 15 .

[0065] The solar cell 100 includes an upper surface 11 and a lower surface 12 opposite to each other, the first laser 10 can act on the upper surface 11 or the lower surface 12, the second laser can act on the upper surface 11 or the lower surface 12, and the cooling jet 20 can act on the upper surface 11 or the lower surface 12. The first laser 10, the second laser and the cooling jet 20 can be located on the same surface or different surfaces of the solar cell 100.

[0066] In some embodiments, for TOPCon cells, both the first laser 10 and the second laser act on the upper surface 11 of the solar cell 100 to reduce cutting loss and leakage.

[0067] The present application also provides a method for splitting and passivating a solar cell 100 , including the aforementioned splitting method, and further comprising: forming a passivation layer on the cross section 13 of the solar cell to passivate the cross section 13 .

[0068] Compared with vertical sections, inclined sections have the following advantages in passivation:

[0069] (1) Reduce surface recombination: The inclined section can effectively reduce surface recombination through more uniform passivation layer coverage, which means that more electrons can participate in the conduction of photocurrent and improve the open circuit voltage (Voc) and fill factor (pFF) of the battery.

[0070] (2) Improved battery stability: A more uniform passivation layer and reduced stress concentration make the battery cell more stable during long-term use, reduce cracks and damage caused by stress, and improve battery reliability and service life.

[0071] (3) Process compatibility: The design of the inclined cross-section can better adapt to different passivation processes, such as plasma enhanced chemical vapor deposition (PECVD) and atomic layer deposition (ALD), enabling these processes to achieve more efficient passivation effects on inclined surfaces.

[0072] (4) Facilitates uniform deposition of passivation materials: The inclined section provides a larger surface area, which is conducive to the uniform deposition of passivation materials. This can reduce defects in the passivation layer and ensure consistent passivation effects across the entire section.

[0073] In some embodiments, the passivation layer is a silicon oxide layer induced by laser. The solar cell is usually a silicon wafer, and laser irradiation is used to induce oxidation of the silicon wafer to form a silicon oxide layer. The laser can irradiate the section 13 vertically or obliquely. The vertical irradiation of the section 13 is more effective and can ensure that the passivation layer is formed uniformly. Specifically, the solar cell wafer cells after the splitting are stacked up and down, and the section 13 is exposed and located on the same side of the stack. The exposed section 13 is treated by laser irradiation to induce the formation of a silicon oxide layer, and the thickness of the silicon oxide layer is 1-4nm.

[0074] In some embodiments, the laser for inducing oxidation is an ultraviolet pulse laser with a wavelength of 266-365 nm and a pulse width of 10 -13 -10 - 11 s, spot size 50-300μm, energy density 50-1000mJ / cm 2 By setting the parameters of the induction laser, it is ensured that after the cross section 13 is irradiated by the oxidation-inducing laser, the exposed silicon on the cross section 13 can be oxidized to form a uniform silicon oxide layer.

[0075] The laser-induced passivation solution of forming a silicon oxide layer has the advantages of low cost and high productivity. Combined with the edge passivation process, it may produce higher cell efficiency and component power gain.

[0076] In some embodiments, the passivation layer is an aluminum oxide film with a thickness of 3-50 nm deposited on the cross section 13 by atomic layer deposition. The formation of the aluminum oxide film includes: placing the solar cell with the exposed cross section into an atomic layer deposition device, introducing reactants and carrier gas into the atomic layer deposition device, reacting to form an aluminum oxide film on the cross section. In some embodiments, the reactants include trimethylaluminum (TMA) and water, and nitrogen can be used as the carrier gas. The Al2O3 material formed by this method has a surface area of ​​up to 10 12 -10 13 cm -2 The fixed negative charge of the charge density can effectively realize field effect passivation, and the high hydrogen content of the reactant TMA can be used to reduce the surface defect density, thereby obtaining an excellent edge passivation effect. Furthermore, after the atomic layer deposition of the aluminum oxide film, it is necessary to anneal at 220-270°C (for example, 250°C), and the annealing treatment can improve the passivation effect of the aluminum oxide film.

[0077] The passivation process of forming an aluminum oxide film on an inclined cross section by atomic layer deposition has the following advantages:

[0078] (1) Reducing surface defects: The inclined cross-section formed by laser cleavage can reduce mechanical and thermal stress concentration, thereby reducing the risk of surface defects and cracks when depositing aluminum oxide films, thereby improving the quality and consistency of the film.

