Solar cell and photovoltaic module

Abstract

The invention provides a solar cell and a photovoltaic module, and relates to the technical field of photovoltaics. The solar cell includes: a silicon substrate; the transmission layer and the passivation anti-reflection layer are stacked on at least one of the first surface and the second surface of the silicon substrate; in the direction of the thickness of the silicon substrate, the transmission layer is located between the silicon substrate and the passivation anti-reflection layer; the passivation anti-reflection layer is provided with a plurality of openings; a region corresponding to the opening in one side, deviating from the silicon substrate, of the transmission layer is a contact region; a ridge line is arranged in at least one contact area; the electrode is arranged on the side, away from the silicon substrate, of the passivation anti-reflection layer, and the electrode penetrates through the opening to be in contact with the transmission layer. The solar cell improves the binding force between the electrode and the transmission layer, improves the binding force or contact effect between the electrode and the transmission layer, improves the current collection and conduction effects, and improves the performance of the solar cell.

Description

Technical Field

[0001] The invention relates to the field of photovoltaic technology, in particular to a solar cell and a photovoltaic module. Background Art

[0002] Solar cells are devices that directly convert light energy into electrical energy through the photoelectric effect. Since solar cells are mainly used as clean energy, they have broad application prospects.

[0003] The electrodes in solar cells are mainly used to collect and conduct current. The bonding force or contact effect between the electrodes and the transmission layer has a great influence on the current collection and conduction effect.

[0004] In existing solar cells, in order to ensure the film quality of the transmission layer, the film is usually relatively uniform, but the bonding force between the electrode and the contact area in the transmission layer is insufficient, the reliability is poor, and the performance of the solar cell is affected. Summary of the invention

[0005] The present invention provides a solar cell and a photovoltaic module, aiming to solve the problems of insufficient bonding force and poor reliability of the contact area between the electrode and the transmission layer in the existing solar cell.

[0006] A first aspect of the present invention provides a solar cell, comprising:

[0007] A silicon substrate; in the direction of the thickness of the silicon substrate, the silicon substrate has a first surface and a second surface opposite to each other;

[0008] A transmission layer and a passivation anti-reflection layer are stacked on at least one of the first surface and the second surface; in the direction of the thickness of the silicon substrate, the transmission layer is located between the silicon substrate and the passivation anti-reflection layer; the passivation anti-reflection layer has a plurality of openings; the area corresponding to the opening on the side of the transmission layer away from the silicon substrate is a contact area; at least one of the contact areas has an ridge.

[0009] An electrode is arranged on a side of the passivation anti-reflection layer away from the silicon substrate, and the electrode passes through the opening to contact the transmission layer.

[0010] In the present application, in the contact area, the electrode contacts the transmission layer to achieve current collection and conduction. The passivation anti-reflection layer has a plurality of openings, and the area corresponding to the openings on the side of the transmission layer away from the silicon substrate is the contact area. The contact area is the position where the electrode and the transmission layer contact. At least one contact area has a ridge, and the surface of the ridge is relatively rough. On the one hand, the contact area has a large specific surface area, thereby increasing the bonding area with the electrode, improving the contact performance of the electrode and the transmission layer, reducing the contact resistance, and improving the collection and conduction effect of current or carriers, thereby improving the performance of the solar cell; on the other hand, the contact area is rougher, and the contact and bonding with the electrode is tighter, the bonding force is greater, and the subsequent process is prevented from pulling off, and the reliability is strong.

[0011] Optionally, at least one of the contact areas has a tower base structure, and the ridge line includes: the side length of the tower base structure.

[0012] Optionally, there is at least one hole in the contact area at the location of the ridge line.

[0013] Optionally, the edge of the hole has an annular protrusion.

[0014] Optionally, the density of holes at the ridges is greater than the density of holes in other regions, and / or the density of protrusions at the ridges is greater than the density of protrusions in other regions.

[0015] Optionally, at least some of the holes at the position where the ridge line is located are interconnected, and / or the protrusion at the ridge line extends into a strip along the ridge line.

[0016] Optionally, there are multiple holes in the contact area; the contact area includes: a central area and an edge area surrounding the central area; for one of the contact areas: the size of the holes in the central area is larger than the size of the holes in the edge area.

[0017] Optionally, an area outside the contact area on a side of the transmission layer facing away from the silicon substrate is a non-contact area;

[0018] The roughness of the contact area is greater than the roughness of the non-contact area.

[0019] Optionally, the transmission layer includes a plurality of transmission areas, and on one of the transmission areas, there is a gap between the contact area and an edge of the transmission area.

[0020] Optionally, in the extension direction of the transmission zone, the size of the interval is 50 μm to 200 μm.

[0021] Optional,

[0022] The ratio of the maximum dimension of one of the openings to the side length of one of the tower base structures is 0.5 to 5.

[0023] Optionally, the transmission layer includes: a first transmission layer and a second transmission layer, and the first transmission layer and the second transmission layer have different doping types;

[0024] The side length of the tower base structure in the first transmission layer is smaller than the side length of the tower base structure in the second transmission layer;

[0025] and / or,

[0026] The depth of the tower base structure in the first transmission layer is greater than the depth of the tower base structure in the second transmission layer.

[0027] Optionally, the length of one of the ridge lines is 5um to 40um, and / or the side length of one of the tower base structures is 5um to 40um.

[0028] Optionally, the height and width of the protrusion are both less than or equal to 0.5 μm; the direction of the height is parallel to the direction of the thickness of the silicon substrate, and the width is the maximum dimension of the protrusion on a plane perpendicular to the direction of the height.

[0029] Optionally, the transmission layer includes a polysilicon doped layer; the polysilicon doped layer has a polysilicon region and an amorphous silicon region, and the amorphous silicon region is located on the side of the polysilicon doped layer away from the silicon substrate; the amorphous silicon region is located between the passivation anti-reflection layer and the polysilicon region, and is located at the position of the opening.

[0030] Optionally, the thickness of the amorphous silicon at the ridge line is greater than the thickness of the amorphous silicon in other areas.

[0031] Optionally, the electrode includes a stacked seed layer and a non-fire-through slurry layer.

[0032] A second aspect of the present invention provides a photovoltaic assembly, comprising: a plurality of any of the aforementioned solar cells.

[0033] The above-mentioned solar cells and photovoltaic modules have the same or similar beneficial effects, which will not be described again here to avoid repetition. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments of the present invention will be briefly introduced below. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative labor.

[0035] Figures 1 to 3 Schematic diagrams of partial structures of three solar cells in embodiments of the present invention are shown;

[0036] Figures 4 to 9 Schematic diagrams of partial SEM structures of four solar cells in the embodiments of the present invention are shown.

[0037] Description of the accompanying drawings:

[0038] 1-silicon substrate, 11-ridges, 12-tower base structure, 2-polysilicon doping layer, 3-tunneling oxide layer, 4-electrode, 41-seed layer, 42-slurry layer, 5-passivation anti-reflection layer, 6-opening, 71-contact area, 72-non-contact area, 73-transmission area of ​​the first transmission layer, 74-transmission area of ​​the second transmission layer, 8-isolation area, 21-amorphous silicon area, 22-micron crystals and / or nano crystals, 23-polysilicon area, 24-protrusions, 9-holes. DETAILED DESCRIPTION

[0039] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0040] In the relevant technology of solar cells, in order to reduce the cost of high-temperature silver paste, it is usually adopted to open at the interface of the passivation anti-reflection layer such as silicon nitride, remove part of the passivation anti-reflection layer, form an exposed transmission layer contact window, and use a low-temperature metallization process to make electrodes, such as using low-temperature paste instead of high-temperature silver paste, or using electroplating process to form electrodes. On the one hand, the bonding force between the electrode and the transmission layer formed by the current low-temperature metallization process is lower than the bonding force provided by the fusion crystal formed by the melting of the glass body inside the silver paste and the silicon interface in the manufacture of high-temperature silver paste. On the other hand, in order to ensure the film quality of the transmission layer, the transmission layer film is usually more uniform, and the bonding force of the contact area between the electrode and the transmission layer is poor. The above factors will lead to a higher risk of the electrode detaching from the transmission layer, reducing the structural reliability of the solar cell.

