Back contact solar cell, cell module and photovoltaic system

Abstract

The invention is suitable for the field of photovoltaic technology, and provides a back contact solar cell, a cell assembly and a photovoltaic system, the back contact solar cell comprises a first surface and a second surface which are opposite to each other, and a cutting side surface connecting the first surface and the second surface, the first surface is a light facing surface, and the second surface is a backlight surface. The cutting region is adjacent to the first surface, the fracture region is adjacent to the second surface, the p-type doped region and the n-type doped region form a pn junction structure, a pn junction is used as a basic structure for photoelectric conversion of the solar cell, and carriers generated by photons absorbed by the first surface are transmitted to the second surface for separation of the carriers to realize photoelectric conversion. According to the invention, the passivation film layer which is thicker than the cutting area is arranged in the fracture area, high-quality film layer passivation is realized on the backlight surface, the recombination of carriers at the pn junction is reduced, the carriers are fully separated on the second surface, the recombination loss of the carriers is reduced, and the photoelectric conversion efficiency of the cell is improved.

Description

Technical Field

[0001] The present application belongs to the field of photovoltaic technology, and in particular relates to a back-contact solar cell, a battery module and a photovoltaic system. Background Art

[0002] Solar cells are devices that utilize solar energy and directly convert light energy into electrical energy through the photoelectric effect or the photochemical effect. Solar cells include sliced ​​solar cells. Currently, the production of sliced ​​solar cells usually involves cutting solar cells that have already formed multiple film layers to cut the entire solar cell into at least two sliced ​​solar cells, such as two halves. Afterwards, the sliced ​​solar cells are used to make photovoltaic modules. However, after cutting, the morphology of different areas of the cut surface of the sliced ​​solar cell is quite different, resulting in a decrease in the efficiency of the solar cell.

[0003] Application Contents

[0004] The present application provides a back-contact solar cell, aiming to solve the problem that the morphology of different regions of the cut surface of a sliced ​​solar cell varies greatly, resulting in reduced efficiency of the solar cell.

[0005] In a first aspect, the present application provides a back-contact solar cell, the back-contact solar cell comprising a first surface and a second surface opposite to each other, and a cut side surface connecting the first surface and the second surface, the first surface being a light-facing surface, and the second surface being a light-backed surface; a third passivation layer formed on the cut side surface; the cut side surface comprising a cut region adjacent to the first surface and a fracture region adjacent to the second surface; the second surface having alternately arranged p-type doping regions and n-type doping regions, the thickness of the third passivation layer in the cut region being a first thickness, the thickness of the third passivation layer in the fracture region being a second thickness, and the second thickness being greater than the first thickness.

[0006] Optionally, a first area, a second area and a third area are formed on the cutting side surface, the first area, the second area and the third area are located in the cutting area, the first area has a crack structure, the second area has a plurality of first texture structures extending into the first area, the third area has a plurality of second texture structures, at least one of the plurality of first texture structures forms a first angle with the first surface, at least one of the plurality of second texture structures forms a second angle with the first surface, and the angle of the first angle is smaller than the angle of the second angle.

[0007] Optionally, the first angle is greater than 0° and less than or equal to 65°.

[0008] Optionally, the second angle is greater than or equal to 45° and less than or equal to 90°.

[0009] Optionally, the first texture structure extends to the fracture region, and a ratio of a length of the first texture structure to a thickness of the back contact solar cell is greater than 0 and less than or equal to 2.

[0010] Optionally, the second texture structure extends to the fracture region, and a ratio of a length of the second texture structure to a thickness of the back contact solar cell is greater than 0 and less than or equal to 2.

[0011] Optionally, a crack structure is provided in the crack zone, the crack structure and the first surface form a third angle, and the second angle is smaller than the third angle.

[0012] Optionally, the third angle is greater than or equal to 90° and less than or equal to 180°.

[0013] Optionally, the depth of the crack structure is greater than 0 and less than or equal to 5 microns.

[0014] Optionally, a ratio of the length of the crack structure to the thickness of the back contact solar cell is greater than 0 and less than or equal to 0.42.

[0015] Optionally, the thickness of the third passivation layer is greater than or equal to 10 nm and less than or equal to 200 nm.

[0016] Optionally, the third passivation layer includes at least one of a polymer film layer, a silicon oxide film layer and an aluminum oxide film layer.

[0017] Optionally, the difference between the first thickness and the second thickness ranges from 20 to 190 nm.

[0018] Optionally, the first thickness is 10-85 nm.

[0019] Optionally, the second thickness is 30-200 nm.

[0020] Optionally, in the thickness direction of the back-contact solar cell, a ratio of the width of the fracture region to the thickness of the back-contact solar cell is greater than 0 and less than or equal to 1 / 2.

[0021] Optionally, in the thickness direction of the back-contact solar cell, a ratio of the width of the cutting region to the thickness of the back-contact solar cell is greater than 0 and less than or equal to 1 / 2.

