Solar cell, photovoltaic module and preparation method of solar cell

Abstract

The invention discloses a solar cell, a photovoltaic module and a preparation method of the solar cell, relates to the technical field of solar cells, and aims to solve the problems that the color difference of two areas with a passivation layer and without the passivation layer in a light-facing surface (or a backlight surface) of a fragmented solar cell is large; therefore, the problems of large visual difference and low aesthetic degree of the solar cell are solved. The solar cell comprises a first surface and a second surface which are opposite to each other, and a side surface connecting the first surface and the second surface; the side surface includes a cut surface. The solar cell includes: a first passivation layer formed on a cut surface; and a plurality of second passivation layers which are distributed at intervals and are formed on an edge area, adjacent to the cutting surface, in the first surface and / or the second surface.

Description

Technical Field

[0001] The invention relates to the technical field of solar cells, and in particular to a solar cell, a photovoltaic module and a method for preparing the solar cell. Background Art

[0002] A solar cell is a device that utilizes solar energy and directly converts 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 a solar cell that has formed multiple film layers to cut the entire solar cell into at least two sliced ​​solar cells, such as two half slices. Afterwards, a passivation layer is formed on the cut surface of the sliced ​​solar cell.

[0003] During this process, a continuously distributed passivation layer will also be plated on the edge areas of the light-facing and back-light surfaces of the sliced ​​solar cell that are adjacent to the cut surface. At this time, the color difference between the two areas with the passivation layer and the area without the passivation layer on the light-facing (or back-light) surface of the sliced ​​solar cell is large, resulting in a large visual difference in the solar cell, low aesthetics, and may affect the poor connection of the component solder strips. Summary of the invention

[0004] The object of the present invention is to provide a solar cell, a photovoltaic module and a method for preparing a solar cell, which are used to reduce the visual difference of the solar cell, improve the aesthetics of the solar cell, and eliminate poor connection of welding strips and the like.

[0005] In order to achieve the above-mentioned object, in a first aspect, the present invention provides a solar cell. The solar cell comprises a first surface and a second surface opposite to each other, and a side surface connecting the first surface and the second surface; the side surface comprises a cut surface. The solar cell comprises: a first passivation layer formed on the cut surface; and a plurality of second passivation layers distributed at intervals formed on the edge region of the first surface and / or the second surface adjacent to the cut surface.

[0006] In the solar cell provided by the present invention, a plurality of second passivation layers are distributed at intervals on the edge region, that is, the second passivation layer formed on the first surface and / or the second surface is discontinuous. Compared with the prior art, the continuously distributed passivation layer formed on the edge region adjacent to the cut surface in the light-facing surface and the backlight surface of the sliced ​​solar cell, when the area of ​​the edge region involved in the present invention and the prior art is completely equal or substantially equal or the edge region in the present invention is smaller than the edge region in the prior art, the proportion of the second passivation layer formed in the present invention in the first surface and / or the second surface is reduced. Based on this, the first surface and / or the second surface visually present a more uniform color, and the color difference of different regions of the first surface and / or the second surface is reduced compared to the solar cell in the prior art, the visual difference of the solar cell is reduced, and the aesthetics of the solar cell is improved. Further, the plurality of second passivation layers distributed at intervals in the present invention can also reduce the influence on the surface refractive index of the first surface and / or the second surface, and improve the PL (photoluminescence) brightness, thereby improving the cell efficiency of the solar cell. Furthermore, an electrode structure is formed on the first surface and / or the second surface of the solar cell. In the prior art, the electrode structure closer to the edge of the solar cell is easily covered by the continuously distributed second passivation layer, which affects the connection between the welding tape and other connectors and the electrode structure, thereby affecting the quality of the final component. However, since the multiple second passivation layers in the present invention are distributed at intervals, the probability of the electrode structure near the edge of the solar cell being completely covered can be reduced or eliminated, thereby improving the connection stability between the welding tape and other connectors and the electrode structure, so as to improve the quality of the final photovoltaic component. In addition, since the first passivation layer is formed on the cut surface, the first passivation layer can passivate the cut surface, reduce the recombination rate of photogenerated carriers at the cut surface, and improve the photoelectric conversion efficiency of the solar cell.

[0007] In one implementation, a plurality of second passivation layers are distributed in the edge region in an island shape.

[0008] When adopting the above-mentioned technical solution, multiple island-shaped distributed second passivation layers are beneficial for light to pass through the side walls of the second passivation layer and reflect more light to the texture structure between two spaced-apart second passivation layers, thereby improving the light trapping effect of the first surface and / or the second surface of the solar cell, increasing the absorbance, so as to improve the utilization rate of light by the first surface and / or the second surface of the solar cell, thereby improving the photoelectric conversion efficiency of the solar cell.

[0009] In one implementation, along the thickness direction of the solar cell, the plane shape of the second passivation layer is a triangle, a quadrilateral, a pentagon, or a closed figure consisting of an arc and a line segment.

[0010] In one implementation, the second passivation layer includes an end portion close to the first surface and / or the central area of ​​the second surface, and the end portions of the plurality of second passivation layers are wavy or sawtooth-shaped.

