Back contact battery and preparation method thereof

Abstract

The invention relates to the photovoltaic field, and provides a back contact cell and a preparation method thereof, and the preparation method of the back contact cell comprises the steps: providing a substrate which comprises a first surface and a second surface which are opposite to each other; the first surface is provided with first regions and second regions which are alternately arranged, and spacer regions located between the first regions and the second regions, the first regions are provided with first emitters, the second regions are provided with second emitters, and doped elements in the first emitters and doped elements in the second emitters have different conduction types; the thickness of the first emitter is smaller than that of the second emitter; printing a first grid line on the first area of the second surface by adopting a first screen printing plate, wherein the first grid line is in electric contact with the first emitting electrode; and printing a second grid line on the second area of the second surface by adopting a second screen printing plate, wherein the second grid line is electrically contacted with the second emitting electrode. The reliability of preparing the back contact battery can be improved at least.

Description

Technical Field

[0001] The present disclosure relates to the photovoltaic field, and in particular to a back contact cell and a preparation method thereof. Background Art

[0002] As fossil energy is gradually depleted, solar energy is becoming more and more widely used as a new energy alternative. Solar cells are devices that convert sunlight into electrical energy. Solar cells use the photovoltaic principle to generate carriers, and then use electrodes to lead the carriers out, which is conducive to the effective use of solar energy.

[0003] The current solar cells mainly include back contact cells, TOPCON (Tunnel Oxide Passivated Contact) cells, PERC (Passivated Emitter and Real Cell) and heterojunction cells, etc. Among them, the positive and negative grid lines of the back contact cell are set on the back, and there is no grid line blocking on the front. Compared with conventional solar cells, it can reduce the light energy loss caused by grid line blocking and has higher photoelectric conversion efficiency.

[0004] However, the back contact battery in the related art has problems when printing the grid lines, resulting in poor reliability in preparing the back contact battery. Summary of the invention

[0005] The embodiments of the present disclosure provide a back-contact battery and a method for preparing the same, which can at least improve the reliability of preparing the back-contact battery.

[0006] According to some embodiments of the present disclosure, on the one hand, an embodiment of the present disclosure provides a method for preparing a back-contact battery, and the method for preparing a back-contact battery includes: providing a substrate, the substrate including a first surface and a second surface opposite to each other; the second surface is provided with first areas and second areas arranged alternately, and a spacing area located between the first areas and the second areas, a first emitter is provided on the first area, and a second emitter is provided on the second area, the doping element in the first emitter and the doping element in the second emitter have different conductivity types, and the thickness of the first emitter is less than the thickness of the second emitter; using a first screen to print a first gate line on the first area of ​​the second surface, the first gate line is electrically contacted with the first emitter; using a second screen to print a second gate line on the second area of ​​the second surface, the second gate line is electrically contacted with the second emitter.

[0007] In some embodiments, before printing the first gate line, the method for preparing the back-contact battery also includes: forming a first passivation layer, the first passivation layer is located on the surface of the first emitter and the second emitter facing away from the substrate, and is also located on the spacing area of ​​the second surface; the height of the surface of the first gate line facing away from the substrate relative to the second surface is a first height, the height of the surface of the first passivation layer on the second area facing away from the substrate relative to the second surface is a second height, the first height is greater than the second height, and the difference between the first height and the second height is less than or equal to 4μm.

[0008] In some embodiments, before printing the first gate line, the method for preparing the back-contact battery also includes: forming a first passivation layer, the first passivation layer is located on the surface of the first emitter and the second emitter facing away from the substrate, and is also located on the spacing area of ​​the second surface; the height of the surface of the first gate line facing away from the substrate relative to the second surface is a first height, the height of the surface of the first passivation layer on the second area facing away from the substrate relative to the second surface is a second height, and the first height is equal to the second height.

[0009] In some embodiments, a difference between a thickness of the first emitter and a thickness of the second emitter is less than or equal to 100 nm.

[0010] In some embodiments, the thickness of the first emitter is 60 nm to 380 nm, and the thickness of the second emitter is 60 nm to 400 nm.

[0011] In some embodiments, the thickness of the first gate line is less than the thickness of the second gate line.

[0012] In some embodiments, the thickness of the first gate line is 2 μm-20 μm, and the thickness of the second gate line is 5 μm-30 μm.