[0022] Optionally, it further includes a first passivation layer disposed on the first surface, the third passivation layer has a first portion extending to the first surface, and the first portion covers the first passivation layer.

[0023] Optionally, the thickness of the first passivation layer is 10-200 nm.

[0024] Optionally, it further includes a second passivation layer disposed on the second surface, the third passivation layer has a second portion extending to the second surface, and the second portion covers the second passivation layer.

[0025] Optionally, the second passivation layer has a thickness of 10-200 nm.

[0026] Optionally, it also includes a fourth region and a fifth region formed on the cutting side surface, the fourth region is adjacent to the first surface relative to the fifth region, the fourth region has a molten structure, and the fifth region has a plurality of third texture structures extending to the fourth region.

[0027] Optionally, at least one of the plurality of third texture structures forms a third angle with the first surface, and the angle of the third angle is smaller than the angle of the first angle.

[0028] Optionally, a ratio of an area of ​​the fourth region to a cut side surface of the back contact solar cell is less than or equal to 10%.

[0029] In the present application, the first surface is the light-facing surface, and the second surface is the backlight surface. The cutting area is adjacent to the first surface, and the breaking area is adjacent to the second surface. The second surface includes p-type doped areas and n-type doped areas arranged alternately. The p-type doped areas and the n-type doped areas constitute a pn junction structure. The pn junction serves as the basic structure for photoelectric conversion of solar cells. The carriers generated by absorbing photons on the first surface are transmitted to the second surface for carrier separation to achieve photoelectric conversion. The present application achieves high-quality film passivation on the backlight surface by setting a thicker passivation film layer in the breaking area than in the cutting area, thereby reducing carrier recombination at the pn junction, allowing the carriers to be fully separated on the second surface, reducing carrier recombination losses, and thereby improving the photoelectric conversion efficiency of the battery cell.

[0030] In a second aspect, the present application provides a battery assembly, including the back-contact solar cell. The technical effect of the battery assembly is the same as that of the back-contact solar cell, which will not be described in detail here.

[0031] In a third aspect, the present application provides a photovoltaic system, including the battery assembly. The technical effect of the photovoltaic system is the same as the technical effect of the battery assembly, which will not be described in detail here. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 The structure of the back contact solar cell provided in the present application is shown in FIG. Figure 1 ;

[0033] Figure 2 is a schematic structural diagram of a second texture structure of a back contact solar cell provided in the present application;

[0034] Figure 3 is a schematic structural diagram of a first texture structure of a back contact solar cell provided in the present application;

[0035] Figure 4 The structure of the back contact solar cell provided in the present application is shown in FIG. Figure 2 ;

[0036] Figure 5 The structure of the back contact solar cell provided in the present application is shown in FIG. Figure 3 ;

[0037] Figure 6 It is a schematic structural diagram of the fifth region of the back contact solar cell provided in the present application.

[0038] Description of reference numerals:

[0039] 100, first surface; 200, second surface; 300, cutting side surface; 301, fracture area; 302, cutting area; 303, first area; 304, second area; 305, first texture structure; 306, second texture structure; 307, crack structure; 308, third area; 400, third passivation layer; 401, first part; 402, second part; 500, first passivation layer; 600, second passivation layer; 700, back contact solar cell; 800, cutting line; 801, first cutting line; 802, second cutting line; 803, third cutting line; 804, fourth area; 805, fifth area; 806, molten structure; 807, third texture structure. DETAILED DESCRIPTION

[0040] In order to make the purpose, technical solutions and advantages of the present application clearer, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements with the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present application, and should not be construed as limiting the present application. In addition, it should be understood that the specific embodiments described herein are only used to explain the present application and are not intended to limit the present application.

[0041] In the description of the present application, it should be understood that the terms "length", "width", "up", "down", "left", "right", "horizontal", "top", "bottom", etc., indicating the orientation or position relationship are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0042] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of this application, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0043] In the description of this application, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, an electrical connection, or mutual communication; it can be a direct connection, or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0044] In the present application, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes that the first feature is directly below and obliquely below the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0045] The disclosure below provides many different embodiments or examples to realize the different structures of the present application. In order to simplify the disclosure of the present application, the parts and settings of specific examples are described below. Of course, they are only examples, and the purpose is not to limit the present application. In addition, the present application can repeat reference numbers and / or reference letters in different examples, and this repetition is for the purpose of simplification and clarity, which itself does not indicate the relationship between the various embodiments and / or settings discussed. In addition, the various specific processes and material examples provided by the present application, but those of ordinary skill in the art can appreciate the application of other processes and / or the use of other materials.