[0041] In order to solve the above technical problems, the present invention provides a solar cell. In terms of the type of cell, the solar cell provided in the embodiment of the present application includes but is not limited to any of the following photovoltaic cells that can convert light energy into electrical energy. For example, the solar cell provided in the embodiment of the present application can be any of the following solar cells: a tunneling oxide passivated contact cell (Topcon), a doped polycrystalline silicon full back contact cell (TBC), a composite passivated back contact cell (HPBC), a double-sided hybrid cell, etc. Figure 1 , the solar cell includes: a silicon substrate 1, a transmission layer, an electrode 4 and a passivation anti-reflection layer 5. In the thickness direction Q of the silicon substrate 1, the silicon substrate 1 has a first surface and a second surface opposite to each other. During the operation of the solar cell, the surface of the silicon substrate 1 that mainly receives light is its light-facing surface. In the thickness direction Q of the silicon substrate 1, the backlight surface and the light-facing surface are opposite to each other. Among the first surface and the second surface here, one surface can be the backlight surface of the silicon substrate 1, and the other surface can be the light-facing surface of the silicon substrate 1. For example, Figure 1 The upper surface of the silicon substrate is the backlight surface of the silicon substrate.

[0042] The transmission layer and the passivation anti-reflection layer 5 are stacked on at least one of the first surface and the second surface of the silicon substrate 1. The transmission layer here may include a P-type transmission layer and / or an N-type transmission layer. The P-type transmission layer and the N-type transmission layer may both be located on the backlight side of the silicon substrate 1, in which case it is a back contact battery, or either the P-type transmission layer or the N-type transmission layer is located on the backlight side of the silicon substrate 1, and the other is located on the light-facing side of the silicon substrate 1, in which case it is a double-sided contact battery. There is no limitation on the specific material of the transmission layer. For example, refer to Figure 1 The transmission layer may include a polysilicon doped layer 2, a polysilicon region containing polysilicon in the polysilicon doped layer 2, and a thickness of the polysilicon doped layer 2 may be 50nm to 250nm. The direction of the thickness of the polysilicon doped layer 2 and the directions of the thickness of other structures mentioned in the present application are parallel to the thickness direction Q of the silicon substrate 1 unless otherwise specified. Whether the transmission layer includes other layers is not specifically limited. Figure 1 , 2 in the attached drawings refers to the polysilicon doping layer. Figure 1 The N-type polysilicon doping layer and the P-type polysilicon doping layer may be included.

[0043] In the direction Q where the thickness of the silicon substrate 1 is located, the transmission layer is located between the silicon substrate 1 and the passivation anti-reflection layer 5. Figure 2 and Figure 3, the passivation anti-reflection layer 5 has a plurality of openings 6 at local positions, and the number of openings 6 in the passivation anti-reflection layer 5 is not specifically limited. The openings 6 in the present application may be other shapes such as circular, square or elliptical. Since the passivation anti-reflection layer has insulating properties, an opening area must be set, and the opening leaks out at least part of the transmission layer. In this way, electrodes can be formed at the openings by a low-temperature metallization process, which can reduce the cost of metallization. After the passivation anti-reflection layer 5 is provided with the openings 6, the area corresponding to the openings 6 on the side of the transmission layer facing away from the silicon substrate 1 will be exposed, refer to Figures 4 to 7 The area corresponding to the opening 6 in the side of the transmission layer away from the silicon substrate 1 is the position where the transmission layer and the electrode contact each other, that is, the area corresponding to the opening 6 in the side of the transmission layer away from the silicon substrate 1 is the contact area 71. SEM image refers to scanning electron microscope image.

[0044] In the present application, at least one contact region 71 has an edge line 11 (shown by a continuously extending line segment in a wire frame marked 11 in the figure), the passivation anti-reflection layer 5 has a plurality of openings 6, and the area corresponding to the opening 6 on the side of the transmission layer away from the silicon substrate 1 is the contact region 71, and the contact region 71 is the position where the electrode 4 and the transmission layer contact, and at least one contact region 71 has an edge line 11. Based on this, by adopting this method, an electrode can be formed at the opening 6 by a low-temperature metallization process, which can reduce the cost of the metallization process. In addition, compared with the prior art in which the electrode is formed on a relatively flat contact area, in the present application, at least one contact area has ridges, and the surface of the ridges 11 is relatively rough. On the one hand, compared with the contact area without ridges, the contact area with ridges has a larger specific surface area, thereby increasing the contact area between the transmission layer and the electrode, improving the contact performance between the electrode 4 and the transmission layer, and reducing the contact resistance, thereby improving the collection and conduction effect of current or carriers, and further improving the performance of the solar cell; on the other hand, the contact area with ridges is rougher, so that the contact bonding between the transmission layer and the electrode is tighter, which improves the connection strength and bonding force between the two, can effectively prevent subsequent process pulling off, and avoid the risk of the electrode falling off from the contact area, thereby improving the structural reliability of the solar cell.

[0045] It should be noted that the ridge here refers to a raised part with a certain regularity on the surface, and the raised part has a greater roughness than other surface areas. The ridge can be straight and / or curved, and the contact area can also include a regular or irregular texture structure composed of at least one ridge, and the texture structure has concave and convex changes at the ridge. The ridge here can be: the ridge in the tower base structure of the polished structure on the surface of the silicon substrate, at least partially conforming to the shape of the side of the transmission layer away from the silicon substrate; or, the ridge here can be: the ridge in the pyramid structure of the velvet structure on the surface of the silicon substrate, at least partially conforming to the shape of the side of the transmission layer away from the silicon substrate, and no specific limitation is made to this. It should be noted that the solar cell also includes: an electrode 4, and the electrode 4 here can be an N-type electrode or a P-type electrode. The electrode 4 is arranged on the side of the passivation anti-reflection layer away from the silicon substrate, and the electrode 4 contacts the transmission layer through the opening 6. The electrode 4 can be a collector grid line, or it can be a whole electrode structure containing a collector grid line, and no limitation is made to this. The electrode 4 can be a whole layer structure. Optional, see Figure 1 The electrode 4 is a multilayer structure, and the electrode 4 may include a seed layer 41 and a non-burn-through paste layer 42, indicating that the electrode is formed at the opening by a low-temperature metallization process, which can reduce the cost of metallization. The paste layer 42 here can be made of base metal, etc., which can reduce the cost of the solar cell.

[0046] It should be noted that the base metal here mainly refers to: does not contain silver, or contains a very small amount of silver. For example, the slurry layer here may include: a copper slurry layer, an aluminum slurry layer, or a slurry layer with a mass content of precious metals less than 50%, and the precious metal here may include silver. For example, the slurry layer here may be a silver-clad copper slurry layer, etc.

[0047] The seed layer 41 may contain metal elements, and the metal elements may be selected from at least one of titanium (Ti), tungsten (W), chromium (Cr), nickel (Ni), cobalt (Co), molybdenum (Mo), tin (Sn), lead (Pb), palladium (Pd), copper (Cu), niobium (Nb), ruthenium (Ru), indium (In), zinc (Zn), tantalum (Ta), and vanadium (V). Specifically, the material of the seed layer 41 is selected from the above materials, and the resistance of the above materials, the barrier properties of the metal elements in the slurry layer 42, and other properties are more suitable for the seed layer. In particular, the material of the seed layer 41 is selected from nickel and / or zinc. On the first hand, nickel and zinc both have good contact properties; on the second hand, nickel and zinc basically do not penetrate into the silicon substrate, and the composite is less; on the third hand, nickel and zinc have a good barrier effect on the metal in the slurry layer 42 on the side away from the silicon substrate, which can prevent the metal in the slurry layer 42 from penetrating into the silicon substrate, reducing the composite. It should be noted that x in the above chemical formula is a number greater than 0.

[0048] The slurry layer 42 may contain base metals. Compared with solar cells using silver paste, the present application may perform metal plating, etc. For example, the cost of solar cells may be reduced by using nickel, copper, and tin metals with mature technology and low price instead of silver paste. For another example, the seed layer 41 may contain nickel, and the slurry layer may contain copper. Nickel has good contact properties, and nickel basically does not penetrate into the silicon substrate, and there is less recombination. In addition, nickel has a good barrier effect on the copper and other metals in the slurry layer 42 on the side away from the silicon substrate, which can prevent the copper and other metals in the slurry layer 42 from penetrating into the silicon substrate, reducing recombination and reducing costs. The solar cell in the present application can achieve good contact performance between the metal and the silicon substrate under low temperature conditions (below 300°C, such as about 200°C), without the need for high-temperature furnace sintering, and the heat effect brought into the solar cell is very small.

[0049] The passivation anti-reflection layer 5 mentioned in the present application can provide a good passivation anti-reflection effect, and its specific material is not limited. For example, the passivation anti-reflection layer 5 may include an aluminum oxide layer and a silicon nitride layer stacked, wherein the aluminum oxide layer is closer to the silicon substrate, the thickness of the aluminum oxide layer may be 4nm to 10nm, and the thickness of the silicon nitride layer may be 50nm to 150nm.