[0011] When the above technical solution is adopted, compared with the case where the end boundaries of the plurality of second passivation layers are linear, the proportion of the second passivation layer in the first surface and / or the second surface can be further reduced. Based on this, the visual difference of the solar cell can be further reduced and the aesthetics of the solar cell can be improved.

[0012] In one implementation, the side surface further includes a non-cut side surface adjacent to the cut surface, and a plurality of second passivation layers distributed at intervals are further formed on edge regions of the non-cut side surface adjacent to the cut surface.

[0013] When the above technical solution is adopted, compared with the prior art in which a continuously distributed passivation layer is formed on the non-cut side surface, the multiple second passivation layers distributed at intervals in the present invention can also reduce the impact on the surface refractive index of the non-cut side surface, further improving the cell efficiency of the solar cell. Furthermore, the multiple second passivation layers distributed at intervals are conducive to the light passing through its side wall to reflect more light to the texture structure between two second passivation layers distributed at intervals, thereby improving the light trapping effect of the non-cut side surface of the solar cell, increasing the light absorption rate, so as to improve the utilization rate of the non-cut side surface of the solar cell for light, thereby improving the photoelectric conversion efficiency of the solar cell.

[0014] In one implementation, the plurality of second passivation layers include at least one second passivation layer spaced apart from the first passivation layer.

[0015] In one implementation, along the vertical direction from the edge area of ​​the first surface to the center area of ​​the first surface, the width of the second passivation layer on the first surface is greater than or equal to 0 mm and less than or equal to 1 mm; and / or, along the vertical direction from the edge area of ​​the second surface to the center area of ​​the second surface, the width of the second passivation layer on the second surface is greater than or equal to 0 mm and less than or equal to 1 mm.

[0016] When the above technical solution is adopted, not only can the aesthetics, surface refractive index, and PL brightness of solar cells be significantly improved, thereby improving the cell efficiency of solar cells; at the same time, it will not affect the connection between connectors such as welding strips and electrode structures, thereby improving the quality of the final components.

[0017] In one implementation, the thickness of the first passivation layer is greater than the thickness of the second passivation layer.

[0018] When the above technical solution is adopted, the passivation effect of the first passivation layer on the cut surface can be improved, the recombination rate of photogenerated carriers at the cut surface can be further reduced, and the photoelectric conversion efficiency of the solar cell can be improved. Furthermore, since the thickness of the second passivation layer is relatively thin, it can not only reduce the influence of the second passivation layer on the surface refractive index and improve the cell efficiency of the solar cell, but also reduce the visual difference of the solar cell and improve the aesthetics of the solar cell.

[0019] In one implementation, the thickness of the first passivation layer is greater than or equal to 10 nm and less than or equal to 300 nm.

[0020] In a second aspect, the present invention further provides a photovoltaic module. The photovoltaic module comprises: a battery string and an encapsulation layer. The battery string is formed by connecting a plurality of solar cells as described in the above technical solution, and the encapsulation layer is used to cover the surface of the battery string.

[0021] Compared with the prior art, the beneficial effects of the photovoltaic module provided by the present invention are the same as the beneficial effects of the solar cell described in the above technical solution, which will not be described in detail here.

[0022] In a third aspect, the present invention further provides a method for preparing a solar cell. The method for preparing a solar cell comprises:

[0023] Providing a semiconductor substrate;

[0024] The semiconductor substrate is divided into at least two semiconductor substrate slices; the semiconductor substrate slices include a first surface and a second surface opposite to each other, and a side surface connecting the first surface and the second surface; the side surface includes a cutting surface;

[0025] forming a first passivation layer on the cut surface;

[0026] A plurality of second passivation layers distributed at intervals are formed on edge regions of the first surface and / or the second surface adjacent to the cut surface.

[0027] Compared with the prior art, the beneficial effects of the method for preparing a solar cell provided by the present invention are the same as the beneficial effects of the solar cell described in the above technical solution, and will not be described in detail here.

[0028] In one implementation, the temperature for forming the first passivation layer and the second passivation layer is less than or equal to 100°C.

[0029] For the convenience of subsequent description, the first passivation layer and the second passivation layer are collectively referred to as passivation layers. Compared with the high-temperature process used in the prior art to form the passivation layer, the temperature of the present invention when forming the passivation layer is lower than the temperature in the prior art, which can reduce or avoid the damage to the film layer already formed on the semiconductor substrate during the process of forming the passivation layer. For example, it is possible to avoid damaging the surface protection film already formed on the semiconductor substrate to avoid releasing organic matter, thereby avoiding damaging the edge passivation effect, so as to ensure the yield and component power of the solar cell.

[0030] In one implementation, the method for preparing a solar cell further includes heat treating the first passivation layer and / or the second passivation layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0032] Figure 1 A schematic diagram of the distribution of the passivation layer on the light-facing surface in the prior art;

[0033] Figure 2 A physical picture of five stacked solar cells in the prior art;

[0034] Figure 3 The structure of the solar cell in the embodiment of the present invention is shown in FIG. Figure 1 ;

[0035] Figure 4 In the embodiment of the present invention Figure 3 A schematic structural diagram of a first surface;

[0036] Figure 5 The structure of the solar cell in the embodiment of the present invention is shown in FIG. Figure 2 ;

[0037] Figure 6 A schematic diagram of the relationship between light and a solar cell in an embodiment of the present invention;

[0038] Figure 7 : is a SEM image of a solar cell in an embodiment of the present invention.