[0046] like Figure 1As shown, in the embodiment of the present application, the back contact solar cell 700 includes a first surface 100 and a second surface 200 opposite to each other, and a cutting side surface 300 connecting the first surface 100 and the second surface 200, the cutting side surface 300 includes a cutting area 302 adjacent to the first surface 100 and a fracture area 301 adjacent to the second surface 200, the first surface 100 is a light-facing surface, the second surface 200 is a backlight surface, and the cutting side surface 300 is provided with a third passivation layer 400. It should be noted that in the cell slicing process, the first surface 100 of the cell is damaged to a certain extent by direct external action, so that the cell can be broken or guided to break. For example, the first surface 100 is firstly damaged by mechanical cutting or laser irradiation, and then the entire solar cell is broken by stress changes, thereby forming a complete cutting side surface 300. Among them, the morphological structure produced by cutting is formed in the area of ​​the first surface 100 of the cutting side surface 300 adjacent to the battery cell, and the morphological structure produced by breaking is formed in the area of ​​the second surface 200 of the cutting side surface 300 adjacent to the battery cell. It can be understood that the morphological structure produced by cutting is different from the morphological structure produced by breaking. More specifically, the morphological structure produced by breaking is smoother and flatter than the morphological structure produced by cutting. The setting of the cutting area 302 and the breaking area 301 on the cutting side surface 300 is beneficial to the growth of the subsequent passivation film layer, thereby improving the passivation effect on the cutting side surface 300 of the battery cell.

[0047] In some embodiments, the thickness of the third passivation layer 400 in the cutting area 302 is a first thickness, and the thickness of the third passivation layer 400 in the fracture area 301 is a second thickness, and the second thickness is greater than the first thickness. Since the fracture area 301 is adjacent to the second surface 200, the second surface 200 includes p-type doping areas and n-type doping areas that are alternately arranged. In the cell structure, the p-type doping areas and the n-type doping areas constitute a pn junction structure. The pn junction is the basic structure for the photoelectric conversion of the solar cell. The first surface 100 absorbs photons and generates carriers that are transmitted to the second surface 200 for carrier separation to achieve photoelectric conversion. The present application achieves high-quality film passivation on the backlight surface by setting a thicker passivation film layer in the fracture area 301 than in the cutting area 302, reducing the recombination of carriers at the pn junction, so that the carriers are fully separated on the second surface 200, and the carrier loss is prevented, thereby improving the photoelectric conversion efficiency of the cell. For example, the first thickness may be an average thickness of the third passivation layer 400 in the cutting region 302 , and the second thickness may be an average thickness of the third passivation layer 400 in the fracture region 301 .

[0048] In the related art, the cell segmentation method usually uses laser, which mainly includes two methods: laser melting segmentation and laser non-destructive segmentation. Laser melting segmentation uses laser to ablate the desired position on the surface of the photovoltaic cell to form continuous lines, and then mechanically splits to form sub-cells. This method will cause serious damage to the cut surface. The molten silicon will recrystallize and partially oxidize during the temperature drop, resulting in silicon slag and silicon oxide attached to the surface of the cut surface. The above situation will affect the passivation and other properties of the sliced ​​solar cell, and then affect the photoelectric conversion efficiency of the sliced ​​solar cell. Laser non-destructive segmentation only requires a very short initial laser score 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 segmentation 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, laser non-destructive segmentation can easily cause incomplete segmentation of the cell, and the laser parameters (such as power, focal length, cutting speed, etc.) need to be continuously debugged to achieve complete segmentation of the cell. For example, for cells of different thicknesses, the energy density and focus depth of the laser beam need to be adjusted to ensure that the laser can penetrate the entire thickness of the cell and achieve effective cutting. If the laser energy is insufficient or the focus depth is inappropriate, it will lead to incomplete cutting or reduced cutting quality. Alternatively, for thicker cells, the cutting speed needs to be reduced to ensure that the laser beam has enough time to heat and cut the material. If the cutting speed is too fast, the laser beam may not stay on the surface of the material for enough time, resulting in incomplete cutting or the formation of burrs. Alternatively, cells of different thicknesses have different material properties, such as hardness, thermal conductivity, melting point, etc. These properties will affect the effect of laser cutting. Thicker cells may have higher hardness and thermal conductivity, requiring higher laser energy and longer cutting time to achieve effective cutting. There are many factors that affect the cutting of battery cells, which are interrelated and difficult to debug through a single variable control. There is a lack of clear indicators to serve as a reference during the debugging process. It is necessary to rely on experience and spend a lot of time and energy to conduct multiple experimental verifications until the setting parameters that can stably and reliably slice the battery cells are obtained. If different types of battery cells need to be replaced, the above experimental verification steps need to be repeated, which greatly limits the production capacity of the battery cells. In addition, the battery cells that have not been completely split during this period can only be discarded, resulting in waste and loss of silicon wafer materials.

[0049] In response to the above problems, the R&D personnel discovered through extensive research that the crack structure 307 formed on the cutting side surface 300 can serve as a landmark indicator of complete cutting of the battery cell. By controlling the formation of the crack structure 307 in the cutting side surface 300, it can ensure that battery cells of different thicknesses are cut. This greatly simplifies the debugging of the equipment. There is no need for complicated debugging of battery cells of different thicknesses. It is only necessary to ensure that the cutting equipment can form stable cracks on the cutting side surface 300 to achieve complete cutting of the battery cell.