[0050] In one embodiment, referring to Figures 5 to 7 , at least one contact area 71 has a tower base structure 12 ( Figure 5 The outline or structure in the frame marked with 12 is roughly square, and the ridge 11 includes the side length of the tower base structure 12. The tower base structure 12 is a polished structure or an attached structure on the polished surface, which means that the area on the surface of the silicon substrate 1 where the transmission layer is set is a polished surface or relatively flat, and the quality of the film layers such as the transmission layer and the passivation anti-reflection layer 5 formed thereon is good, and good passivation effects can be achieved. At the same time, the surface of the ridge 11 is relatively rough. On the one hand, compared with the contact area without ridges, the contact area with ridges has a larger specific surface area, thereby increasing the bonding area between the transmission layer and the electrode, improving the contact performance between the electrode 4 and the transmission layer, and reducing the contact resistance, thereby improving the collection and conduction effect of current or carriers, and thus improving the performance of the solar cell; on the other hand, the contact area with ridges is rougher, so that the contact bonding between the transmission layer and the electrode is tighter, which improves the connection strength and bonding force between the two, prevents subsequent processes from pulling off, and improves the structural reliability of the solar cell.

[0051] It should be noted that the tower base structure 12 in at least one contact area 71 is a complete tower base structure or a partial tower base structure of a polished structure on the surface of the silicon substrate, at least partially conforming to the shape of the side of the transmission layer away from the silicon substrate. For example, Figure 5 The contact area 71 in the tower contains a relatively complete tower base structure 12. For another example, Figure 6 , Figure 7 The contact area 71 in the tower contains part of the tower base structure 12.

[0052] It can be understood that the morphology of the tower base structure is related to the material of the silicon substrate and the texturing process. From a top view, its plane can be a polygon, for example, Figure 5 The square shown in the wireframe marked with 12 in the figure is not limited thereto, and may also be at least one of a rhombus, a square, a trapezoid, a nearly rhombus, a nearly square, and a nearly trapezoid. The morphology of a suitable tower base structure is conducive to forming a good bonding force with the electrode in the subsequent process. In the thickness direction, the tower base structure may protrude from the surface or be recessed from the surface, and this is not limited.

[0053] According to an embodiment of the present application, in order to facilitate the formation of at least one contact area 71 having a tower base structure 12, when using a laser to open the passivation anti-reflection layer, the position and size of the contact area can be controlled by controlling laser parameters, such as spot size, irradiation area, etc.; the tower base can adjust the polishing process, and the structure of the tower base, that is, the morphology and size of the ridges, can be controlled by controlling the process time, the type of additives, etc., and the size ratio and position relationship of the opening and the side length of the tower base can be adjusted to achieve this.

[0054] In one embodiment, referring to Figure 5 , the ratio of the maximum size d4 of an opening to the side length d5 ​​of a tower base structure is 0.5 to 5. The maximum size d4 of an opening refers to the maximum length of the opening. Specifically, if the ratio of d4 to d5 is less than 0.5, then d4 is too small, that is, the opening is too small. When an electrode is arranged above the opening, not only is the contact area between the electrode and the transmission layer exposed at the opening too small, which affects the transmission effect of current or carriers, but also the side length of the tower base structure is rougher. If the opening is too small, the opening covers too little tower base side length, and the roughness at the opening is too small, resulting in poor bonding or contact between the electrode and the transmission layer; when the ratio of d4 to d5 is greater than 5, the opening is too large, the opening covers too much tower base side length, and the tower base side length has a stronger light absorption capacity. When a laser is used for the opening process, the laser causes greater damage to the film layer below and around the opening, affecting the quality of the film layer, which is not conducive to carrier transmission. Therefore, in the present application, the ratio of the maximum size of the opening to the side length of the tower base structure is 0.5 to 5, which is at least the result of the damage to the film layer below and around the opening during the opening process, and the balance of the bonding strength and contact performance of the electrode and the transmission layer. The quality of the film layers such as the transmission layer, passivation anti-reflection layer below and around the opening is good, and good passivation effects can be achieved; at the same time, the bonding force between the electrode and the transmission layer is large, which prevents subsequent processes from pulling off, has strong reliability, and improves the bonding force or contact effect of the electrode and the transmission layer, while reducing the contact resistance and improving the current collection and conduction effects.

[0055] It should be noted that the side length of a tower foundation structure 12 refers to the length of the longest edge line among the edge lines 11 of the tower foundation structure 12 , or the average length of at least two edge lines 11 of the tower foundation structure 12 .

[0056] In the present application, the maximum size of the opening 6 may refer to: the maximum size of the side of the opening 6 away from the silicon substrate, or the maximum size of the side of the opening 6 close to the silicon substrate, or the maximum size of a position between the side of the opening 6 away from the silicon substrate and the side close to the silicon substrate, or the average of at least two of the above maximum sizes of an opening; or the average of the maximum sizes of multiple openings. For example, if the opening 6 is a circular opening, the maximum size of the opening is the diameter of the circle; if the opening is a square opening, the maximum size of the opening is the side length of the square.

[0057] Optionally, the maximum dimension d4 of the opening 6 is 10 μm to 45 μm, and the maximum dimension of the opening 6 is less than 10 μm. If the maximum dimension of the opening 6 is too small, the contact effect between the electrode 4 and the transmission layer will be poor. The maximum dimension of the opening 6 is greater than 45 μm. If the maximum dimension of the opening 6 is too large, the damage caused by the opening process will be too great. In the present application, the maximum dimension of the opening 6 is 10 μm to 45 μm, which is at least the result of an optimized balance between the contact effect between the electrode and the transmission layer and the damage caused by the opening process. The contact effect between the electrode and the transmission layer is good, and the damage caused by the opening process is small.

[0058] For example, the maximum dimension d4 of the opening 6 may be 10 μm, 10.5 μm, 11 μm, 12 μm, 13 μm, 15 μm, 18 μm, 20 μm, 22 μm, 25 μm, 28 μm, 30 μm, 35 μm, 40 μm, or 45 μm.

[0059] In one embodiment, the length of an edge 11 is 5um to 40um, and the length of the edge 11 is greater than 40um. The edge 11 is too long, and the position where the edge 11 is located is usually poor in flatness, so the light absorption capacity at the edge 11 is stronger. The edge 11 is too long to cause greater laser damage to the transmission layer at the edge 11. In addition, the position where the edge 11 is located is usually poor in flatness, and the quality of the film layer formed on the edge 11 is slightly poor. When the laser is used for the opening process, the edge 11 is too long, resulting in the laser damaging the film layer at the position of the edge 11. If the length of the ridge 11 is less than 5um, the ridge 11 is too short, and the ridge 11 is located at a position where the bonding force or contact effect between the electrode 4 and the transmission layer is poorly improved, affecting the current collection and conduction effects; therefore, in the present application, the length of an ridge 11 is 5um to 40um, which is at least the result of an optimized balance of multiple factors including the passivation quality, the processing damage of the opening, and the current collection and conduction effects. This not only ensures the passivation quality and avoids greater processing damage, but also ensures the current collection and conduction effects.

[0060] For example, the length of an edge line 11 can be 5um, 6um, 8um, 10um, 12um, 15um, 17um, 19um, 20um, 25um, 28um, 30um, 35um, or 40um.

[0061] In one embodiment, the side length d5 ​​of a tower base structure 12 is 5um to 40um, and the effect here is similar to the effect of a ridge line 11 having a length of 5um to 40um, and will not be described here to avoid repetition. For example, the side length d5 ​​of a tower base structure 12 can be 5um, 6.5um, 9um, 10um, 11um, 15um, 16um, 18um, 20um, 25um, 27um, 30um, 35um, 40um.

[0062] In some embodiments, in one example, referring to Figures 4 to 8 , at least one hole 9 is provided at the position of the ridgeline 11 in the contact area 71. Specifically, there is at least one hole 9 at the ridgeline, and the hole 9 and the surrounding parts are rougher, further increasing the surface roughness and specific surface area of ​​the opening area, so that the ridgeline of the surface has an uneven feature, so that the contact area between the electrode 4 and the transmission layer is larger, thereby further increasing the bonding force or contact effect between the electrode 4 and the transmission layer, improving the current collection and conduction effect, avoiding the risk of the electrode and the transmission layer falling off, and thus improving the performance and reliability of the solar cell.