[0079] (2) Enhance film adhesion: The inclined section provides a larger surface area, which is conducive to the adhesion of the aluminum oxide film. Good adhesion helps to improve the stability and durability of the passivation layer and prevent the film from falling off during subsequent processing or use.

[0080] (3) Excellent surface passivation effect: The uniformly covered aluminum oxide film can significantly reduce the surface recombination rate, increase the open circuit voltage (Voc) and fill factor (pFF) of the battery, and thus improve the photoelectric conversion efficiency of the photovoltaic cell.

[0081] (4) Reducing interface defects: The aluminum oxide film formed on the inclined cross section by atomic layer deposition has a dense film layer, which can reduce interface defects and trap state density, which helps to improve the carrier lifetime and transmission efficiency of the battery and further improve battery performance.

[0082] (5) Improve battery stability and durability: Uniform and high-quality aluminum oxide film has good chemical and mechanical stability, which can protect the battery surface from erosion by environmental factors (such as moisture and oxygen) and extend the battery life.

[0083] (6) Improved current conduction: Uniformly passivated surface reduces edge recombination and leakage current.

[0084] like Figure 3 As shown, the cross section 13 of the solar cell 100 is a newly formed surface by the above-mentioned splitting method. The solar cell 100 includes a parallel and opposite upper surface 11 and a lower surface 12. The solar cell 100 generally includes two side surfaces connected between the upper surface 11 and the lower surface 12, and at least one of the two side surfaces is a cross section 13. The cross section 13 is connected between the upper surface 11 and the lower surface 12, and is a side surface of the solar cell obtained by the splitting method. Different from the conventional non-destructive slicing cross section arranged perpendicular to the upper surface 11 and the lower surface 12, the cross section 13 formed in the present application extends obliquely and is not perpendicularly connected to the upper surface 11 and the lower surface 12. Compared with the cross section perpendicular to the upper surface 11 and the lower surface 12, the cross section 13 extending obliquely in the present application is larger and smoother.

[0085] In some embodiments, Figure 3As shown, the upper surface 11 and the lower surface 12 are perpendicular to the thickness direction of the solar cell 100, and the acute angle between the cross section 13 and the upper surface 11 or the lower surface 12 of the solar cell 100 is θ, 45°≦θ<90°. For example, the angle between the cross section 13 and the upper surface 11 or the lower surface 12 is 65°-70°, for example, the angle between the cross section 13 and the upper surface 11 or the lower surface 12 is 45°-65°. The angle between the cross section 13 and one of the upper surface 11 and the lower surface 12 is an acute angle, and the angle between the cross section 13 and the other of the upper surface 11 and the lower surface 12 is an obtuse angle.

[0086] In some embodiments, the cross section 13 is covered with a passivation layer (not shown). The passivation layer may be a silicon oxide layer with a thickness of 1-4 nm formed by laser induction or an aluminum oxide film with a thickness of 3-50 nm formed by deposition.

[0087] Furthermore, the characteristics of the cross section 13 include but are not limited to being flat and smooth without slag, having almost no heat-affected zone except for the head and tail cut positions, and having little loss in slicing efficiency.

[0088] The inclined section also has many advantages over the vertical section. The inclined section has less roughness, better guidance, improved straightness and section flatness, and no ripples, that is, the surface quality of the section is better, and the passivation effect achieved by the corresponding section edge passivation process is good. The edge isolation of the inclined section is more thorough, the cell formed after the split has less cutting loss and less leakage. Under the same cutting loss (the photovoltaic cell conversion efficiency is reduced due to slicing), there is lower carrier edge recombination. The larger exposed area of ​​the inclined section leads to a greater improvement in electrical performance and conversion efficiency after the edge passivation process.

[0089] See also Figure 4 The present application also provides a cleaving device 200 for the cleaving method of the solar cell of the present application. The cleaving device 200 includes a slotting laser head 210, a thermal cleaving laser head 220, a cooling unit 230 and a cell carrier 240.

[0090] The cell carrier 240 is used to carry the solar cell. The thermal cracking laser head 220 includes a continuous laser and a lens group connected thereto, and is used to emit a first laser. The slotting laser head 210 includes a pulsed laser and a lens group connected thereto, and the slotting laser head 210 is used to emit a second laser. The light spots of the first laser and the second laser are circular, elliptical, or long strips. The cooling unit 230 is connected to an air source and a water source to spray a cooling flow.