[0050] like Figure 2 As shown, in some embodiments, the cutting side surface includes a first region, a second region and a third region, the first region, the second region and the third region are located in the cutting region, and the first region has a crack structure. It can be understood that the first region 303 is a region having a crack structure 307 in the cutting region 302, the second region 304 and the first region are arranged relative to each other in the thickness direction of the battery cell, the first region is adjacent to the first surface relative to the second region, and a plurality of first texture structures extend from the second region to the first region, the first region 303 can be a continuous region formed in the cutting region 302, and the first region 303 can also be a discontinuous region formed in the cutting region 302. For example, the range of the first region 303 can be determined by the boundary range of the crack structure 307, and the existence of the first region 303 can ensure that the battery cell is completely cut. The third region 308 and the first region 303 are arranged relative to each other in the cutting direction of the battery cell, and a plurality of second texture structures 306 are formed in the third region 308, and the second texture structures 306 in the third region 308 and the first texture structures 305 in the second region are independent of each other.

[0051] It should be noted that the first area 303 may be partially formed in the cutting area 302, or the first area 303 may be completely formed in the cutting area 302, which is determined according to the requirements of the production process and is not limited in this application.

[0052] like Figure 2 and Figure 3As shown, further, in the embodiment of the present application, the second region has a plurality of first texture structures 305 extending into the first region, the third region has a plurality of second texture structures 306, at least one of the plurality of first texture structures 305 forms a first angle with the first surface 100, the third region 308 has a second texture structure 306, at least one of the plurality of second texture structures 306 forms a second angle with the first surface 100, and the angle of the first angle is smaller than the angle of the second angle. Exemplarily, the first angle formed by the first texture structure 305 and the second surface 200 can be understood as the angle a formed by the extension direction of the first texture structure 305 toward the first surface 100 and the first surface 100, and the second angle formed by the second texture structure 306 and the first surface 100 can be understood as the angle b formed by the extension direction of the second texture structure 306 toward the first surface 100 and the first surface 200. The present application controls the morphological structure of the first texture structure 305 and the morphological structure of the second texture structure 306 so that the angle of the first angle is smaller than the angle of the second angle, which helps to reduce the number and length of cracks, thereby reducing the damage caused during the cutting process and significantly improving the cutting quality.

[0053] In some embodiments, the first angle is greater than 0° and less than or equal to 65°. Preferably, the first angle is greater than or equal to 20° and less than or equal to 45°. In such an embodiment, the first angle can be 20°, 30°, 40°, 45° or any value between 20° and 45°, and is not specifically limited here. A smaller first angle means that the crack is more restricted during the expansion process, which helps to reduce the number and length of the cracks, thereby reducing the damage caused during the cutting process.

[0054] In some embodiments, the second angle is greater than or equal to 45° and less than or equal to 90°. In such an embodiment, the second angle can be 45°, 50°, 55°, 60°, 70°, 80°, 90° or any value between 45° and 90°, which is not limited here. A larger second angle indicates that the texture of the third area 308 is more regular and continuous, which helps to maintain the flatness and smoothness of the cut side surface 300.

[0055] In some embodiments, the difference between the angle of the first angle and the angle of the second angle is 10° to 30°. In such an embodiment, the difference between the angle of the first angle and the angle of the second angle can be 10°, 20°, 25°, 30° or any value between 10° and 30°, and is not specifically limited here. By optimizing the texture structure morphology of the first texture structure and the second texture structure and the angle difference, the difference between the angle of the first angle and the angle of the second angle is controlled within this range, the photoelectric conversion efficiency of the solar cell can be improved and the performance of the product can be improved.

[0056] In some embodiments, the first texture structure 305 extends to the fracture region 301, and the ratio of the length of the first texture structure 305 to the thickness of the back contact solar cell 700 is greater than 0 and less than or equal to 2. Preferably, the ratio of the length of the first texture structure 305 to the thickness of the back contact solar cell 700 is greater than or equal to 1 and less than or equal to 2. In such an embodiment, the ratio of the length of the first texture structure 305 to the thickness of the back contact solar cell 700 can be 1, 1.2, 1.4, 1.6, 1.8, 2 or any value between 1 and 2, and is not specifically limited herein. It can be understood that the first texture structure 305 is a continuous texture structure, extending from the cutting region 302 to the fracture region 301 on the cutting side surface 300. When the ratio of the length of the texture structure to the thickness of the battery is appropriate, it can effectively absorb and disperse the energy during crack propagation, thereby slowing down or preventing the further propagation of the crack.

[0057] In some embodiments, the second texture structure 306 extends to the fracture region 301, and the ratio of the length of the second texture structure 306 to the thickness of the back contact solar cell 700 is greater than 0 and less than or equal to 2. Preferably, the ratio of the length of the second texture structure 306 to the thickness of the back contact solar cell 700 is greater than or equal to 1 and less than or equal to 2. In such an embodiment, the ratio of the length of the second texture structure 306 to the thickness of the back contact solar cell 700 can be 1, 1.2, 1.4, 1.6, 1.8, 2 or any value between 1 and 2, and is not specifically limited herein. It can be understood that the second texture structure 306 is a continuous texture structure, extending from the cutting region 302 to the fracture region 301 on the cutting side surface 300. When the ratio of the length of the texture structure to the thickness of the battery is appropriate, it can effectively absorb and disperse the energy during crack propagation, thereby slowing down or preventing the further propagation of the crack.