[0039] Reference numerals:

[0040] 1-first surface, 2-first passivation layer, 3-second passivation layer, 4-non-cut side surface, 5-light-facing surface, 6-passivation layer, 7-normal area. DETAILED DESCRIPTION

[0041] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0042] It should be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it can be directly on the other element or indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or indirectly connected to the other element.

[0043] 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. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "multiple" is two or more, unless otherwise clearly and specifically defined. The meaning of "several" is one or more, unless otherwise clearly and specifically defined.

[0044] In the description of the present invention, it is necessary to understand that the directions or positional relationships indicated by the terms "up", "down", "front", "back", "left", "right", etc. are based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as a limitation on the present invention.

[0045] In the description of the present invention, 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 or an electrical connection; 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 the present invention can be understood according to specific circumstances.

[0046] The background of using half-cell solar cells in photovoltaic modules can be traced back to decades ago, when solar energy technology was not yet mature and the production cost of full-cell photovoltaic modules (i.e. photovoltaic modules made of a whole solar cell) was high. Therefore, in order to reduce costs and improve the efficiency of photovoltaic modules, half-cell photovoltaic modules (i.e. photovoltaic modules made of half-cell solar cells) were introduced and gradually became widely used.

[0047] Half-cell photovoltaic modules are made by cutting standard-sized silicon wafers into two halves according to a specific method, and then processing them into photovoltaic modules separately. This can fully utilize the raw materials of silicon wafers and reduce material waste. In addition, half-cell photovoltaic modules have better photoelectric conversion efficiency and lower temperature coefficient than full-cell photovoltaic modules, so they can provide higher power generation under partial light conditions.

[0048] With the continuous advancement of solar energy technology, the production cost of half-cell photovoltaic modules has gradually decreased, while its performance and reliability have also been further improved. Therefore, half-cell photovoltaic modules have become the first choice for many solar energy projects in the current market, especially in the construction of large-scale photovoltaic power stations.

[0049] Cutting a whole solar cell in half can reduce current density and resistance loss, thereby improving the power generation efficiency and reliability of photovoltaic modules. Furthermore, half-cell photovoltaic modules have better anti-shading effects and can maintain high power generation efficiency under shadow conditions. In addition, in the manufacturing process, half-cell technology helps reduce connection difficulty and improve production efficiency.

[0050] However, the manufacture of half-cell photovoltaic modules also generates some derivative problems. Specifically, the conventional method is to directly laser cut a whole solar cell that has been formed with multiple film layers to cut the whole solar cell into at least two split solar cells, such as two half-cells. Afterwards, a passivation layer is formed on the cut surface of the split solar cell.

[0051] See also Figure 1 and Figure 2 In this process, a continuously distributed passivation layer 6 is also formed on the edge area of ​​the light-facing surface 5 and the backlight surface of the split solar cell adjacent to the cut surface (see Figure 2 At this time, the color difference between the two areas with the passivation layer 6 and the area without the passivation layer on the light-facing side 5 (or the backlight side) of the split solar cell is relatively large (specifically, the normal area 7 without the continuously distributed passivation layer 6 is light blue, and the area with the continuously distributed passivation layer 6 is white). By comparison, it can be seen that the solar cell has a large visual difference and low aesthetics.

[0052] In order to solve the above technical problems, in a first aspect, an embodiment of the present invention provides a solar cell. Figure 3 and Figure 4The solar cell comprises a first surface 1 and a second surface opposite to each other, and a side surface connecting the first surface 1 and the second surface, wherein the side surface comprises a cut surface. The solar cell comprises: a first passivation layer 2 formed on the cut surface, and a plurality of second passivation layers 3 spaced apart and formed on edge regions adjacent to the cut surface in the first surface 1 and / or the second surface. It should be understood that both the edge region of the first surface 1 and the edge region of the second surface have a boundary line with the cut surface.