[0013] In some embodiments, the ratio of the projection area of ​​the first emitter on the second surface to the area of ​​the second surface is 0.1-0.4, and the ratio of the projection area of ​​the second emitter on the second surface to the area of ​​the second surface is 0.1-0.4.

[0014] In some embodiments, along the first direction, the width of the first emitter is 150 μm-300 μm, and the width of the second emitter is 150 μm-300 μm.

[0015] According to some embodiments of the present disclosure, on the other hand, the embodiments of the present disclosure further provide a back-contact battery, which includes: a substrate, the substrate including a first surface and a second surface opposite to each other; the second surface is provided with first and second regions alternately arranged, and a spacing region located between the first regions and the second regions, a first emitter is provided on the first region, a second emitter is provided on the second region, the doping elements in the first emitter and the doping elements in the second emitter have different conductivity types, and the thickness of the first emitter is less than the thickness of the second emitter; a first gate line, the first gate line is located on the first region and is electrically contacted with the first emitter; a second gate line, the second gate line is located on the second region and is electrically contacted with the second emitter.

[0016] The technical solution provided by the embodiments of the present disclosure has at least the following advantages: The technical solution of the preparation method of the back-contact battery provided in the embodiment of the present disclosure includes: providing a substrate, the substrate including a first surface and a second surface opposite to each other; the second surface is provided with a first area and a second area arranged alternately, and a spacing area located between the first area and the second area, a first emitter is provided on the first area, and a second emitter is provided on the second area, the doping element in the first emitter and the doping element in the second emitter have different conductivity types, and the thickness of the first emitter is less than the thickness of the second emitter; using a first screen to print a first gate line on the first area of ​​the second surface, the first gate line is electrically in contact with the first emitter; using a second screen to print a second gate line on the second area of ​​the second surface, the second gate line is electrically in contact with the second emitter.

[0017] In the embodiment of the present disclosure, the first grid line is first printed on the first area provided with the first emitter of smaller thickness by using the first screen, and then the second grid line is printed on the second area provided with the second emitter of larger thickness by using the second screen, so that the height of the first grid line away from the surface of the substrate can be smaller, and the problem of printing offset caused by the first grid line first printed on the emitter of larger thickness away from the surface of the substrate can be avoided, which causes the second screen to be set at a higher height when printing the second grid line, so that the distance between the second screen and the emitter of smaller thickness is larger. That is, in the embodiment of the present disclosure, when the second grid line is printed by using the second screen, the distance between the second screen and the second emitter can be smaller, which is conducive to the second screen aligning the second emitter with the second emitter to print the second grid line, thereby improving the reliability of preparing the back contact battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] One or more embodiments are exemplarily illustrated by pictures in the corresponding drawings, and these exemplified descriptions do not constitute a limitation on the embodiments. Unless otherwise specified, the pictures in the drawings do not constitute a scale limitation. In order to more clearly illustrate the embodiments of the present disclosure or the technical solutions in the traditional technology, the drawings required for use in the embodiments are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present disclosure. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0019] Figure 1 A schematic diagram of the structure of a back contact battery in the related art; Figure 2 A schematic structural diagram of forming a first emitter in a method for preparing a solar cell provided in an embodiment of the present disclosure; Figure 3 A schematic diagram of the structure of removing the spacer region and the first emitter on the second region in the method for preparing a solar cell provided in an embodiment of the present disclosure; Figure 4 A schematic diagram of a structure for forming a second emitter in a method for preparing a solar cell provided in an embodiment of the present disclosure; Figure 5 A schematic diagram of the structure of removing the spacer region and the second emitter on the first region in the method for preparing a solar cell provided in an embodiment of the present disclosure; Figure 6 A schematic diagram of the structure of forming a first passivation layer in the method for preparing a solar cell provided in an embodiment of the present disclosure; Figure 7 A schematic diagram of a structure for forming a first grid line in a method for preparing a solar cell provided in an embodiment of the present disclosure; Figure 8 Another structural schematic diagram of forming a first grid line in the method for preparing a solar cell provided in an embodiment of the present disclosure.

[0020] Description of reference numerals: 100, substrate; 110, front side; 120, back side; 130, first region; 140, second region; 150, spacing region; 101, first emitter electrode; 102, second emitter electrode; 103, passivation film; 104, first fine gate; 200, base; 210, first surface; 220, second surface; 230, first region; 240, second region; 250, spacing region; 201, first emitter; 211, first doped silicon glass layer; 202, second emitter; 212, second doped silicon glass layer; 203, first passivation layer; 213, aluminum oxide film layer; 223, silicon nitride film layer; 204, second passivation layer; 214, aluminum oxide layer; 224, silicon nitride layer; 234, silicon oxide layer; 205, first gate line; 206, second gate line. DETAILED DESCRIPTION

[0021] Figure 1 A schematic diagram of the structure of a back contact battery in the related art.