[0063] Exemplarily, the maximum radial dimension of the hole 9 is greater than 0 μm and less than or equal to 3 μm. If the maximum radial dimension of the hole 9 is too large, for example, 3.5 μm, 4 μm or more, the number of holes 9 will be reduced, reducing the overall roughness of the contact area, thereby reducing the contact area between the transmission layer and the electrode, and reducing the bonding force between the electrode and the transmission layer. Therefore, the maximum radial dimension of the hole 9 in the present application is less than or equal to 3 μm.

[0064] It should be noted that, refer to Figures 4 to 7 , the rest of the contact area 71 of the transmission layer except the ridge 11 may also be distributed with holes, and the holes and the surrounding parts of the rest of the contact area 71 of the transmission layer except the ridge 11 are rougher, which also increases the surface roughness, thereby further increasing the bonding force or contact effect between the electrode 4 and the transmission layer, improving the current collection and conduction effect, and thus improving the performance of the solar cell. It should be noted that in the embodiment of the present application, the hole does not penetrate the transmission layer and is a blind hole.

[0065] In one embodiment, referring to Figure 8, the edge of the hole 9 has an annular protrusion 24, the annular shape here can be continuous distribution, i.e. a closed ring, or discontinuous distribution, i.e. a non-closed ring. The circular area surrounded by the bright circle in the figure is the hole 9, and the bright circle is the annular protrusion 24 formed on the edge of the hole. In some examples, the annular protrusion can make the material of the transmission layer melt first and then solidify during the process of the laser opening the passivation anti-reflection layer, and the above-mentioned protrusion 24 will be formed in the part around the hole 9, which is similar to a raised crater structure; for example, Figure 8 In the figure, for the two marked holes 9, a non-closed protrusion 24 is formed around the hole 9 on the left, and a closed protrusion 24 is formed around the hole 9 on the right. In the transmission layer: it is easier to form a three-dimensional structure at the position of the protrusion 24, and the uniformly distributed non-two-dimensional layer structure increases the surface roughness, thereby making the combination with the electrode 4 thereon more firmly, further increasing the bonding force or contact effect between the electrode 4 and the transmission layer, improving the current collection and conduction effect, and thus improving the performance and reliability of the solar cell.

[0066] It can be understood that the annular protrusion 24 is formed by melting and solidifying the transmission layer. When the transmission layer is doped polysilicon, the material of the annular protrusion 24 includes silicon.

[0067] In some embodiments, reference Figures 4 to 7 The density of holes at the ridges in the contact area 71 is greater than that of holes in other areas, and / or the density of protrusions at the ridges is greater than that of protrusions in other areas. There are more holes 9 and more protrusions at the ridges in the contact area 71. The holes 9, protrusions and their surrounding parts are rougher, which further increases the surface roughness and specific surface area of ​​the opening area, making the ridges on its surface have an uneven feature, so that the contact area between the electrode 4 and the transmission layer is larger, thereby further increasing the bonding force or contact effect between the electrode 4 and the transmission layer, improving the current collection and conduction effect, avoiding the risk of the electrode and the transmission layer falling off, and thus improving the performance and reliability of the solar cell.

[0068] The density of holes at the ridges in the contact area 71 refers to: the number of holes per unit distance on the ridges in the contact area 71, and the density of holes in other areas is similar to this; the density of protrusions at the ridges in the contact area 71 refers to: the number of protrusions per unit distance on the ridges in the contact area 71, and / or the protrusion distance of the protrusions per unit distance on the ridges in the contact area 71, and the density of protrusions in other areas is similar to this.

[0069] For example, Figure 4 and Figure 5In the contact area 71, at least some of the holes 9 at the position of the ridge 11 are interconnected, the density of the holes at the ridge is greater than the density of the holes in other areas, and the density of the protrusions at the ridge is greater than the density of the protrusions in other areas. Figure 6 and Figure 7 In the contact area 71, the holes 9 at the position of the ridge 11 are more interconnected, the protrusions at the ridge extend into strips along the ridge, and the density of the protrusions at the ridge is greater than the density of the protrusions in other areas. Figures 4 to 7 At least some of the holes 9 at the position of the ridgeline 11 in the contact area 71 are interconnected. After at least some of the holes at the ridgeline are interconnected, the density of the holes at the ridgeline in the contact area 71 is further increased, and the annular protrusions at the edges of adjacent holes are connected, which further increases the roughness at the ridgeline, increases the bonding force and contact effect between the electrode 4 and the opening area, and not only improves the current collection and conduction effect, but also improves the performance of the solar cell.

[0070] It should be noted that in the present application, at least some of the holes 9 at the position where the edge line 11 in the contact area 71 is located are interconnected, which specifically means that at least two holes 9 at the position where the edge line 11 in the contact area 71 are interconnected, and the degree of interconnection is not limited. Figures 4 to 5 The distribution density of the interconnected holes at the position of the ridge line 11 in the middle contact area 71 is relatively small. Figure 6 and Figure 7 The distribution density of interconnected holes at the position of the ridge line 11 in the middle contact area 71 is relatively high; in other words, Figures 4 to 5 The number of holes connected to each other at the position of the ridge line 11 in the middle contact area 71 is relatively small. Figure 6 and Figure 7 There are a large number of holes connected to each other at the locations where the ridges 11 are located in the middle contact area 71 . Figure 4 and Figure 5 In the contact area 71, the adjacent holes 9 at the position where the edge line 11 is located are adhered, Figure 6 and Figure 7 In the figure, the interconnectedness of the holes 9 at the position of the ridge line 11 in the contact area 71 is higher, forming a bright line. When laser is used for the opening process, the interconnectedness of the holes 9 at the position of the ridge line 11 in the contact area 71 is specifically related to the laser power during the laser opening process. When the laser power is higher, the interconnectedness of the holes 9 at the position of the ridge line 11 in the corresponding contact area 71 may be higher.

[0071] In some embodiments, reference Figure 6 to Figure 7The raised portion at the ridge 11 in the contact area 71 extends into a strip along the ridge, that is, the annular raised portions at the edges of adjacent holes are connected, further increasing the roughness at the ridge, increasing the bonding force and contact effect between the electrode 4 and the opening area, which not only improves the current collection and conduction effects, but also improves the performance of the solar cell.

[0072] In one embodiment, the height and width of the protrusion 24 are both less than or equal to 0.5 μm, the direction in which the height of the protrusion 24 is located is parallel to the direction Q in which the thickness of the silicon substrate 1 is located, and the width of the protrusion 24 is the maximum size of the protrusion 24 on a plane perpendicular to the direction in which the height of the protrusion 24 is located, which may be one plane or multiple planes, and the number of planes is determined by the levelness of each position of the protrusion 24. Specifically, when the height of the protrusion 24 is greater than 0.5um and / or the width of the protrusion 24 is greater than 0.5um, the roughness of the opening area is too large, so that the coverage uniformity of the transmission layer in the opening area becomes poor, which is not conducive to the collection and transmission of carriers here. The height and width of the protrusion 24 are both less than or equal to 0.5 μm, so that the roughness of the opening area is within a suitable range, which can not only meet the requirements of the electrode binding force, but also avoid the problem of uneven coverage of the transmission layer.

[0073] For example, the height and width of the protrusion 24 may be 0.5 μm, 0.48 μm, 0.45 μm, 0.42 μm, 0.4 μm, 0.39 μm, 0.38 μm, 0.35 μm, 0.32 μm, 0.3 μm, 0.28 μm, 0.25 μm, 0.22 μm, 0.2 μm, 0.18 μm, 0.15 μm, 0.12 μm, 0.1 μm, or 0.05 μm.

[0074] In some embodiments, reference Figures 4 to 7 , there is at least one hole 9 in the contact area, and the hole 9 here can be a hole located at the edge line 11, a hole outside the edge line 11 in the contact area, etc., and no specific limitation is made to this. The contact area 71 includes: a middle area and an edge area surrounding the middle area, and the middle area can include the geometric center of the contact area 71 or an area closer to the inside of the contact area 71; for a 71 contact area: the size of the hole 9 in the middle area is greater than the size of the hole 9 in the edge area. The size of the hole 9 here can refer to the area of ​​the hole 9, the maximum size of the hole 9, etc., and no specific limitation is made to this. The middle area of ​​the contact area 71 contributes more to the bonding force or contact effect of the contact between the electrode 4 and the transmission layer, the size of the hole 9 in the middle area of ​​the contact area 71 is larger, the bonding force or contact effect between the middle area of ​​the contact area 71 and the electrode 4 is better, and the bonding force or contact effect between the electrode 4 and the transmission layer is more enhanced, which further improves the current collection and conduction effect, thereby improving the performance of the solar cell.