[0053] See also Figures 1 to 4 In the solar cell provided by the embodiment of the present invention, a plurality of second passivation layers 3 are distributed at intervals on the edge region, that is, the second passivation layer 3 formed on the first surface 1 and / or the second surface is discontinuous. Compared with the prior art, the continuously distributed passivation layer 6 formed on the edge region adjacent to the cut surface in the light-facing surface 5 and the backlight surface of the sliced ​​solar cell, when the area of ​​the edge region involved in the embodiment of the present invention and the prior art is completely equal or substantially equal or the edge region in the present invention is smaller than the edge region in the prior art, the proportion of the second passivation layer 3 formed in the present invention in the first surface 1 and / or the second surface is reduced. Based on this, the first surface 1 and / or the second surface presents a relatively uniform color visually, and the color difference of different regions of the first surface 1 and / or the second surface is reduced compared with the solar cell in the prior art, the visual difference of the solar cell is reduced, and the aesthetics of the solar cell is improved. Furthermore, the plurality of second passivation layers 3 distributed at intervals in the present invention can also reduce the influence on the surface refractive index of the first surface 1 and / or the second surface, and improve the PL brightness, thereby improving the cell efficiency of the solar cell. Furthermore, an electrode structure is formed on the first surface 1 and / or the second surface of the solar cell. In the prior art, the electrode structure closer to the edge of the solar cell is covered by the continuously distributed second passivation layer 3, which may affect the connection between the connecting parts such as welding ribbons and the electrode structure of the solar cell. However, since the multiple second passivation layers 3 in the embodiment of the present invention are distributed at intervals, the probability of the electrode structure close to the edge of the solar cell being completely covered can be reduced or eliminated, thereby improving the connection stability between the connecting parts such as welding ribbons and the electrode structure, so as to improve the quality of the photovoltaic module finally formed. In addition, since the first passivation layer 2 is formed on the cutting surface, the first passivation layer 2 can passivate the cutting surface, reduce the recombination rate of photogenerated carriers at the cutting surface, and improve the photoelectric conversion efficiency of the solar cell. It can be understood that the multiple second passivation layers distributed at intervals in the present application are not interconnected to form a whole in the edge area of ​​the first surface and / or the second surface, but there are no interconnected parts in the edge area of ​​the first surface and / or the second surface. For details, see Figure 3 and Figure 4There is no connected part between any two adjacent second passivation layers that are spaced apart, and any two adjacent second passivation layers that are spaced apart are in a completely separated state.

[0054] As a possible implementation, the solar cell may include a semiconductor substrate, a doped layer formed on the first surface or the second surface of the semiconductor substrate, and a first passivation layer and a second passivation layer formed on the semiconductor substrate and the doped layer. Of course, the solar cell may also include other film layer structures, which are not specifically limited here.

[0055] In an optional manner, the above-mentioned semiconductor substrate may be a substrate of a semiconductor material such as a silicon substrate, a germanium silicon substrate or a germanium substrate. In terms of conductivity type, the semiconductor substrate may be an intrinsic conductive substrate, an N-type conductive substrate or a P-type conductive substrate. Preferably, the semiconductor substrate is an N-type conductive substrate or a P-type conductive substrate. Compared with the intrinsic conductive substrate, the N-type conductive substrate or the P-type conductive substrate has a higher conductivity, which is beneficial to reduce the series resistance of the solar cell and improve the efficiency of the solar cell. In terms of structure, the first surface of the solar cell may be a velvet surface to improve the light trapping effect of the solar cell toward the light surface, thereby improving the utilization rate of the solar cell for light. Of course, the first surface of the solar cell may also be a flat polished surface. As for the second surface of the solar cell, it may be a polished surface or a velvet surface, which is not specifically limited here.

[0056] In terms of materials, the material of the doped layer may include any semiconductor material such as silicon, germanium silicon or germanium. In terms of the arrangement of the material, the crystalline phase of the doped layer may be amorphous, microcrystalline, nanocrystalline, single crystal or polycrystalline. Exemplarily, the doped layer may be composed of one or more of polycrystalline silicon, amorphous silicon, microcrystalline silicon and nanocrystalline silicon.

[0057] In terms of the number of film layers, the first passivation layer can be a single-layer structure or a stacked structure. The second passivation layer can be a single-layer structure or a stacked structure. In terms of materials, the material of the first passivation layer or the second passivation layer can include one or more of silicon oxide, aluminum oxide, titanium oxide, hafnium dioxide, gallium oxide, tantalum pentoxide, niobium pentoxide, silicon nitride, silicon carbonitride, aluminum nitride, titanium nitride, titanium nitride carbonitride, and amorphous silicon. The material of the first passivation layer and the material of the second passivation layer can be the same or different. In an embodiment of the present invention, the first passivation layer and the second passivation layer are both stacked structures. Exemplarily, the material of the first passivation layer includes an aluminum oxide passivation layer (or a silicon dioxide passivation layer) formed on the cutting surface, and a silicon nitride passivation layer formed on the aluminum oxide passivation layer (or a silicon dioxide passivation layer). The second passivation layer is similar and will not be described here.

[0058] In terms of distribution, see Figures 3 to 7 , multiple second passivation layers 3 are distributed in the edge area in an island shape. At this time, multiple second passivation layers 3 distributed in an island shape are conducive to the light passing through the side wall of the second passivation layer 3 to reflect more light to the texture structure between two spaced second passivation layers 3, thereby improving the light trapping effect of the first surface 1 and / or the second surface of the solar cell, increasing the light absorption rate, so as to improve the utilization rate of the first surface 1 and / or the second surface of the solar cell for light, thereby improving the photoelectric conversion efficiency of the solar cell.

[0059] From the perspective of shape, see Figures 3 to 7 Along the thickness direction of the solar cell, the plane shape of the second passivation layer 3 is a triangle, a quadrilateral, a pentagon or a closed figure composed of an arc and a line segment. In the embodiment of the present invention, the plane shape of the second passivation layer 3 is an irregular polygon.

[0060] As a possible implementation, see Figures 3 to 5 The second passivation layer 3 includes an end portion close to the first surface 1 and / or the central area of ​​the second surface, and the end boundaries of the plurality of second passivation layers 3 are wavy or sawtooth-shaped.