[0058] In some embodiments, a crack structure 307 is provided in the first region 303, and the crack structure 307 and the first surface 100 form a third angle, and the angle of the second angle is less than the angle of the third angle. Exemplarily, the third angle formed by the crack structure 307 and the first surface 100 can be understood as the angle c formed by the extension direction of the crack structure 307 toward the first surface 100 and the first surface 100, and the existence of the angle c can guide the depth and width distribution of the crack to be more uniform. Since the third angle is greater than the second angle, the crack may be subjected to greater resistance or guidance during the expansion process, resulting in a change in the expansion path of the crack. This change helps to reduce the damage of the crack to the overall structure of the material. In addition, the presence of the crack structure 307 will enhance the local strength of the material by changing the stress distribution of the material. Further, the third angle is greater than or equal to 90° and less than or equal to 180°. In such an embodiment, the third angle may be 90°, 100°, 110°, 120°, 150°, 170°, 180° or any value between 90° and 180°, and is not specifically limited herein.

[0059] In some embodiments, the depth of the crack structure 307 is greater than 0 and less than or equal to 5 microns. Preferably, the depth of the crack structure 307 is greater than 0.1 microns and less than or equal to 3 microns. In such an embodiment, the depth of the crack structure 307 can be 0.1 microns, 0.2 microns, 1 micron, 2 microns, 2.5 microns, 3 microns or any value between 0.1 microns and 3 microns, and is not specifically limited here. At this time, the uniformity of the coating and the light trapping effect during the passivation process can be guaranteed.

[0060] Further, the ratio of the length of the crack structure 307 to the thickness of the back contact solar cell 700 is greater than 0 and less than or equal to 0.42. Preferably, the ratio of the length of the crack structure 307 to the thickness of the back contact solar cell 700 is greater than or equal to 0.1 and less than or equal to 0.42. Exemplarily, the ratio of the length of the crack structure 307 to the thickness of the back contact solar cell 700 can be 0.1, 0.2, 0.3, 0.4, 0.42 or any value between 0.1-0.42, and is not specifically limited herein. When the ratio of the length of the crack structure 307 to the thickness of the back contact solar cell 700 is within this range, the damage of the crack structure 307 to the cut side surface 300 can be effectively reduced, which is beneficial to the growth of the subsequent passivation film layer and improves the passivation effect of the cut side surface 300 of the cell.

[0061] like Figure 1As shown, in some embodiments, the thickness of the third passivation layer 400 is greater than or equal to 10nm and less than or equal to 200nm. For example, the thickness of the third passivation layer 400 can be 10nm, 30nm, 35nm, 40nm, 45nm, 50nm, 55nm, 60nm, 65nm, 70nm, 90nm, 100nm, 120nm, 125nm, 140nm, 150nm, 170nm, 175nm, 180nm, 190nm, 195nm or 200nm. The thickness of the third passivation layer 400 within this range can ensure the passivation quality of the cut side surface 300 and achieve complete passivation of the cut side surface 300. Further, too thin a passivation layer thickness will result in insufficient passivation effect, and the marginal effect of the passivation effect obtained by the excessive passivation layer thickness is reduced, and the process time and material consumption are increased. Furthermore, the third passivation layer 400 includes at least one of a polymer film layer, a silicon oxide film layer and an aluminum oxide film layer. Specifically, in one optional manner, the third passivation layer 400 is a silicon oxide film layer or an aluminum oxide film layer, and the passivation film layer can be prepared by physical vapor deposition (PVD) or chemical vapor deposition (CVD). In another optional manner, the third passivation layer 400 is a polymer film layer, and a uniform passivation film layer can be formed on the cut side surface 300 by spin coating. When the above technical solution is adopted, the third passivation layer 400 can passivate the cut side surface 300, reduce the recombination rate of carriers at the cut side surface 300, and further improve the photoelectric conversion efficiency of the solar cell.

[0062] Further, the first thickness is 10-85 nm. For example, the first thickness can be 10 nm, 20 nm, 30 nm, 40 nm, 60 nm, 70 nm, 85 nm or any value between 10-85 nm, and is not limited here. The first thickness within this range can ensure the passivation quality of the cutting area 302 and achieve complete passivation of the cutting area 302.

[0063] Exemplarily, the second thickness is 30 to 200 nm. Exemplarily, the second thickness can be 30 nm, 40 nm, 60 nm, 70 nm, 85 nm, 100 nm, 150 nm, 200 nm, or any value between 30 and 200 nm, and is not specifically limited here. The second thickness within this range can ensure the passivation quality of the fracture region 301 and achieve complete passivation of the fracture region 301.