[0075] It should be noted that, for a contact area 71, the relative size of the middle area and the edge area is not limited, and the areas of the two areas can be equal, or the middle area is larger than the edge area, or the edge area is larger than the middle area.

[0076] In some embodiments, reference Figures 4 to 7 , the area outside the contact area 71 on the side of the transmission layer away from the silicon substrate 1 is the non-contact area 72; the roughness of the contact area 71 is greater than the roughness of the non-contact area 72. Specifically, the side of the transmission layer exposed in the opening away from the silicon substrate is the contact area 71, and the side of the doping layer not exposed in the opening away from the silicon substrate is the non-contact area 72. The roughness of the contact area 71 can affect the bonding force or contact effect between the electrode 4 and the transmission layer. Specifically, the rougher the contact area 71, the more obvious the effect of improving the bonding force or contact effect between the electrode 4 and the transmission layer. The greater the surface roughness of the transmission layer exposed in the opening, the larger the contact area between the transmission layer and the electrode, which is more conducive to reducing the contact resistance and improving the carrier transmission capacity; and the transmission layer in the non-contact area 72 also has a passivation anti-reflection layer, which does not directly contact the electrode 4. Here, the quality requirements of the transmission layer and the film layer thereon are higher, so the non-contact area 72 is relatively flat, and the quality of the film layer formed thereon is better, which can achieve a better passivation effect, etc., thereby improving the performance of the solar cell.

[0077] It should be noted that the roughness of the contact area 71 and the roughness of the non-contact area 72 may both refer to surface roughness, which may be Ra roughness or Rz roughness. The roughness of the contact area 71 and the roughness of the non-contact area 72 are determined in the same way.

[0078] Exemplarily, the Ra roughness of the contact area 71 can be 0, 0.05μm, 0.08μm, 0.1μm, 0.12μm, 0.15μm, 0.18μm, 0.2μm, 0.25μm, 0.29μm, 0.3μm, 0.33μm, 0.35μm, 0.38μm, 0.4μm, 0.43μm, 0.45μm, 0.5μm, and the Ra roughness of the non-contact area 72 can be 0, 10nm, 15nm, 20nm, 25nm, 30nm, 35nm, 40nm, 45nm, 50nm, 55nm, 60nm, 65nm, 70nm, 75nm, 80nm, 85nm, 90nm, 95nm, 100nm.

[0079] In some embodiments, the shape of the opening 6 is at least one of a circle, a quasi-circle, a rectangle, and an ellipse, and the shape of the contact area 71 matches the shape of the opening 6 at the corresponding position. The opening 6 of the above shape is easy to achieve by laser opening. More importantly, in the process of the opening of the above shape by laser opening, the size and shape of the opening are easy to control, so that the shape and size of the opening are more accurate. It should be noted that the quasi-circle mentioned in this application means: approximately a circle. The shape of the opening 6 can also be a figure formed by splicing at least two of the shapes of circle, quasi-circle, rectangle, and ellipse, and there is no specific limitation on this.

[0080] For example, Figure 2 and Figure 3 In the example, the shape of the opening is circular. Figures 4 to 7 In the embodiment, the opening or contact area 71 is quasi-circular in shape.

[0081] In one embodiment, referring to Figure 2 and Figure 3 The transmission layer includes a plurality of transmission areas. On a transmission area, each contact area is arranged in a row at intervals to form a contact area row, or in other words, at a location where a transmission area is located, each opening 6 is arranged in a row at intervals to form an opening row. The arrangement of the above openings is easy to obtain by laser processing, and the accuracy is easy to control.

[0082] In one embodiment, referring to Figure 3 In a transmission zone, the number of contact area rows is greater than or equal to 2, and the contact areas in adjacent contact area rows are staggered, that is, the number of opening rows at the location of a transmission zone is greater than or equal to 2, and the openings 6 in adjacent opening rows are staggered. Through the staggered distribution, the distribution of contact areas in a transmission zone is more uniform, and then the transmission and collection distances of current at various positions in a transmission zone are roughly equal, which can achieve uniform collection and conduction of current, and the current collection and conduction effect is good.

[0083] For example, Figure 3 In one transmission area, the number of contact area rows is 2, and the contact areas in adjacent contact area rows are staggered. For another example, the number of contact area rows in one transmission area can also be 3, 4, 5, 6, etc., and the contact areas in adjacent contact area rows are staggered.

[0084] In some embodiments, reference Figure 2 and Figure 3On a transmission area, there is a gap between the contact area and the edge of the transmission area, that is, at the location of a transmission area, there is a gap between the opening 6 and the edge of the transmission area, that is, there is a reserved position between the opening 6 and the edge of the transmission area. On the one hand, it is conducive to alignment during the opening process, and the processing window of the opening is larger. On the other hand, it can avoid the thermal effect of the laser affecting the edge passivation during the opening process, and the edge still has a good passivation effect.

[0085] In one embodiment, referring to Figure 2 and Figure 3 , on a transmission area, there is a gap between the contact area and the edge of the transmission area, and in the extension direction M of the transmission area, the size d3 of the gap is 50μm to 200μm. Specifically, when d3 is less than 50μm, the opening 6 is too close to the edge of the transmission area, which is not conducive to alignment during the opening process, and the processing window of the opening is small, the yield is low, and the opening 6 is too close to the edge of the transmission area. The thermal effect of the laser during the opening process will affect the edge passivation and weaken the edge passivation effect; when d3 is greater than 200μm, the opening 6 is too far from the edge of the transmission area, and the current or carrier transmission distance at the edge of the transmission area is too far, the transmission damage is large, and it is not conducive to the collection and conduction of current. Therefore, in the present application, d3 is 50μm to 200μm, which at least achieves a balance among multiple factors including the difficulty of alignment during the opening process, the processing window of the opening, the opening yield, edge passivation, and current collection at the edge of the transmission zone. It not only reduces the difficulty of alignment during the opening process and facilitates alignment, but also has a larger processing window for the opening and a higher yield. In addition, the thermal influence of the laser during the opening process basically does not affect the edge passivation, thereby maintaining a good passivation effect on the edge and ensuring the current collection effect at the edge of the transmission zone.

[0086] For example, in a transmission zone, there is a gap between the contact area and the edge of the transmission zone. In the extension direction M of the transmission zone, the size d3 of the gap can be: 50μm, 60μm, 80μm, 90μm, 100μm, 120μm, 150μm, 180μm, 190μm, 200μm.

[0087] In one embodiment, referring to Figure 2 and Figure 3, the transmission layer includes: a first transmission layer and a second transmission layer, the first transmission layer and the second transmission layer have different doping types, that is, the first transmission layer is one of the P-type transmission layer and the N-type transmission layer, and the second transmission layer is the other of the P-type transmission layer and the N-type transmission layer. For example, the first transmission layer is a P-type transmission layer, and the second transmission layer is an N-type transmission layer. For another example, the second transmission layer is a P-type transmission layer, and the first transmission layer is an N-type transmission layer. The side length of the tower base structure 12 in the first transmission layer is less than the side length of the tower base structure 12 in the second transmission layer; and / or, the depth of the tower base structure 12 in the first transmission layer is greater than the depth of the tower base structure 12 in the second transmission layer. Specifically, the relative size relationship of the above-mentioned dimensions is related to the number of etchings received by the corresponding transmission layer, the specific material, size, opening damage of the transmission layer, etc. In the case of the relative size relationship of the above-mentioned dimensions, the damage to each film layer during the opening process is relatively small, ensuring that different regions have good transmission performance and improving the conversion efficiency of solar cells.

[0088] For example, the solar cell is a TBC solar cell, referring to Figure 1 The TBC solar cell is a back contact solar cell, wherein the first transmission layer is a P-type transmission layer, specifically a P-type doped polysilicon layer, and the second transmission layer is an N-type transmission layer, specifically an N-type doped polysilicon layer. A tunneling oxide layer 3 is also provided between the first transmission layer and the second transmission layer and the silicon substrate 1. In the process of preparing the TBC solar cell, the P-type doped polysilicon layer can be prepared first, and then the N-type doped polysilicon layer can be prepared. In the TBC solar cell: the side length of the tower base structure 12 in the P-type doped polysilicon layer is less than the side length of the tower base structure 12 in the N-type doped polysilicon layer; and / or, the depth of the tower base structure 12 in the P-type doped polysilicon layer is greater than the depth of the tower base structure 12 in the N-type doped polysilicon layer.