[0022] refer to Figure 1 , a back contact cell in the related art includes: a substrate 100, a first emitter electrode 101, a second emitter electrode 102, a passivation film 103 and a first fine grid 104. The substrate 100 includes a front surface 110 and a back surface 120 opposite to each other; the back surface 120 is provided with first regions 130 and second regions 140 arranged alternately, and a spacing region 150 located between the first regions 130 and the second regions 140. The first emitter electrode 101 is located on the first region 130, the second emitter electrode 102 is located on the second region 140, the passivation film 103 is located on the surface of the first emitter electrode 101 and the second emitter electrode 102 away from the substrate 100, and the passivation film 103 is also located on the spacing region 150. The first fine grid 104 is located on the first region 130 and is in electrical contact with the first emitter electrode 101.

[0023] The thickness of the first emitting electrode 101 is greater than that of the second emitting electrode 102. When the first fine grid 104 is first printed on the first region 130 using the first screen, and then the second fine grid (not shown) is printed on the second region 140 using the second screen, the height H0 of the first fine grid 104 on the first emitting electrode 101 away from the surface of the substrate 100 is too high. The height H0 of the first fine grid 104 away from the surface of the substrate 100 is the height of the surface of the first fine grid 104 away from the substrate 100 relative to the back surface 120, and the height of the second screen is the height of the second screen relative to the back surface 120. The height H0 of the surface of the first fine grid 104 away from the substrate 100 will affect the setting height of the second screen. Specifically, in order to prevent the second screen from directly contacting the first fine grid 104 and damaging the first fine grid 104, the height of the second screen is higher than the first fine grid 104, that is, the first fine grid 104 with a higher height will cause the second screen to be set at a higher height, while the first fine grid 104 with a lower height can make the second screen set at a lower height. Therefore, the height H0 of the first fine grid 104 away from the surface of the substrate 100 is relatively high, so that the height of the second screen needs to be set relatively high. The high height of the second screen will cause the distance between the second screen and the passivation film 103 on the second emitter electrode 102 to be relatively large, and the second fine grid printed by the second screen will be difficult to be aligned with the second emitter electrode 102 for printing, and the slurry of the second fine grid may diffuse to other areas, introduce more charge recombination areas, or cause phenomena such as broken grids and virtual printing, thereby making the reliability of preparing back-contact batteries relatively poor.

[0024] In other words, in the related art, the first fine grid 104 is first printed on the first region 130 where the thicker emitting electrode is provided, and then the second fine grid is printed on the second region 140 where the thinner emitting electrode is provided. The first fine grid 104 first printed on the thicker emitting electrode is at a greater height away from the surface of the substrate 100, making it difficult to align the second fine grid when printing with a second screen, resulting in the reliability of preparing the back-contact battery to be improved.

[0025] Compared with the solution in the related art that the gate line is first printed on the region of the emitter with a larger thickness, resulting in the first-printed gate line being at a higher height from the surface of the substrate, in the method for preparing a back-contact battery provided in the embodiment of the present disclosure, the first gate line is first printed on the first region provided with the first emitter with a smaller thickness using a first screen, and then the second gate line is printed on the second region provided with the second emitter with a larger thickness using a second screen. The height of the first gate line on the first emitter with a smaller thickness printed first from the surface of the substrate can be smaller, so that when the second screen is used to print the second gate line, the distance between the second screen and the second emitter can be smaller, which is conducive to the second screen aligning the second emitter with the second emitter to print the second gate line, thereby facilitating the reliability of preparing the back-contact battery.

[0026] In the description of the embodiments of the present disclosure, the technical terms "first", "second", etc. are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features. In the description of the embodiments of the present disclosure, the meaning of "multiple" is more than two, unless otherwise clearly and specifically defined.

[0027] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present disclosure. The appearance of the phrase in various places in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0028] In the description of the embodiments of the present disclosure, the term "and / or" is only a description of the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B may represent: A exists, A and B exist at the same time, and B exists. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0029] In the description of the embodiments of the present disclosure, the term "multiple" refers to more than two (including two). Similarly, "multiple groups" refers to more than two groups (including two groups), and "multiple pieces" refers to more than two pieces (including two pieces).