[0061] Exemplarily, the second passivation layer 3 located on the first surface 1 includes an end portion close to the central area of ​​the first surface 1, and the end boundaries of all the second passivation layers 3 are wavy or sawtooth-shaped. And / or, the second passivation layer 3 located on the second surface includes an end portion close to the central area of ​​the second surface, and the end boundaries of all the second passivation layers 3 are wavy or sawtooth-shaped. Alternatively, the second passivation layer 3 located on the first surface 1 includes an end portion close to the central area of ​​the first surface 1, and the end boundaries of two or more adjacent second passivation layers 3 are wavy or sawtooth-shaped. And / or, the second passivation layer 3 located on the second surface includes an end portion close to the central area of ​​the second surface, and the end boundaries of two or more adjacent second passivation layers 3 are wavy or sawtooth-shaped.

[0062] When the above technical solution is adopted, compared with the case where the end boundaries of the plurality of second passivation layers are linear, the proportion of the second passivation layer in the first surface and / or the second surface can be further reduced. Based on this, the visual difference of the solar cell can be further reduced and the aesthetics of the solar cell can be improved.

[0063] As a possible implementation, see Figure 6 The side surface further includes a non-cut side surface 4 adjacent to the cut surface, and a plurality of second passivation layers 3 distributed at intervals are also formed on edge regions of the non-cut side surface 4 adjacent to the cut surface.

[0064] When the above technical solution is adopted, compared with the prior art in which a continuously distributed passivation layer is formed on the non-cut side surface, the multiple second passivation layers 3 distributed at intervals in the embodiment of the present invention can also reduce the impact on the surface refractive index of the non-cut side surface 4, further improving the cell efficiency of the solar cell. Furthermore, the multiple second passivation layers 3 distributed at intervals are conducive to the light passing through its side wall to reflect more light to the texture structure between two second passivation layers 3 distributed at intervals, thereby improving the light trapping effect of the non-cut side surface 4 of the solar cell, increasing the light absorption rate, so as to improve the utilization rate of the non-cut side surface 4 of the solar cell for light, thereby improving the photoelectric conversion efficiency of the solar cell.

[0065] In combination with the above description, a plurality of second passivation layers are distributed in an island shape in an edge region of the non-cut side surface adjacent to the cut surface, and the planar shape of the second passivation layer is an irregular polygon.

[0066] According to the foregoing description, the solar cell includes a first surface 1 and a second surface relative to each other. When the first surface 1 is the light-facing surface and the second surface is the backlight surface, in order to better utilize the light, the incident angle of the first surface 1 of the solar cell is as close to 0 as possible. However, this will cause the incident light on the side surface to have a large incident angle on the side surface, for example, close to 90°, which will result in a very low utilization rate of the light on the side surface. In the embodiment of the present invention, the shape of the second passivation layer 3 is a polygonal irregular shape and is distributed in an isolated island shape. This is beneficial to improve the utilization rate of light on the non-cut side surface 4 adjacent to the cut surface in the solar cell. For example, the attached Figure 6 After the incident light L1 and L2 pass through the second passivation layer 3, more light can be reflected onto the texture structure between two spaced-apart second passivation layers 3, thereby improving the light utilization rate of the non-cut side surface 4 adjacent to the cut surface in the solar cell.

[0067] In an optional manner, assuming that the area of ​​the edge region in the present application is equal to the area of ​​the edge region in the prior art, in the edge region in the present application, the ratio of the total area of ​​the second passivation layer to the area of ​​the edge region is less than or equal to 1%. For example, the ratio may be 1%, 0.9%, 0.8%, 0.7%, 0.6%, 0.5%, 0.4%, 0.3%, 0.2%, 0.1%, 0.05%, etc.

[0068] Compared with the prior art, the area of ​​the second passivation layer formed on the first surface and / or the second surface and / or the non-cut side surface adjacent to the cut surface in the embodiment of the present invention is greatly reduced. At this time, not only can the aesthetics, surface refractive index, and PL brightness of the solar cell be significantly improved, thereby improving the cell efficiency of the solar cell; at the same time, it will not affect the connection between the connecting parts such as the welding ribbon and the electrode structure, thereby improving the quality of the final component formed.

[0069] As a possible implementation, see Figure 5 The plurality of second passivation layers 3 include at least one second passivation layer 3 spaced apart from the first passivation layer 2 , and the spacing between the first passivation layer 2 and the second passivation layer 3 is not specifically limited herein.

[0070] As a possible implementation, see Figure 3 and Figure 5 , along the vertical direction from the edge area of ​​the first surface 1 to the central area of ​​the first surface 1, the width W of the second passivation layer 3 on the first surface 1 is greater than or equal to 0 mm and less than or equal to 1 mm. For example, the width W of the second passivation layer 3 can be 0 mm, 0.05 mm, 0.1 mm, 0.3 mm, 0.5 mm, 0.7 mm, 0.8 mm, 0.85 mm, 0.9 mm or 1 mm, etc.