[0064] Exemplarily, the difference between the first thickness and the second thickness ranges from 20 to 190 nm. The difference between the first thickness and the second thickness can be 20 nm, 40 nm, 60 nm, 70 nm, 85 nm, 100 nm, 150 nm, 190 nm or any value between 20 and 190 nm, and is not specifically limited here. The difference between the first thickness and the second thickness within this range can easily achieve differentiated film passivation of different areas of the cut side surface 300 of the cell, thereby improving the overall conversion efficiency of the solar cell.

[0065] In some embodiments, the ratio of the total area of ​​the first region 303 to the area of ​​the cut side surface 300 is greater than 0 and less than or equal to 15%. Preferably, the ratio of the total area of ​​the first region 303 to the area of ​​the cut side surface 300 is greater than or equal to 0.1% and less than or equal to 10%. In such an embodiment, the ratio of the total area of ​​the first region 303 to the area of ​​the cut side surface 300 can be 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, 8%, 10%, or any value between 0.1% and 10%, and is not specifically limited here. By controlling the total area of ​​the first region 303 within this range, it is possible to ensure that the crack structure 307 generated on the cut side surface 300 is small, the specific surface area of ​​the cut side surface 300 is small, and the dangling bonds on the cut side surface 300 are reduced, thereby reducing the carrier recombination on the cut side surface 300 and improving the photoelectric conversion efficiency of the battery cell.

[0066] In some embodiments, in the thickness direction of the back contact solar cell 700, the ratio of the width of the fracture region 301 to the thickness of the back contact solar cell 700 is greater than 0 and less than or equal to 1 / 2. Exemplarily, the ratio of the width of the fracture region 301 to the thickness of the back contact solar cell 700 may be 1 / 5, 1 / 4, 1 / 3 or 1 / 2. The width of the fracture region 301 within this range helps to inhibit the further expansion of the crack inside the battery. This can reduce the damage of the crack to the battery structure and improve the overall stability of the battery. In other embodiments, in the thickness direction of the back contact solar cell 700, the ratio of the width of the cutting region 302 to the thickness of the back contact solar cell 700 is greater than 0 and less than or equal to 1 / 2. It can be understood that, exemplarily, the ratio of the width of the cutting region 302 to the thickness of the back contact solar cell 700 may be 1 / 5, 1 / 4, 1 / 3 or 1 / 2. The width of the cutting area 302 is within this range, which can reduce light scattering and reflection loss caused by cracks and improve the light absorption efficiency of the solar cell, which helps to improve the photoelectric conversion performance of the cell.

[0067] In some embodiments, the first surface 100 is provided with a first passivation layer 500, and the third passivation layer 400 has a first portion 401 extending to the first surface 100, and the first portion 401 covers the first passivation layer 500. In this way, the edge portion of the cell can be covered, and the edge portion of the cell has a film layer structure consistent with the first surface 100, which can efficiently passivate the edge portion, thereby reducing the recombination of the edge portion and improving the conversion efficiency of the solar cell. In addition, the first portion 401 of the third passivation layer 400 extending to the first surface 100 and the first passivation layer 500 can jointly form a double passivation mechanism, which can greatly reduce the number of carriers of one polarity reaching the surface, thereby significantly reducing the recombination loss on the substrate surface and improving the performance of the cell. Further, the thickness of the first passivation layer 500 is 10 to 200 nm. For example, the thickness of the first passivation layer 500 can be 10 nm, 30 nm, 35 nm, 40 nm, 45 nm, 50 nm, 55 nm, 60 nm, 65 nm, 70 nm, 90 nm, 100 nm, 120 nm, 125 nm, 140 nm, 150 nm, 170 nm, 175 nm, 180 nm, 190 nm, 195 nm or 200 nm, etc. The thickness of the first passivation layer 500 within this range can ensure the passivation quality of the first surface 100 and reduce the recombination loss of carriers on the first surface 100.

[0068] In some embodiments, the second surface 200 is provided with a second passivation layer 600, and the third passivation layer 400 has a second portion 402 extending to the second surface 200, and the second portion 402 covers the second passivation layer 600. In this way, the edge portion of the cell can be covered, and the edge portion of the cell has a film layer structure consistent with the second surface 200, which can efficiently passivate the edge portion, thereby reducing the recombination of the edge portion and improving the conversion efficiency of the solar cell. In addition, the second portion 402 of the third passivation layer 400 extending to the second surface 200 and the second passivation layer 600 can form a double passivation mechanism together, which can greatly reduce the number of carriers of one polarity reaching the surface, thereby significantly reducing the recombination loss on the substrate surface and improving the performance of the cell. Further, the thickness of the second passivation layer 600 is 10 to 200 nm. For example, the thickness of the second passivation layer 600 can be 10 nm, 30 nm, 35 nm, 40 nm, 45 nm, 50 nm, 55 nm, 60 nm, 65 nm, 70 nm, 90 nm, 100 nm, 120 nm, 125 nm, 140 nm, 150 nm, 170 nm, 175 nm, 180 nm, 190 nm, 195 nm or 200 nm, etc. The thickness of the second passivation layer 600 within this range can ensure the passivation quality of the second surface 200 and reduce the recombination loss of carriers on the second surface 200.