[0030] In the description of the embodiments of the present disclosure, the orientations or positional relationships indicated by technical terms such as "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", and "circumferential" are based on the orientations or positional relationships shown in the accompanying drawings and are only for the convenience of describing the embodiments of the present disclosure and simplifying the description. They do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the embodiments of the present disclosure.

[0031] In the description of the embodiments of the present disclosure, unless otherwise clearly specified and limited, technical terms such as "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral one; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, and it can be the internal connection of two elements or the interaction relationship between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the embodiments of the present disclosure can be understood according to the specific circumstances.

[0032] In the accompanying drawings corresponding to the embodiments of the present disclosure, the thickness and area of ​​the layers are exaggerated for better understanding and ease of description. When describing a component (such as a layer, film, region, or substrate) on another component or on the surface of another component, the component may be "directly" located on the surface of the other component, or a third component may be present between the two components. On the contrary, when describing a component on the surface of another component or when another component is formed or provided on the surface of a component, it means that there is no third component between the two components. In addition, when describing a component as being "substantially" formed on another component, it means that the component is not formed on the entire surface (or front surface) of the other component, nor is it formed on a partial edge of the entire surface.

[0033] In the description of the embodiments of the present disclosure, when a component "includes" another component, unless otherwise specified, other components are not excluded, and other components may be further included. In addition, when a component such as a layer, film, region, or plate is referred to as being "on / located on" another component, it may be "directly on" the other component (i.e., located on the surface of the other component with no other components between them), or another component may exist in between. In addition, when a component such as a layer, film, region, or plate is "directly located on" another component, or when a component such as a layer, film, region, or plate is located on the surface of another component, it means that no other components are located in between.

[0034] The following will describe the various embodiments of the present disclosure in detail with reference to the accompanying drawings. However, it will be appreciated by those skilled in the art that in the various embodiments of the present disclosure, many technical details are provided in order to enable the reader to better understand the present disclosure. However, even without these technical details and various changes and modifications based on the following embodiments, the technical solutions claimed in the present disclosure can be implemented.

[0035] Figures 2 to 8 A schematic diagram of the corresponding structures formed in each step of the method for preparing a back-contact battery provided in an embodiment of the present disclosure.

[0036] Combined with reference Figures 2 to 5 The preparation method of the back contact battery includes: providing a substrate 200, the substrate 200 includes a first surface 210 and a second surface 220 opposite to each other; the second surface 220 is provided with first areas 230 and second areas 240 arranged alternately, and a spacing area 250 located between the first areas 230 and the second areas 240, a first emitter 201 is provided on the first area 230, and a second emitter 202 is provided on the second area 240, the doping element in the first emitter 201 and the doping element in the second emitter 202 have different conductivity types, and the thickness of the first emitter 201 is less than the thickness of the second emitter 202.

[0037] The substrate 200 is used to receive incident light and generate photogenerated carriers. In some embodiments, the substrate 200 may be a semiconductor substrate.

[0038] In some embodiments, the material of the substrate 200 may be an elemental semiconductor material. Specifically, the elemental semiconductor material is composed of a single element, such as silicon or germanium. The elemental semiconductor material may be in a single crystalline state, a polycrystalline state, an amorphous state, or a microcrystalline state (a state having both a single crystalline state and an amorphous state is referred to as a microcrystalline state), for example, silicon may be at least one of single crystalline silicon, polycrystalline silicon, amorphous silicon, or microcrystalline silicon.

[0039] In some embodiments, the material of the substrate 200 may also be a compound semiconductor material. Common compound semiconductor materials include but are not limited to silicon germanium, silicon carbide, gallium arsenide, indium gallium, perovskite, cadmium telluride, copper indium selenide and other materials.

[0040] The substrate 200 may also be a sapphire substrate, a silicon on insulator substrate, or a germanium on insulator substrate.

[0041] The substrate 200 may be an N-type semiconductor substrate or a P-type semiconductor substrate. The N-type semiconductor substrate is doped with an N-type doping element, which may be at least one of the V-group elements such as phosphorus (P), bismuth (Bi), antimony (Sb), or arsenic (As). The P-type semiconductor substrate is doped with a P-type element, which may be at least one of the III-group elements such as boron (B), aluminum (Al), gallium (Ga), or indium (In).