[0091] The slotting laser head 210, the thermal splitting laser head 220, and the cooling unit 230 are respectively arranged opposite to the cell carrier 240 and are separated by a distance. The slotting laser head 210, the thermal splitting laser head 220, and the cooling unit 230 can be located on the same side or different sides of the cell carrier 240, that is, the slotting laser head 210, the thermal splitting laser head 220, and the cooling unit 230 can be arranged above and / or below the cell carrier 240. Preferably, the slotting laser head 210 and the thermal splitting laser head 220 are both located above the cell carrier 240, so that the first laser and the second laser are implemented on the front surface of the solar cell, thereby reducing the cutting loss of the solar cell (such as the TOPCon cell) and reducing leakage.

[0092] To ensure that the center of tensile stress of the cooling jet acting on the cell carrier 240 and the center of compressive stress of the first laser acting on the cell carrier 240 do not overlap in the horizontal direction perpendicular to the scribing direction 15, the first laser of the thermal splitting laser head 210 and the cooling jet of the cooling unit 230 are set to not overlap in the horizontal direction perpendicular to the scribing direction. For example, the position of the thermal splitting laser head 210 and the cooling unit 230 can be finely adjusted in the vertical scribing direction, that is, movable.

[0093] In some embodiments, the grooving laser head 210 , the thermal splitting laser head 220 , and the cooling unit 230 are slidably arranged relative to the cell carrier 240 , so that the grooving laser head 210 , the thermal splitting laser head 220 , and the cooling unit 230 can move along the scribing direction 15 .

[0094] The slotting laser head 210, the thermal cracking laser head 220, and the cooling unit 230 are sequentially arranged along the scribing direction 15. Specifically, the cuts 17 at both ends of the scribing direction 15 are sequentially acted upon by the second laser, the first laser, and the cooling jet, and the non-cut positions in the scribing area are sequentially acted upon by the first laser and the cooling jet. The specific implementation method includes but is not limited to the sequential arrangement of the positions and / or the sequential arrangement of the opening times.

[0095] The solar cell splitting method of the present application is a non-destructive splitting method. By setting asymmetric compressive stress and tensile stress in the slicing direction, oblique shear stress is formed inside the solar cell, guiding the cross section of the solar cell to extend obliquely. While having the advantages of flat cross section, small heat-affected zone, low sub-cell efficiency loss, and no bending strength attenuation, the inclined cross section is less affected by stress deviation disturbance, has good cross-section guidance, and has improved straightness and cross-section flatness, less roughness, and no ripples, corresponding to better cross-section quality, and the subsequent passivation effect of edge passivation technology is good.

[0096] The oblique cross section in this application has a larger exposed area and better cross section quality, and the cell formed after splitting has a small cut loss. After passivation process treatment, edge recombination and leakage can be significantly reduced. Therefore, the inclined cross section has a better edge separation effect and lower edge recombination, which can effectively improve the open circuit voltage (Voc) and fill factor (pFF) of the cell, improve the battery electrical performance, component reliability and photoelectric conversion efficiency. The lossless splitting method of solar cells with optimized cross section combined with the edge passivation process can obtain an additional 0-0.1% abs improvement in cell conversion efficiency and 3-5W increase in component power, which is conducive to cost reduction and efficiency improvement.

[0097] The above implementation modes are only used to illustrate the technical solutions of the present application and are not intended to limit the present application. Although the present application has been described in detail with reference to the above preferred implementation modes, a person skilled in the art should understand that the technical solutions of the present application may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present application.

Claims

1. A method for splitting a solar cell, characterized in that: include: Providing a solar cell sheet, the solar cell sheet comprising an upper surface and a lower surface opposite to each other, and setting a scribing direction on the upper surface and / or the lower surface; The solar cell is scanned along the scribing direction by a first laser, the first laser heats the solar cell to generate compressive stress; and a cooling jet is sprayed along the scribing direction by a cooling jet to cool the solar cell to generate tensile stress; Among them, as the first laser and the cooling jet move, the center of the compressive stress and the center of the tensile stress always do not overlap in a horizontal direction perpendicular to the scribing direction, so that the solar cell is cracked along the scribing direction to form a cross-section, the cross-section is obliquely connected to the upper surface and the lower surface, and the horizontal direction is a direction parallel to the upper surface and / or the lower surface.