[0069] In other embodiments, the thickness of the second portion 402 is greater than the thickness of the first portion 401. Since the backlight surface is in contact with the metal electrode, charge recombination is more likely to occur, so increasing the thickness of the passivation film extending from the third passivation layer 400 to the backlight surface can more effectively prevent charge recombination, improve the photoelectric conversion efficiency of the battery, and provide stronger protection for the backlight surface of the battery cell to prevent damage to the battery cell by the external environment, such as oxidation, corrosion, etc., which helps to extend the service life of the battery cell.

[0070] like Figure 4 As shown, in some embodiments, a cutting line 800 is defined on the second surface of the initial solar cell sheet, and the cutting line 800 includes a first cutting line 801, a second cutting line 802 and a third cutting line 803. In the extension direction of the third cutting line 803, the first cutting line 801 and the second cutting line 802 are respectively located at two ends of the third cutting line 803; the initial solar cell sheet is cut by a melting laser along the first cutting line 801 and the second cutting line 802 to form a cutting groove, and the depth of the melting laser cutting is at least 50% of the thickness of the initial solar cell sheet; after the cutting groove is formed on the first surface of the initial solar cell sheet by the melting laser, the initial solar cell sheet is heated by a non-destructive laser along the third cutting line 803, and while the initial solar cell is heated, the initial solar cell sheet is simultaneously sprayed and cooled along the path of the third cutting line 803, and the spray cooling step causes the initial solar cell sheet to be cracked along the cutting groove to form the back contact solar cell 700 of the present application, thereby forming a cutting side surface on the side surface of the back contact solar cell 700 along the positions of the first cutting line 801, the second cutting line 802 and the third cutting line 803.

[0071] like Figure 5 As shown, a fourth region 804 and a fifth region 805 are also formed on the cut side surface of the back contact solar cell 700 along the positions of the first cutting line 801 and the second cutting line 802. The fourth region is adjacent to the first surface relative to the fifth region. The fourth region has a molten structure 806. The fifth region 805 has a plurality of third texture structures 807 extending to the fourth region 804. The fourth region 804 is severely damaged, and slag and silicon oxide will be attached to the side surface of the back contact solar cell 700. Therefore, an alkaline or acidic cleaning solution is required for subsequent cleaning to remove part of the silicon slag and silicon oxide on the molten side surface. It can be understood that due to the serious damage caused by the melting laser, the total area of ​​the fourth region is as small as possible. Preferably, the ratio of the total area of ​​the fourth region to the cut side surface of the back contact solar cell 700 is less than or equal to 10% to reduce damage to the side surface of the back contact solar cell 700.

[0072] like Figure 6As shown, further, at least one of the plurality of third texture structures 807 forms a third angle d with the first surface 100, and the angle of the third angle d is smaller than the angle of the first angle a. The formation of the third texture structure 807 can disperse the splinter stress, reduce the formation of the molten structure in the fourth region 804, and reduce the damage of the molten structure to the cut side surface.

[0073] In this embodiment, the initial solar cell is first grooved along the first cutting line 801 and the second cutting line 802 to form a cutting groove, and then the initial solar cell of at least a part of the thickness is heated along the third cutting line 803, and then the initial solar cell is sprayed and cooled along the third cutting line 803, so that the initial solar cell undergoes a rapid high-temperature-low-temperature change in a short period of time at the position of the third cutting line 803. Due to the effect of thermal expansion and contraction, this part of the solar cell undergoes a severe deformation. Since other surrounding areas are not concentrated areas of heating and cooling, although heat conduction occurs and temperature changes occur, they are not as severe as the solar cell in the concentrated area of ​​temperature change, that is, the area below the third cutting line 803. Therefore, due to the difference in deformation speed and degree, natural fracture occurs. And due to the existence of the cutting groove, the cracking process can be cracked along the cutting groove. After the cracking of the initial solar cell is completed, the cut side surface is passivated to avoid some irreversible defects caused by the environmental influence on the cut side surface. In this way, the dangling bonds and defects generated during the cracking process can be effectively reduced, thereby effectively improving the conversion efficiency of the solar cell.

[0074] The photovoltaic system in the embodiment of the present application may include the battery assembly in the embodiment of the present application, and the battery assembly in the embodiment of the present application may include several back-contact solar cells in the embodiment of the present application. Of course, the battery assembly may also include a back plate and a glass plate. A plurality of battery cells are arranged between the back plate and the glass plate, and welding strips (bus bars, interconnecting strips), conductive back plates, etc. are provided on the battery cells to realize the series connection of the battery cells.