[0042] The substrate 200 includes a first surface 210 and a second surface 220 that are opposite to each other. In some embodiments, the back-contact cell is a single-sided cell, and the first surface 210 of the substrate 200 can be used as a light-receiving surface for receiving incident light, and the second surface 220 can be used as a backlight surface. In some embodiments, the back-contact cell is a double-sided cell, and the first surface 210 and the second surface 220 of the substrate 200 can both be used as light-receiving surfaces, and can both be used to receive incident light. It can be understood that the backlight surface referred to in the embodiments of the present disclosure can also receive incident light, but the degree of receiving the incident light is weaker than the degree of receiving the incident light by the light-receiving surface, and therefore is defined as a backlight surface.

[0043] Continue to refer Figures 2 to 5 The doping element in the first emitter 201 is one of a P-type doping element and an N-type doping element, and the doping element in the second emitter 202 is the other of the P-type doping element and the N-type doping element.

[0044] In some embodiments, the difference between the thickness of the first emitter 201 and the thickness of the second emitter 202 is less than or equal to 100 nm, such as 5 nm, 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 95 nm or 100 nm. The thickness of the first emitter 201 and the thickness of the second emitter 202 are within the above ranges, which can ensure that the first emitter 201 can effectively collect and transmit carriers while avoiding the situation that the second surface 220 absorbs sunlight due to the excessive thickness of the second emitter 202, or the increase of the carrier transmission path leads to a decrease in the carrier collection efficiency.

[0045] In some embodiments, the thickness of the first emitter 201 is 60 nm to 380 nm, for example, 60 nm, 80 nm, 100 nm, 150 nm, 200 nm, 250 nm, 300 nm, 350 nm, 370 nm or 380 nm, etc. The thickness of the first emitter 201 is within the above range, which can ensure that the first emitter 201 can effectively collect and transmit carriers, while also avoiding the situation that the second surface 220 absorbs sunlight due to the excessive thickness of the first emitter 201, or the increase of the carrier transmission path leads to a decrease in the carrier collection efficiency.

[0046] In some embodiments, the thickness of the second emitter 202 is 60nm to 400nm, such as 61nm, 65nm, 70nm, 80nm, 100nm, 150nm, 200nm, 250nm, 300nm, 350nm, 370nm, 390nm or 400nm. The thickness of the second emitter 202 is within the above range, which can ensure that the second emitter 202 can effectively collect and transmit carriers, and can also avoid the second surface 220 absorbing solar light due to the thickness of the second emitter 202 being too thick, or increasing the carrier transmission path to reduce the carrier collection efficiency.

[0047] In some embodiments, the ratio of the projected area of ​​the first emitter 201 on the second surface 220 to the area of ​​the second surface 220 is 0.1-0.4, such as 0.1, 0.2, 0.3 or 0.4. When the ratio of the projected area of ​​the first emitter 201 on the second surface 220 to the area of ​​the second surface 220 is within the above range, the projected area of ​​the first emitter 201 is small, which can reduce the parasitic absorption caused by the first emitter 201, thereby improving the performance of the back contact battery.

[0048] The ratio of the projected area of ​​the second emitter 202 on the second surface 220 to the area of ​​the second surface 220 is 0.1 to 0.4, for example, 0.1, 0.2, 0.3 or 0.4. When the ratio of the projected area of ​​the second emitter 202 on the second surface 220 to the area of ​​the second surface 220 is within the above range, the projected area of ​​the second emitter 202 is small, and the parasitic absorption caused by the second emitter 202 can be reduced, thereby improving the performance of the back contact battery.

[0049] In some embodiments, the width of the first emitter 201 is 150 μm to 300 μm, such as 150 μm, 180 μm, 200 μm, 220 μm, 240 μm, 250 μm, 260 μm, 280 μm or 300 μm, along the first direction X. When the width of the first emitter 201 is within the above range, the width of the first emitter 201 is small, which can reduce the parasitic absorption caused by the first emitter 201, thereby improving the performance of the back contact battery.

[0050] Along the first direction X, the width of the second emitter 202 is 150 μm to 300 μm, for example, 150 μm, 180 μm, 200 μm, 220 μm, 240 μm, 250 μm, 260 μm, 280 μm or 300 μm. When the width of the second emitter 202 is within the above range, the width of the second emitter 202 is small, which can reduce the parasitic absorption caused by the second emitter 202, thereby improving the performance of the back contact battery.

[0051] The first direction X is the direction from the first emitter 201 to the second emitter 202 .