[0071] Preferably, along the vertical direction from the edge area of ​​the first surface 1 to the central area of ​​the first surface 1, the width W of the second passivation layer 3 on the first surface 1 is greater than or equal to 0 mm and less than or equal to 20 μm. For example, the width W of the second passivation layer 3 can be 0 mm, 1 μm, 3 μm, 5 μm, 8 μm, 10 μm, 12 μm, 13 μm, 15 μm, 17 μm, 18 μm or 20 μm, etc. At this time, not only can the color difference between different areas of the first surface be completely avoided, but also the visual difference of the solar cell can be further reduced. At the same time, the probability of the electrode structure near the edge of the solar cell in the first surface being completely covered can be eliminated, ensuring that the connection between the connecting parts such as the welding strip and the electrode structure will not be affected, thereby improving the quality of the final component.

[0072] For example, see Figure 7 , along the vertical direction from the edge area of ​​the first surface 1 to the central area of ​​the first surface 1 , the width W of the second passivation layer 3 on the first surface 1 is 3.473 μm.

[0073] In the vertical direction from the edge area of ​​the second surface to the center area of ​​the second surface, the width of the second passivation layer on the second surface is greater than or equal to 0 mm and less than or equal to 1 mm. For example, the width of the second passivation layer can be 0 mm, 0.05 mm, 0.1 mm, 0.3 mm, 0.5 mm, 0.7 mm, 0.8 mm, 0.85 mm, 0.9 mm or 1 mm, etc.

[0074] Preferably, along the vertical direction from the edge area of ​​the second surface to the central area of ​​the second surface, the width of the second passivation layer on the second surface is greater than or equal to 0 mm and less than or equal to 20 μm. For example, the width W of the second passivation layer 3 can be 0 mm, 1 μm, 3 μm, 5 μm, 8 μm, 10 μm, 12 μm, 13 μm, 15 μm, 17 μm, 18 μm or 20 μm, etc. At this time, not only can the color difference between different areas of the second surface be completely avoided, but also the visual difference of the solar cell can be further reduced. At the same time, the probability of the electrode structure near the edge of the solar cell in the second surface being completely covered can be eliminated, ensuring that the connection between the connecting parts such as the welding strip and the electrode structure will not be affected, thereby improving the quality of the final component.

[0075] In summary, by adopting the above technical solution, the aesthetics, surface refractive index, and PL brightness of solar cells can be significantly improved, thereby improving the cell efficiency of solar cells. Furthermore, when the width W of the second passivation layer 3 on the first surface 1 is greater than or equal to 0 mm and less than or equal to 20 μm in the vertical direction from the edge area of ​​the first surface 1 to the center area of ​​the first surface 1; and the width of the second passivation layer on the second surface is greater than or equal to 0 mm and less than or equal to 20 μm in the vertical direction from the edge area of ​​the second surface to the center area of ​​the second surface, not only can the solar cell have no visual difference, but also will not affect the connection between the connecting parts such as the welding strip and the electrode structure, thereby improving the quality of the final component.

[0076] As a possible implementation, see Figure 5 and Figure 6 , the thickness of the first passivation layer is greater than the thickness of the second passivation layer.

[0077] When the above technical solution is adopted, the passivation effect of the first passivation layer on the cut surface can be improved, the recombination rate of photogenerated carriers at the cut surface can be further reduced, and the photoelectric conversion efficiency of the solar cell can be improved. Furthermore, since the thickness of the second passivation layer is relatively thin, it can not only reduce the influence of the second passivation layer on the surface refractive index and improve the cell efficiency of the solar cell, but also reduce the visual difference of the solar cell and improve the aesthetics of the solar cell.

[0078] In an optional manner, the thickness of the first passivation layer is greater than or equal to 10 nm and less than or equal to 300 nm. Exemplarily, the thickness of the first passivation layer can be 10 nm, 30 nm, 50 nm, 85 nm, 100 nm, 130 nm, 150 nm, 170 nm, 190 nm, 200 nm, 220 nm, 250 nm, 280 nm, 290 nm or 300 nm, etc.

[0079] In a second aspect, an embodiment of the present invention further provides a photovoltaic module. The photovoltaic module comprises: a battery string and an encapsulation layer. The battery string is formed by connecting a plurality of solar cells as described in the above technical solution, and the encapsulation layer is used to cover the surface of the battery string.

[0080] Another aspect of the present invention is to heat-treat the formed passivation layer, which can effectively improve the passivation performance of the passivation layer. The improvement of the passivation performance after the heat treatment does not depend on the distribution position and morphology of the passivation layer. Whether the passivation layer on the first surface or the second surface is distributed at intervals or continuously, the passivation performance can be improved by heat-treating it. In particular, for the sidewall passivation layer formed by a low-temperature process and the passivation layer on the first surface and the second surface, the heat treatment can improve its passivation performance more significantly. The heat treatment method can be in various forms, such as laser annealing, heat treatment in a relatively closed area with a temperature field. The heat treatment temperature is, for example, preferably greater than 200 degrees Celsius. Exemplarily, the above-mentioned passivation layer can be the first passivation layer and / or the second passivation layer in the present application.

[0081] The beneficial effects of the photovoltaic module provided by the embodiment of the present invention are the same as the beneficial effects of the solar cell described in the above technical solution, and will not be described in detail here.