[0075] In the description of this specification, the description with reference to the terms "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials, or characteristics described in conjunction with the embodiments or examples are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0076] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims

1. A back contact solar cell, characterized in that: The back contact solar cell comprises a first surface and a second surface opposite to each other, and a cut side surface connecting the first surface and the second surface, the first surface is a light-facing surface, and the second surface is a backlight surface; a third passivation layer formed on the cut side surface; the cut side surface comprising a cut region adjacent to the first surface and a fracture region adjacent to the second surface; The second surface has p-type doped regions and n-type doped regions arranged alternately, the thickness of the third passivation layer in the cutting region is a first thickness, the thickness of the third passivation layer in the breaking region is a second thickness, and the second thickness is greater than the first thickness.

2. The back contact solar cell according to claim 1, characterized in that A first area, a second area and a third area are formed on the cutting side surface, the first area, the second area and the third area are located in the cutting area, the first area has a crack structure, the second area has a plurality of first texture structures extending into the first area, the third area has a plurality of second texture structures, at least one of the plurality of first texture structures forms a first angle with the first surface, at least one of the plurality of second texture structures forms a second angle with the first surface, and the angle of the first angle is smaller than the angle of the second angle.

3. The back contact solar cell according to claim 2, characterized in that: The first angle is greater than 0° and less than or equal to 65°.

4. The back contact solar cell according to claim 2, characterized in that: The second angle is greater than or equal to 45° and less than or equal to 90°.

5. The back contact solar cell according to claim 2, characterized in that: The difference between the first angle and the second angle is 10° to 30°.

6. The back contact solar cell according to claim 2, characterized in that: A ratio of a total area of ​​the first region to an area of ​​the cutting side surface is greater than 0 and less than or equal to 15%.

7. The back contact solar cell according to claim 1, characterized in that: The first texture structure extends to the fracture region, and a ratio of a length of the first texture structure to a thickness of the back contact solar cell is greater than 0 and less than or equal to 2.

8. The back contact solar cell according to claim 2, characterized in that: The second texture structure extends to the fracture region, and a ratio of a length of the second texture structure to a thickness of the back contact solar cell is greater than 0 and less than or equal to 2.

9. The back contact solar cell according to claim 2, characterized in that: The crack structure and the first surface form a third angle, and the second angle is smaller than the third angle.

10. The back contact solar cell according to claim 9, characterized in that: The third angle is greater than or equal to 90° and less than or equal to 180°.

11. The back contact solar cell according to claim 9, characterized in that: The depth of the crack structure is greater than 0 and less than or equal to 5 microns.

12. The back contact solar cell according to claim 9, characterized in that: A ratio of the length of the crack structure to the thickness of the back contact solar cell is greater than 0 and less than or equal to 0.

42.

13. The back contact solar cell according to claim 1, wherein: The thickness of the third passivation layer is greater than or equal to 10 nm and less than or equal to 200 nm.

14. The back contact solar cell according to claim 1, wherein: The third passivation layer includes at least one of a polymer film layer, a silicon oxide film layer and an aluminum oxide film layer.

15. The back contact solar cell according to claim 1, wherein: The difference between the first thickness and the second thickness ranges from 20 to 190 nm.

16. The back contact solar cell according to claim 1, characterized in that The first thickness is 10-85 nm.

17. The back contact solar cell according to claim 1, wherein: The second thickness is 30-200 nm.

18. The back contact solar cell according to claim 1, wherein: In the thickness direction of the back-contact solar cell, a ratio of a width of the fracture region to a thickness of the back-contact solar cell is greater than 0 and less than or equal to 1 / 2.

19. The back contact solar cell according to claim 1, wherein: In the thickness direction of the back-contact solar cell, a ratio of a width of the cutting region to a thickness of the back-contact solar cell is greater than 0 and less than or equal to 1 / 2.

20. The back contact solar cell according to claim 1, wherein: The device further includes a first passivation layer disposed on the first surface. The third passivation layer has a first portion extending to the first surface, and the first portion covers the first passivation layer.

21. The back contact solar cell according to claim 20, characterized in that The thickness of the first passivation layer is 10-200 nm.

22. The back contact solar cell according to claim 1, wherein: It also includes a second passivation layer disposed on the second surface, the third passivation layer has a second portion extending to the second surface, and the second portion covers the second passivation layer.

23. The back contact solar cell according to claim 22, characterized in that The thickness of the second passivation layer is 10-200 nm.

24. The back contact solar cell according to claim 1, characterized in that It also includes a fourth region and a fifth region formed on the cut side surface, wherein the fourth region is adjacent to the first surface relative to the fifth region, the fourth region has a molten structure, and the fifth region has a plurality of third texture structures extending to the fourth region.

25. The back contact solar cell according to claim 24, characterized in that At least one of the plurality of third texture structures forms a third angle with the first surface, and the angle of the third angle is smaller than the angle of the first angle.

26. The back contact solar cell according to claim 24, characterized in that The ratio of the area of ​​the fourth region to the cut side surface of the back contact solar cell is less than or equal to 10%.

27. A battery assembly, characterized in that: Comprising a back-contact solar cell as described in any one of claims 1-26.

28. A photovoltaic system, characterized in that: Comprising a battery assembly as claimed in claim 27.

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