2. The method for splitting a solar cell according to claim 1, characterized in that: The first laser is a continuous laser with a wavelength of 300-1200nm, a spot impact area width of 100-2000μm, and a power density of 1×10 3 -1×10 5 W / cm 2 .

3. The method for splitting a solar cell according to claim 1, characterized in that: The cooling jet is water flow, or air flow, or atomized water flow.

4. The method for splitting a solar cell according to claim 1, characterized in that: The method for splitting a solar cell also includes: before using the first laser to scan the solar cell, using a second laser to create cuts at both ends of the solar cell along the slicing direction; or, The method for splitting a solar cell also includes: before using the first laser to scan the solar cell, using a second laser to open an incision at one end of the solar cell along the scribing direction; while the first laser is scanning the solar cell, continuing to use the second laser to open an incision at the other end of the solar cell along the scribing direction.

5. The method for splitting a solar cell according to claim 4, characterized in that: The width of the cut is 10-30 μm, the length is 0.1-2 mm, and the depth is 10%-50% of the thickness of the solar cell. The length of the cut is parallel to the scribing direction, and the width is perpendicular to the scribing direction. The second laser is a pulsed laser with a wavelength of 300-1200nm and a pulse width of 10 -11 -10 -7 s, spot size is 10-30μm, energy density is 30-200J / cm 2 ; The first laser and the second laser are both applied on the upper surface of the solar cell.

6. The method for splitting a solar cell according to claim 1, characterized in that: An acute angle θ is formed between the cross section and the upper surface or the lower surface, and 45°≦θ<90°.

7. A chip splitting device used in the chip splitting method according to claim 1, characterized in that: The splitting device comprises: A cell carrier, used to carry solar cells; A thermal cracking laser head, which is arranged above or below the battery cell carrier and is used to emit a first laser; A slotting laser head, which is disposed above or below the cell carrier and is used to emit a second laser; A cooling unit, which is disposed above or below the cell carrier and is used to spray a cooling jet; The first laser of the thermal splitting laser head and the cooling jet of the cooling part do not overlap in a horizontal direction perpendicular to the scribing direction.

8. The splitting device according to claim 7, characterized in that: The slotting laser head, the thermal cracking laser head, and the cooling unit are sequentially arranged along the scribing direction; Along the scribing direction, the grooving laser head, the thermal cracking laser head, and the cooling unit are all slidably arranged with the cell carrier; The thermal splitting laser head and the cooling part are movably arranged along a direction perpendicular to the scribing direction.

9. A method for splitting and passivating a solar cell, characterized in that: include: Providing a solar cell sheet, the solar cell sheet comprising an upper surface and a lower surface opposite to each other, and setting a scribing direction on the upper surface and / or the lower surface; Scanning the solar cell along the scribing direction using a first laser, wherein the first laser heats the solar cell to generate compressive stress; At the same time, a cooling jet is used to spray the solar cell along the dicing direction, and the cooling jet causes the solar cell to be cooled to generate tensile stress; Wherein, as the first laser and the cooling jet move, the center of the compressive stress and the center of the tensile stress always do not overlap in a horizontal direction perpendicular to the scribing direction, so that the solar cell is cracked along the scribing direction to form a cross section, the cross section obliquely connects the upper surface and the lower surface, and the horizontal direction is a direction parallel to the upper surface and / or the lower surface; A passivation layer is formed on the cross section.

10. The method for splitting and passivating a solar cell according to claim 9, characterized in that: The passivation layer is a silicon oxide layer with a thickness of 1-4 nm induced by treating the cross section with laser irradiation; The laser irradiating the cross section is an ultraviolet pulse laser with a wavelength of 266-365nm and a pulse width of 10 -13 -10 -11 s, spot size is 50-300μm, energy density is 50-1000mJ / cm 2 ;or The passivation layer is an aluminum oxide film with a thickness of 3-50 nm formed by atomic layer deposition.

11. A solar cell, characterized in that: include: An upper surface and a lower surface are opposite to each other, and a side surface is connected between the upper surface and the lower surface, wherein at least one of the side surfaces is connected obliquely to the upper surface and the lower surface, and the side surface is covered with a passivation layer.

12. The solar cell according to claim 11, characterized in that: An acute angle θ is formed between the side surface covered with the passivation layer and the upper surface or the lower surface, 45°≦θ<90°; the passivation layer is a silicon oxide layer with a thickness of 1-4nm or an aluminum oxide film with a thickness of 3-50nm.

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