[0052] Combined with reference Figure 2 and Figure 3 In some embodiments, the step of forming the first emitter 201 may include: depositing a first crystalline silicon layer (not shown) on the second surface 220; performing a doping treatment on the first crystalline silicon layer to convert the first crystalline silicon layer into the first emitter 201 and forming a first doped silicon glass layer 211 on the surface of the first emitter 201 away from the substrate 200; and removing the first doped silicon glass layer 211 and the first emitter 201 on the spacer 250 and the second region 240.

[0053] The material of the first crystalline silicon layer can be polycrystalline silicon or amorphous silicon.

[0054] The first crystalline silicon layer may be formed by chemical vapor deposition.

[0055] The doping process includes a high temperature diffusion method or an ion implantation method.

[0056] In some embodiments, the first doped silicon glass layer 211 may be a borosilicate glass layer or a phosphosilicate glass layer, where "boron" or "phosphorus" depends on the doping element during the doping process of forming the first emitter 201. For example, if the doping element is boron, the first doped silicon glass layer 211 is a borosilicate glass layer.

[0057] In some embodiments, the thickness of the first doped silicon glass layer 211 is 20 nm to 80 nm, such as 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm or 80 nm.

[0058] In some embodiments, the method for removing the first doped silicon glass layer 211 and the first emitter 201 on the spacer 250 and the second region 240 may be: using a laser process to transform the first doped silicon glass layer 211 on the spacer 250 and the second region 240 into a first loose structure; and then using wet etching to remove the first loose structure and the first emitter 201 on the spacer 250 and the second region 240. The laser process transforms the first doped silicon glass layer 211 on the spacer 250 and the second region 240 into the first loose structure, so that the subsequent wet etching can remove the first loose structure and the first emitter 201 on the spacer 250 and the second region 240. The first emitter 201 on the first region 230 is retained under the protection of the first doped silicon glass layer 211 on the first region 230 that has not been subjected to the laser process.

[0059] refer to Figure 3 and Figure 4 In some embodiments, the step of forming the second emitter 202 may include: forming a second crystalline silicon layer (not shown) on the surface of the first doped silicon glass layer 211 in the first region 230 away from the substrate 200, and on the second region 240 and the spacer region 250; performing a doping treatment on the second crystalline silicon layer to convert the second crystalline silicon layer into the second emitter 202 and forming a second doped silicon glass layer 212 on the surface of the second emitter 202 away from the substrate 200; and removing the second doped silicon glass layer 212 and the second emitter 202 on the spacer region 250 and the first region 230.

[0060] The material of the second crystalline silicon layer can be polycrystalline silicon or amorphous silicon.

[0061] The second crystalline silicon layer may be formed by chemical vapor deposition.

[0062] The doping process includes a high temperature diffusion method or an ion implantation method.

[0063] In some embodiments, the second doped silicon glass layer 212 may be a borosilicate glass layer or a phosphosilicate glass layer, where "boron" or "phosphorus" depends on the doping element during the doping process to form the second emitter 202. For example, if the doping element is phosphorus, the second doped silicon glass layer 212 is a phosphosilicate glass layer.

[0064] In some embodiments, the thickness of the second doped silicon glass layer 212 is 20 nm to 80 nm, such as 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm or 80 nm.

[0065] In some embodiments, the method for removing the second doped silicon glass layer 212 and the second emitter 202 on the spacer region 250 and the first region 230 includes: using a laser process to transform the second doped silicon glass layer 212 on the spacer region 250 and the first region 230 into a second loose structure; and wet etching to remove the second loose structure and the second emitter 202 located on the spacer region 250 and the first region 230.

[0066] In some embodiments, when the first emitter 201 and the second emitter 202 are formed on the second surface 220, a wrap-around coating layer (not shown) is formed on the first surface 210 and the side surface of the substrate 200, and the wrap-around coating layer at least includes the first emitter 201 and the second emitter 202. The method for preparing a back contact cell also includes: removing the wrap-around coating layer. In this way, it is avoided that an additional recombination center is added to the substrate 200 due to the wrap-around coating layer, which affects the performance of the back contact cell.

[0067] The method for removing the coating layer may be acid wet etching.

[0068] refer to Figure 5 In some embodiments, the method for preparing the back contact cell may further include: performing a texturing process on the spacer 250 of the second surface 220 and the first surface 210 to form a velvet structure on the spacer 250 of the second surface 220 and the first surface 210. The velvet structure can increase the number of refractions of light on the surface of the back contact cell, which is beneficial to the absorption of light by the back contact cell, thereby improving the performance of the back contact cell.