[0082] In a third aspect, an embodiment of the present invention further provides a method for preparing a solar cell. The method for preparing a solar cell comprises:

[0083] First, a semiconductor substrate is provided;

[0084] Exemplarily, the semiconductor substrate may be a substrate made of semiconductor materials such as a silicon substrate, a silicon germanium substrate or a germanium substrate. In terms of conductivity type, the semiconductor substrate may be an intrinsic conductive substrate, an N-type conductive substrate or a P-type conductive substrate. Preferably, the semiconductor substrate is an N-type conductive substrate or a P-type conductive substrate. Compared with the intrinsic conductive substrate, the N-type conductive substrate or the P-type conductive substrate has a higher conductivity, which is beneficial to reduce the series resistance of the solar cell and improve the efficiency of the solar cell. In terms of structure, the specific structure of the semiconductor substrate may be set according to the actual application scenario. For example: the semiconductor substrate may be a semiconductor substrate on which no film layer is formed, and both the backlight surface and the light-receiving surface are polished surfaces. Alternatively, the semiconductor substrate may be a semiconductor substrate on which no film layer is formed, and the light-receiving surface is a velvet surface. Among them, compared with the polished surface, because the velvet structure has a good light trapping effect, when the light-receiving surface of the semiconductor substrate is a velvet surface, more light can be refracted from the light-receiving surface into the semiconductor substrate, thereby facilitating the improvement of the photoelectric conversion efficiency of the solar cell.

[0085] In the actual application process, the semiconductor substrate is first polished and cleaned. As for the specific steps of polishing and cleaning, reference can be made to the prior art and no specific limitation is made here.

[0086] Next, the semiconductor substrate is divided into at least two semiconductor substrate slices; the semiconductor substrate slices include a first surface and a second surface opposite to each other, and a side surface connecting the first surface and the second surface; the side surface includes a cutting surface;

[0087] For example, a laser process or other non-destructive cutting methods may be used to separate the semiconductor substrate into at least two semiconductor substrate slices.

[0088] Next, the cut surface of the sliced ​​semiconductor substrate is cleaned for damage, and the laser damage layer generated by laser cutting can be removed to reduce lattice defects.

[0089] Exemplarily, in a chain cleaning machine, the sliced ​​semiconductor substrate is placed in a HF and HNO3 tank, and a roller-liquid method or a water-floating method is used to remove part of the silicon slag and silicon oxide on the cut surface of the sliced ​​semiconductor substrate. Since the cut surface is not protected by the phosphorus-silicon glass layer, the concentration of HF and HNO3 is increased to increase the corrosion of the cut surface, thereby increasing the cleaning of the cut surface, making the cut surface smoother than the cut surface in the prior art, and making the cleaning effect of the cut surface similar to the cleaning effect of other surfaces of the sliced ​​semiconductor substrate. Then, when passing through the tank cleaning machine, the ratio of alkali texturing and additives is adjusted, and the cut surface is texturized and corroded, so that the effects of texturing on each surface of the sliced ​​semiconductor substrate are similar, so that after the first passivation layer is formed on the sliced ​​semiconductor substrate later, the passivation effect of the solar cell is improved.

[0090] Next, a first passivation layer is formed on the cut surface.

[0091] Exemplarily, the sliced ​​solar cells are stacked and loaded into a tooling box with four closed sides and two open sides, and then one open surface in the tooling box is closed to ensure that only the cut surface is exposed outside the tooling box. Preferably, a first passivation layer is formed on the cut surface by PVD equipment under a vacuum environment by electron beam, resistance thermal evaporation, magnetron sputtering, etc. At this time, the passivation effect of the solar cell can be improved to improve the photoelectric conversion efficiency of the solar cell. In addition, since the first passivation layer is formed on the cut surface of the sliced ​​semiconductor substrate after cleaning, under the action of the first passivation layer, the surface dangling bonds generated by the cut surface of the sliced ​​semiconductor substrate being directly exposed to the air can be saturated. Based on this, the minority carrier lifetime of the cut surface can be increased to reduce the recombination current, thereby improving the conversion efficiency of the solar cell and the component power.

[0092] In an optional manner, the first passivation layer includes a multilayer structure stacked, such as a laminated film of aluminum oxide and silicon nitride, and the first passivation layer is located on the cut surface of the semiconductor substrate to improve the protection of the cut surface. Aluminum oxide has good insulation and chemical stability, and can effectively prevent charge recombination. The silicon nitride passivation layer can play an anti-reflection role, which is conducive to allowing more light to be refracted from the cut surface into the semiconductor substrate, so as to further improve the utilization rate of light by the solar cell. Furthermore, silicon nitride has high light transmittance and good passivation effect, and effective passivation can be achieved by forming a layer of silicon nitride passivation layer on the surface of the solar cell.

[0093] By controlling the state of the stack of the sliced ​​solar cells in the tooling box, such as the clamping state, or the spacing between the deposition source and the cell stack, a plurality of second passivation layers distributed at intervals are formed on the edge region adjacent to the cut surface in the first surface and / or the second surface during the process of forming the first passivation layer. For a detailed description of the second passivation layer, please refer to the first aspect and will not be repeated here.