[0089] It should be noted that in the present application, the depth of the tower foundation structure refers to: when the tower foundation structure protrudes from other parts in the contact area, the depth of the tower foundation structure refers to the size of the other parts of the tower foundation structure protruding from the contact area, which may be the size of the other parts protruding from the contact area at one position in the tower foundation structure, or may be the average value of the sizes of the other parts protruding from the contact area at multiple positions in the tower foundation structure; when the tower foundation structure is recessed in other parts of the contact area, the depth of the tower foundation structure refers to the size of the other parts of the tower foundation structure recessed in the contact area, which may be the size of the other parts of the tower foundation structure recessed in the contact area at one position in the tower foundation structure, or may be the average value of the sizes of the other parts of the tower foundation structure recessed in the contact area at multiple positions in the tower foundation structure. The depth of the tower foundation structure in different transmission layers is determined in the same way.

[0090] In some embodiments, reference Figure 2 and Figure 3, the transmission layer includes several transmission areas, that is, the first transmission layer includes several transmission areas, and the second transmission layer includes several transmission areas, Figure 2 and Figure 3 In the figure, 73 can be a transmission area in the first transmission layer, and 74 can be a transmission area in the second transmission layer. The transmission area of ​​the first transmission layer and the transmission area of ​​the second transmission layer are alternately distributed along the direction L. At the location of a transmission area, each opening 6 is spaced and arranged in a row to form an opening row. In an opening row, the spacing between adjacent openings is d1, and d1 is 20um to 100um. Specifically, in an opening row, the spacing between adjacent openings d1 < 20um, d1 is too small, the number of openings formed in a transmission area is too large, and the damage caused by the process during the opening is more, d1 > 100um, d1 is too large, the number of openings formed in a transmission area is too small, the transmission distance of the current or carrier is too long, the transmission loss is large, and the current collection and conduction effect is poor. Therefore, d1 is 20um to 100um, which is the result of a balance between the damage caused by the opening and the current collection and conduction effect, and the damage caused by the opening is less and the current collection and conduction effect is good. The direction of d1 here is parallel to the extension direction of the transmission area. d1 may be the distance between the geometric centers of a pair of adjacent openings in an opening row, or d1 may be the average value of the distances between the geometric centers of multiple adjacent pairs of openings in an opening row.

[0091] For example, d1 here can be 20um, 30um, 40um, 50um, 55um, 60um, 70um, 80um, 90um, or 100um.

[0092] In some embodiments, reference Figure 3 , at the location of a transmission zone, the number of opening rows is greater than or equal to 2, and the distance d2 between adjacent opening rows is 20um to 50um. Specifically, the spacing d2 between adjacent opening rows is less than 20um. If d2 is too small, there are too many opening rows formed in a transmission zone, and the damage caused by the openings is more. If d2 is greater than 50um, there are too few opening rows formed in a transmission zone, and the transmission distance of the current or carrier is too long, the transmission loss is large, and the current collection and conduction effect is poor. Therefore, d2 of 20um to 50um is the result of a balance between the damage caused by the openings and the current collection and conduction effect. The damage caused by the openings is less and the current collection and conduction effect is good. The direction L where d2 is located is perpendicular to the extension direction M of the transmission zone. d2 can be the distance between the geometric centers of two openings 6 in adjacent opening rows in the direction L perpendicular to the extension direction M of the transmission zone.

[0093] For example, d2 here can be 20um, 23um, 25um, 30um, 35um, 37um, 40um, 45um, 47um, or 50um.

[0094] In one embodiment, referring to Figure 2 and Figure 3 In the case where the first transmission layer and the second transmission layer are both located on the same surface of the silicon substrate, that is, both are located on the backlight surface of the silicon substrate, an isolation region 8 is further provided between the transmission region 73 of the adjacent first transmission layer and the transmission region 74 of the adjacent second transmission layer to avoid short circuit. The isolation region 8 may be a suede structure or a polished structure, which is not limited thereto. For example, the isolation region 8 may be a suede structure to increase the light trapping effect.

[0095] In some embodiments, the depth of the tower base structure 12 in the first transmission layer is 0.4um to 2um, and the depth of the tower base structure 12 in the second transmission layer is 0.4um to 1.5um. Specifically, the depth of the tower base structure 12 is related to the film-forming quality of the film layer on it, as well as the bonding force or contact effect between the electrode 4 and the transmission layer. If the depth of the tower base structure 12 is too large, the film-forming quality of the film layer on it is poor, and the passivation effect is poor. If the depth of the tower base structure 12 is too small, the gain effect of the bonding force or contact effect between the electrode 4 and the transmission layer is poor. For the first transmission layer and the second transmission layer, the tower base structure 12 is respectively within the above range, which is an optimized balance of multiple factors such as the film-forming quality, passivation effect, and current collection and conduction effect of the film layer on it, which can improve the performance of solar cells.

[0096] For example, for the above-mentioned TBC solar cell, the depth of the tower base structure in the P-type doped polysilicon layer can be 0.4um to 2um, and the depth of the tower base structure in the N-type doped polysilicon layer can be 0.4um to 1.5um. For another example, the depth of the tower base structure 12 in the first transmission layer and the P-type doped polysilicon layer can be 0.4um, 0.5um, 0.8um, 0.9um, 1um, 1.2um, 1.4um, 1.5um, 1.6um, 1.8um, 1.9um, 2um, and the depth of the tower base structure 12 in the second transmission layer and the N-type doped polysilicon layer can be 0.4um, 0.5um, 0.6um, 0.8um, 0.92um, 1um, 1.1um, 1.2um, 1.4um, 1.5um. It should be noted that, for the same solar cell, in the process of determining the depth of the tower base structure in the first transmission layer and the depth of the tower base structure in the second transmission layer, it is necessary to ensure that the depth of the tower base structure in the first transmission layer is greater than the depth of the tower base structure in the second transmission layer.

[0097] In one embodiment, the side length of the tower base structure 12 in the first transmission layer is 5um to 20um, and the side length of the tower base structure 12 in the second transmission layer is 10um to 40um. Specifically, the side length of the tower base structure 12 is related to the film-forming quality of the film layer thereon, and the bonding force or contact effect between the electrode 4 and the transmission layer. If the side length of the tower base structure 12 is too long, the film-forming quality of the film layer thereon is poor, and the passivation effect is poor. If the side length of the tower base structure 12 is too short, the gain effect on the bonding force or contact effect between the electrode 4 and the transmission layer is poor. For the first transmission layer and the second transmission layer, the tower base structure 12 is within the above range respectively, which is an optimized balance of multiple factors such as the film-forming quality of the film layer thereon, the passivation effect, and the current collection and conduction effect, which can improve the performance of solar cells.

[0098] For example, for the above-mentioned TBC solar cell, the side length of the tower base structure in the P-type doped polysilicon layer can be 5um to 20um, and the side length of the tower base structure in the N-type doped polysilicon layer can be 10um to 40um. For another example, the side length of the tower base structure 12 in the first transmission layer and the P-type doped polysilicon layer can be 5um, 6um, 8um, 9um, 10um, 12um, 14um, 15um, 16um, 18um, 19um, 20um, and the side length of the tower base structure 12 in the second transmission layer and the N-type doped polysilicon layer can be 10um, 12.5um, 14um, 15um, 17um, 20um, 22um, 25um, 27um, 30um, 35um, 40um. It should be noted that in the same solar cell, in the process of determining the side length of the tower base structure in the first transmission layer and the side length of the tower base structure in the second transmission layer, it is necessary to ensure that the side length of the tower base structure in the first transmission layer is less than the side length of the tower base structure in the second transmission layer.

[0099] In some embodiments, reference Figure 1 and Fig. 9The transmission layer includes a polycrystalline silicon doped layer 2, a polycrystalline silicon region containing polycrystalline silicon in the polycrystalline silicon doped layer 2, and an amorphous silicon region 21 in the polycrystalline silicon doped layer 2. The amorphous silicon region 21 contains amorphous silicon, and the amorphous silicon region 21 is located at a portion of the polycrystalline silicon doped layer 2 away from the silicon substrate 1. The amorphous silicon region 21 is located below the opening 6. At the same time, the amorphous silicon region 21 is also located between the passivation anti-reflection layer 5 and the polycrystalline silicon region, and is located at the position of the opening 6. It should be noted that in the thickness direction Q of the silicon substrate 1, the polycrystalline silicon region is closer to the silicon substrate than the amorphous silicon region 21. The electrode 4 is located in the contact area and contacts the amorphous silicon region 21 to realize current collection and conduction. Compared with the polysilicon doped layer 2, the amorphous silicon in the amorphous silicon region 21 is more resistant to acid corrosion. Therefore, the amorphous silicon region 21 located below the opening 6 and between the passivation anti-reflection layer 5 and the polysilicon region and adjacent to the opening 6 can protect the film layer below the amorphous silicon region 21, for example, it can protect the polysilicon doped layer 2, so that the film layer below it has better weather resistance during long-term service, thereby maintaining the reliability and stability of the solar cell during long-term service; and the passivation anti-reflection layer 5 is located between the polysilicon region and adjacent to the opening 6. It is a non-contact area. Compared with the polysilicon doped layer 2, the conductivity of amorphous silicon is slightly weaker. It is located between the passivation anti-reflection layer 5 and the polysilicon area, and the amorphous silicon area 21 near the opening 6 can block the carriers in the non-contact area, thereby reducing the recombination between the polysilicon doped layer 2 and the metal in the electrode 4; in addition, compared with the polysilicon doped layer 2 and the passivation anti-reflection layer 5, the refractive index of amorphous silicon is larger, which can increase the path of light in the solar cell, reduce reflected light, better increase the light trapping effect, and improve the battery performance. For example, the silicon nitride layer is the farthest from the silicon substrate in the passivation anti-reflection layer 5. The refractive index of amorphous silicon is about 4.0, which is greater than the refractive index of the silicon nitride layer and the polysilicon doped layer 2. Therefore, it can increase the path of light in the solar cell, reduce reflected light, better increase the light trapping effect, and improve the battery performance.

[0100] In some embodiments, the thickness of amorphous silicon at the ridge is greater than the thickness of amorphous silicon in other areas, which can fully protect the film layer under the amorphous silicon region 21 at the ridge, for example, can protect the polysilicon doping layer 2, so that the film layer thereunder has better weather resistance during long-term service, thereby maintaining the reliability and stability of the solar cell during long-term service.

[0101] In one embodiment, Figure 1, the direction shown by M is the direction of the width of the opening 6, which can also be understood as a direction parallel to the silicon substrate or a direction perpendicular to the thickness of the silicon substrate. On one side of an opening 6, the extension length of the amorphous silicon region 21 along the width of the opening in the direction away from the opening is less than or equal to 6μm, and the extension length here is greater than 0. If the extension length is too large, it may be detrimental to the transmission and collection of carriers. The opening 6 is usually formed by laser, and the laser damage caused by the extension length being too large may also be large. For example, the extension length of the amorphous silicon region 21 located on the side of the passivation anti-reflection layer 5 close to the silicon substrate along the width of the opening 6 in the direction away from the opening is approximately 2.42μm. For another example, the extension length can be 6μm, 5.5μm, 5.3μm, 5μm, 4.5μm, 4μm, 3.5μm, 3μm, 2.5μm, 2μm, 1.5μm, 1μm, 0.5μm, 0.2μm.

[0102] It should be noted that, in the present application, the direction away from the opening along the width of the opening refers to a direction parallel to the direction M where the width of the opening is located and away from the geometric center of the opening.

[0103] In one embodiment, in the direction Q where the thickness of the silicon substrate 1 is located, the thickness of the amorphous silicon region 21 is 1nm to 70nm. In a solar cell, if the thickness of the amorphous silicon region 21 is greater than 70nm, the carrier transport capability will be affected. If the thickness of the amorphous silicon region 21 is less than 1nm, the barrier effect on recombination is poor. If the thickness of the amorphous silicon region 21 is 1nm to 70nm, at least an optimal balance between the carrier transport capability and the barrier effect on recombination is achieved, which not only plays a good role in carrier transport, but also has a good barrier effect on recombination. For example, the average thickness of the amorphous silicon region 21 is about 15nm, and an amorphous silicon region with a thickness of 52.84nm may appear, which is mainly caused by the uneven energy of the laser. The location with greater laser energy has higher heat, which will form a thicker amorphous silicon layer.

[0104] For example, the thickness at different positions in the amorphous silicon region 21 may be 8.38 nm, 13.04 nm, 12.18 nm, or the thickness at different positions in the amorphous silicon region 21 may be 8.65 nm, 12.01 nm. For another example, the thickness of the amorphous silicon region 21 may be 1 nm, 10 nm, 12.55 nm, 9.19 nm, 14.07 nm, 14.58 nm, 16.36 nm, 18.99 nm, 20 nm, 25 nm, 30 nm, 31.05 nm, 35 nm, 40 nm, 45 nm, 50 nm, 55 nm, 60 nm, 65 nm, 70 nm.

[0105] For another example, at the edge of the opening 6, the thickness of the amorphous silicon region 21 may be 14nm, 14.8nm, 14.5nm, 15nm, 15.5nm, 16nm, 16.5nm, or 17nm. For another example, below the opening 6, the thickness of the amorphous silicon region 21 may be 8nm, 9nm, 8.5nm, 9.5nm, 10nm, 10.5nm, 10.8nm, 11nm, 11.5nm, 11.8nm, 12nm, 12.5nm, 13nm, or 16nm.

[0106] In one embodiment, referring to Fig. 9 The polycrystalline silicon doped layer also has: micron crystals and / or nano crystals 22. In the direction Q where the thickness of the silicon substrate 1 is located, the micron crystals and / or nano crystals 22 are closer to the silicon substrate 1 than the amorphous silicon region 21. The conductivity of nanocrystalline silicon and / or microcrystalline silicon is higher than that of amorphous silicon, which can improve the transmission efficiency of carriers.

[0107] In one embodiment, the orthographic projection of the micron-crystal and / or nano-crystal 22 on the first surface at least partially overlaps with the orthographic projection of the opening on the first surface, which may mean: the orthographic projection of the micron-crystal and / or nano-crystal 22 on the first surface completely overlaps with the orthographic projection of the opening on the first surface, and the areas of the two orthographic projections are equal; or, the orthographic projection of the micron-crystal and / or nano-crystal 22 on the first surface covers the orthographic projection of the opening on the first surface and is larger than the orthographic projection of the opening on the first surface; or, the orthographic projection of the opening on the first surface covers the micron-crystal and / or nano-crystal 22. The orthographic projection of the opening on the first surface is greater than the orthographic projection of the micron-crystal and / or nano-crystal 22 on the first surface, or the orthographic projection of the micron-crystal and / or nano-crystal 22 on the first surface covers part of the orthographic projection of the opening on the first surface and is greater than the orthographic projection of the opening on the first surface; or the orthographic projection of the opening on the first surface covers part of the orthographic projection of the micron-crystal and / or nano-crystal 22 on the first surface and is greater than the orthographic projection of the micron-crystal and / or nano-crystal 22 on the first surface. Nanocrystalline silicon and / or microcrystalline silicon has higher electrical conductivity than amorphous silicon, which can improve the carrier transmission efficiency.

[0108] The orthographic projection of the microcrystal and / or nanocrystal 22 on the first surface refers to the projection of the microcrystal and / or nanocrystal 22 on the first surface when the microcrystal and / or nanocrystal 22 is irradiated with light perpendicular to the first surface. The orthographic projection of the opening on the first surface is similar.

[0109] In one embodiment, referring to Fig. 9The polysilicon doping layer 2 includes: a polysilicon region 23, and the polysilicon region 23 contains polysilicon. The lattice size in the micron crystal and / or nano crystal 22 and the polysilicon region 23 is 0.01nm to 1nm. Specifically, the change of the lattice size in the micron crystal and / or nano crystal 22 and the polysilicon region 23 will cause the change of the band structure, thereby affecting the behavior of the carriers, and also affecting their movement and recombination process. The lattice size in the micron crystal and / or nano crystal 22 and the polysilicon region 23 is within the above range, which can increase the life of the carriers, and at the same time, the absorption peak is higher, which is conducive to improving the photoelectric conversion efficiency and reducing the recombination. That is to say, the lattice size in the micron crystal and / or nano crystal 22 and the polysilicon region 23 is within the above range, which is the result of a balance of at least three factors: the life of the carriers, the photoelectric conversion efficiency, and the recombination.

[0110] For example, the lattice size in the microcrystals and / or nanocrystals 22 and the polysilicon regions 23 may be 0.01 nm, 0.02 nm, 0.05 nm, 0.1 nm, 0.15 nm, 0.2 nm, 0.25 nm, 0.3 nm, 0.35 nm, 0.4 nm, 0.45 nm, 0.5 nm, 0.55 nm, 0.6 nm, 0.65 nm, 0.7 nm, 0.75 nm, 0.8 nm, 0.85 nm, 0.9 nm, 0.95 nm, or 1 nm.

[0111] It should be noted that the lattice size may be the same or may increase from the micron crystal and / or nano crystal 22 to the polysilicon region 23. The lattice size of the micron crystal and / or nano crystal 22 and the polysilicon region 23 may preferably be 0.31 nm. The lattice size in the micron crystal and / or nano crystal 22 may refer to the size of a lattice in the micron crystal and / or nano crystal, or the average value of multiple lattice sizes, and the lattice size of the polysilicon region 23 is similar.