[0094] The beneficial effects of the method for preparing a solar cell provided by the embodiment of the present invention are the same as the beneficial effects of the solar cell described in the above technical solution, and will not be described in detail here.

[0095] In one implementation, the temperature for forming the first passivation layer and the second passivation layer is less than or equal to 100°C.

[0096] For the convenience of subsequent description, the first passivation layer and the second passivation layer are collectively referred to as passivation layers. Compared with the high temperature process used in the prior art to form the passivation layer, the temperature used in the present invention when forming the passivation layer is lower than the temperature used in the prior art. At this time, the damage to the film layer already formed on the semiconductor substrate can be reduced or avoided during the formation of the passivation layer. For example, when the solar cell is a BC (i.e., back contact cell) type solar cell, it is possible to avoid damaging the surface protection film already formed on the semiconductor substrate to avoid releasing organic matter, thereby avoiding damaging the edge passivation effect, so as to ensure the yield and component power of the solar cell. Exemplarily, the photovoltaic module made of solar cells obtained by the preparation method provided in an embodiment of the present invention has a component power increased by more than 3W compared to the 72-piece version.

[0097] Optionally, the first passivation layer and / or the second passivation layer is subjected to a heat treatment, such as laser annealing.

[0098] Another aspect of the present invention is to heat-treat the formed passivation layer, which can effectively improve the passivation performance of the passivation layer. The improvement of the passivation performance after the heat treatment does not depend on the distribution position and morphology of the passivation layer. Whether the passivation layer on the first surface or the second surface is distributed at intervals or continuously, the passivation performance can be improved by heat-treating it. In particular, for the sidewall passivation layer formed by a low-temperature process and the passivation layer on the first surface and the second surface, the heat treatment can improve its passivation performance more significantly. The heat treatment method can be in various forms, such as laser annealing, heat treatment in a relatively closed area with a temperature field. The heat treatment temperature is, for example, preferably greater than 200 degrees Celsius. Exemplarily, the above-mentioned passivation layer can be the first passivation layer and / or the second passivation layer in the present application.

[0099] In the description of the above embodiments, specific features, structures, materials or characteristics may be combined in any one or more embodiments or examples in a suitable manner. The above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention shall be based on the protection scope of the claims.

Claims

1. A solar cell, characterized in that: The solar cell comprises a first surface and a second surface opposite to each other, and a side surface connecting the first surface and the second surface; the side surface comprises a cutting surface; The solar cell comprises: forming a first passivation layer on the cut surface; And a plurality of second passivation layers distributed at intervals are formed on edge regions of the first surface and / or the second surface adjacent to the cutting surface.

2. The solar cell according to claim 1, characterized in that A plurality of the second passivation layers are distributed in the edge region in an island shape.

3. The solar cell according to claim 1, characterized in that Along the thickness direction of the solar cell, the plane shape of the second passivation layer is a triangle, a quadrilateral, a pentagon, or a closed figure composed of an arc and a line segment.

4. The solar cell according to claim 1, characterized in that The second passivation layer includes an end portion close to the first surface and / or a central area of ​​the second surface, and the end portions of the plurality of second passivation layers are wavy or sawtooth-shaped.

5. The solar cell according to claim 1, characterized in that: The side surface also includes a non-cutting side surface adjacent to the cutting surface; A plurality of second passivation layers distributed at intervals are also formed on an edge region of the non-cut side surface adjacent to the cut surface.

6. The solar cell according to claim 1, characterized in that The plurality of second passivation layers include at least one second passivation layer spaced apart from the first passivation layer.

7. The solar cell according to claim 1, characterized in that Along the vertical direction from the edge area of ​​the first surface to the central area of ​​the first surface, the width of the second passivation layer located on the first surface is greater than or equal to 0 mm and less than or equal to 1 mm; And / or, along a vertical direction from an edge area of ​​the second surface to a central area of ​​the second surface, a width of the second passivation layer on the second surface is greater than or equal to 0 mm and less than or equal to 1 mm.

8. The solar cell according to claim 1, characterized in that The thickness of the first passivation layer is greater than the thickness of the second passivation layer.

9. The solar cell according to claim 1, characterized in that: The thickness of the first passivation layer is greater than or equal to 10 nm and less than or equal to 300 nm.

10. A photovoltaic module, characterized in that: The photovoltaic module comprises: A battery string, wherein the battery string is formed by connecting a plurality of solar cells according to any one of claims 1 to 9; The encapsulation layer is used to cover the surface of the battery string.

11. A method for preparing a solar cell, comprising: Providing a semiconductor substrate; dividing the semiconductor substrate into at least two semiconductor substrate slices; The sliced ​​semiconductor substrate comprises a first surface and a second surface opposite to each other, and a side surface connecting the first surface and the second surface; the side surface comprises a cutting surface; forming a first passivation layer on the cut surface; A plurality of second passivation layers distributed at intervals are formed on edge regions of the first surface and / or the second surface adjacent to the cutting surface.

12. The method for preparing a solar cell according to claim 11, characterized in that: The temperature for forming the first passivation layer and the second passivation layer is less than or equal to 100° C.

13. The method for preparing a solar cell according to claim 11 or 12, characterized in that: The method further includes performing a heat treatment on the first passivation layer and / or the second passivation layer.

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