[0112] The present application also provides a method for preparing a solar cell, comprising the following steps.

[0113] Step 101, providing a silicon substrate; in a thickness direction of the silicon substrate, the silicon substrate has a first surface and a second surface opposite to each other.

[0114] Step 102: sequentially prepare a transmission layer and a passivation anti-reflection layer on at least one of the first surface and the second surface.

[0115] The transmission layer can be formed by LPCVD (low pressure chemical vapor deposition) and other methods, and the specific formation method of the transmission layer is not limited. The preparation method of the passivation anti-reflection layer is not specifically limited, for example, deposition and other methods can be used.

[0116] Step 103, using laser opening to form a plurality of openings in the passivation anti-reflection layer; the area corresponding to the openings on the side of the transmission layer away from the silicon substrate is a contact area; at least one of the contact areas has an edge line.

[0117] There is no limitation on the specific parameters of the laser. For example, a picosecond laser engraving process can be used to engrave and open the passivation anti-reflection layer according to the designed collector grid line pattern to form the required micron-level groove structure.

[0118] Step 104: forming an electrode in the contact area, wherein the electrode contacts the transmission layer.

[0119] There is no specific limitation on the specific preparation method of the electrode. For example, a seed layer 41 may be prepared first, and then a slurry may be screen-printed on the side of the seed layer away from the silicon substrate and dried to form a slurry layer 42. The slurry layer may be formed by low-temperature silver-coated copper slurry, low-temperature copper slurry, low-temperature nickel slurry, etc. The slurry layer uses low-temperature silver-free metallization technology, which not only avoids the price and supply disadvantages of silver paste products, but also saves resource consumption caused by high-temperature technology. At the same time, it can avoid the heat effect brought by high-temperature technology, which can effectively reduce production costs.

[0120] In one embodiment, in the aforementioned step 103, a first laser power is used to perform laser opening to form a plurality of first openings; a second laser power is used to perform laser opening to form a plurality of second openings; at least one hole 9 is provided at the position of the ridgeline 11 in the contact region 71; at least some of the holes 9 at the position of the ridgeline in the contact region 71 are interconnected. The first laser power here is greater than the second laser power; the number of holes interconnected at the position of the ridgeline in the contact region corresponding to the first opening is greater than the number of holes interconnected at the position of the ridgeline in the contact region corresponding to the second opening; and / or, the distribution density of holes interconnected at the position of the ridgeline in the contact region corresponding to the first opening is greater than the distribution density of holes interconnected at the position of the ridgeline in the contact region corresponding to the second opening. That is, the greater the laser power, the greater the degree of connectivity of the holes interconnected at the position of the ridgeline in the contact region. It should be noted that in the comparison process here, the number of holes interconnected or the distribution density of holes interconnected is determined within the same area or unit area at the position of the ridgeline in the contact region.

[0121] It should be noted that the solar cell and the preparation method thereof provided in the present application are applicable to whether the transmission layer is an N-type transmission layer or a P-type transmission layer.

[0122] The present application also provides a photovoltaic module, including any of the aforementioned solar cells. The photovoltaic module may also include a packaging film located on both sides of the solar cell, and other structures in the photovoltaic module are not specifically limited.

[0123] The photovoltaic assembly may also include an electrical connector, where the electrical connector may serve as a conductive interconnection, for example, the electrical connector may be a welding strip or a conductive backplane, etc., and there is no specific limitation on the electrical connector. The electrical connector is electrically connected to the aforementioned electrodes in at least two of the aforementioned solar cells, where the electrical connector may be directly electrically connected to the aforementioned electrodes, or indirectly electrically connected, and there is no limitation on this. The electrical connector may electrically connect the positive polarity electrode in one of the two adjacent aforementioned solar cells to the negative polarity electrode in the other solar cell, to achieve conductive interconnection.

[0124] It should be noted that in the present application, the relevant parts among the photovoltaic module, the solar cell and the method for preparing the solar cell can be referenced to each other, and can achieve the same or similar beneficial effects. In order to avoid repetition, they will not be described here.

[0125] It should be noted that, in this article, the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the sentence "comprises a ..." does not exclude the existence of other identical elements in the process, method, article or device including the element.

[0126] The embodiments of the present invention are described above in conjunction with the accompanying drawings, but the present invention is not limited to the above-mentioned specific implementation modes, which are merely illustrative rather than restrictive. Under the guidance of the present invention, ordinary technicians in this field can also make many forms without departing from the scope of protection of the present invention and the claims, all of which are within the protection of the present invention.

Claims

1. A solar cell, characterized in that: include: Silicon substrate; In the direction of the thickness of the silicon substrate, the silicon substrate has a first surface and a second surface opposite to each other; A transmission layer and a passivation anti-reflection layer are stacked on at least one of the first surface and the second surface; in the direction where the thickness of the silicon substrate is located, the transmission layer is located between the silicon substrate and the passivation anti-reflection layer; the passivation anti-reflection layer has a plurality of openings; the area corresponding to the opening on the side of the transmission layer away from the silicon substrate is a contact area; at least one of the contact areas has a ridge line; An electrode is arranged on a side of the passivation anti-reflection layer away from the silicon substrate, and the electrode passes through the opening to contact the transmission layer.

2. The solar cell according to claim 1, characterized in that: At least one of the contact areas has a tower base structure, and the ridge line includes: the side length of the tower base structure.

3. The solar cell according to claim 1, characterized in that There is at least one hole in the contact area at the location of the ridge line.

4. The solar cell according to claim 3, characterized in that: The edge of the hole has an annular protrusion.

5. The solar cell according to claim 4, characterized in that The density of holes at the ridges is greater than the density of holes in other regions, and / or the density of protrusions at the ridges is greater than the density of protrusions in other regions.

6. The solar cell according to claim 4, characterized in that: At least some of the holes at the position where the ridge line is located are interconnected, and / or the protrusion at the ridge line extends into a strip along the ridge line.

7. The solar cell according to claim 1, characterized in that The contact area has a plurality of holes; the contact area includes: a middle area and an edge area surrounding the middle area; for one of the contact areas: the size of the holes in the middle area is greater than the size of the holes in the edge area.

8. The solar cell according to claim 1, characterized in that The area outside the contact area on the side of the transmission layer facing away from the silicon substrate is a non-contact area; The roughness of the contact area is greater than the roughness of the non-contact area.

9. The solar cell according to claim 1, characterized in that: The transmission layer comprises a plurality of transmission areas, and on one of the transmission areas, the contact area has a spacing from an edge of the transmission area.

10. The solar cell according to claim 9, characterized in that: In the extending direction of the transmission area, the size of the interval is 50 μm to 200 μm.

11. The solar cell according to claim 2, characterized in that: The ratio of the maximum dimension of one of the openings to the side length of one of the tower base structures is 0.5 to 5.

12. The solar cell according to claim 2, characterized in that: The transmission layer comprises: a first transmission layer and a second transmission layer, wherein the first transmission layer and the second transmission layer have different doping types; The side length of the tower base structure in the first transmission layer is smaller than the side length of the tower base structure in the second transmission layer; and / or, The depth of the tower base structure in the first transmission layer is greater than the depth of the tower base structure in the second transmission layer.

13. The solar cell according to claim 2, characterized in that: The length of one of the ridge lines is 5um to 40um, and / or the side length of one of the tower base structures is 5um to 40um.

14. The solar cell according to claim 4, characterized in that: The height and width of the protrusion are both less than or equal to 0.5 μm; the direction of the height is parallel to the direction of the thickness of the silicon substrate, and the width is the maximum dimension of the protrusion on a plane perpendicular to the direction of the height.

15. The solar cell according to any one of claims 1 to 14, characterized in that The transmission layer includes a polysilicon doped layer; the polysilicon doped layer has a polysilicon region and an amorphous silicon region, and the amorphous silicon region is located on a side of the polysilicon doped layer away from the silicon substrate; the amorphous silicon region is located between the passivation anti-reflection layer and the polysilicon region, and is located at the position of the opening.

16. The solar cell according to claim 15, characterized in that: The thickness of the amorphous silicon at the ridge line is greater than the thickness of the amorphous silicon in other areas.

17. The solar cell according to any one of claims 1 to 14, characterized in that The electrode includes a stacked seed layer and a non-fire-through type slurry layer.

18. A photovoltaic module, characterized in that: include: A solar cell as claimed in any one of claims 1 to 17.

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