[0069] Among them, the first doped silicon glass layer 211 on the first area 230 and the second doped silicon glass layer 212 on the second area 240 will protect the first emitter 201 and the second emitter 202 so that the texturing treatment will not damage the first emitter 201 and the second emitter 202, and no film layer is set on the spacer area 250 and the first surface 210. Under the texturing treatment, the first surface 210 and the spacer area 250 will form a velvet structure.

[0070] In some embodiments, a solution texturing method can be used to prepare a velvet structure. For example, if the substrate 200 is single crystal silicon, a mixed solution of an alkali solution and an alcohol solution can be used to texturize the surface of the substrate 200; if the substrate 200 is polycrystalline silicon, an acid solution can be used to texturize the surface of the substrate 200.

[0071] In some embodiments, the textured structure may be prepared by using a laser texturing process or a reactive ion etching (RIE) process.

[0072] Combined with reference Figure 5 and Figure 6 In some embodiments, the method for preparing a back contact cell may further include: removing the first doped silicon glass layer 211 and the second doped silicon glass layer 212. Specifically, a mask may be provided on the spacer 250 to protect the substrate 200 of the spacer 250, and the first doped silicon glass layer 211 and the second doped silicon glass layer 212 may be removed by wet etching, and finally the mask may be removed. Removing the first doped silicon glass layer 211 and the second doped silicon glass layer 212 may avoid the compound problem caused by the first doped silicon glass layer 211 and the second doped silicon glass layer 212, which is beneficial to improving the performance of the back contact cell.

[0073] In some other embodiments, the first doped silicon glass layer and the second doped silicon glass layer may not be removed.

[0074] refer to Figure 6 In some embodiments, the method for preparing a back-contact battery may further include: forming a first passivation layer 203 on the second surface 220 ; the first passivation layer 203 is located on the surface of the first emitter 201 and the second emitter 202 away from the substrate 200 , and is also located on the spacer area 250 of the second surface 220 .

[0075] The first passivation layer 203 is used to passivate the second surface 220 of the substrate 200 to reduce the surface recombination of the second surface 220 and improve the collection efficiency of carriers, thereby improving the photoelectric conversion efficiency of the back contact cell.

[0076] The first passivation layer 203 may be formed by atomic layer deposition or chemical vapor deposition.

[0077] The first passivation layer 203 may be a single-layer structure or a stacked-layer structure, and the material of the first passivation layer 203 may be one or more of silicon oxide, silicon nitride, silicon oxynitride, silicon carbonitride oxide, titanium oxide, hafnium oxide, aluminum oxide, and the like.

[0078] In some embodiments, the first passivation layer 203 includes an aluminum oxide film layer 213 and a silicon nitride film layer 223. The silicon nitride film layer 223 is located on a surface of the aluminum oxide film layer 213 facing away from the substrate 200.

[0079] Continue to refer Figure 6 In some embodiments, the method for preparing a back-contact battery may further include: forming a second passivation layer 204 on the first surface 210 .

[0080] The second passivation layer 204 is used to passivate the first surface 210 of the substrate 200 to reduce the surface recombination of the first surface 210 and improve the collection efficiency of carriers, thereby improving the photoelectric conversion efficiency of the back contact cell.

[0081] The second passivation layer 204 may be formed by atomic layer deposition or chemical vapor deposition.

[0082] The second passivation layer 204 may be a single-layer structure or a stacked-layer structure, and the material of the second passivation layer 204 may be one or more of silicon oxide, silicon nitride, silicon oxynitride, silicon carbonitride oxide, titanium oxide, hafnium oxide, aluminum oxide, and the like.

[0083] In some embodiments, the second passivation layer 204 includes an aluminum oxide layer 214, a silicon nitride layer 224, and a silicon oxide layer 234. The aluminum oxide layer 214 is located between the substrate 200 and the silicon nitride layer 224, and the silicon nitride layer 224 is located between the aluminum oxide layer 214 and the silicon oxide layer 234.

[0084] Combined with reference Figures 6 to 8 The method for preparing a back-contact battery also includes: using a first screen to print a first gate line 205 on a first area 230 of a second surface 220, the first gate line 205 is in electrical contact with a first emitter 201; using a second screen to print a second gate line 206 on a second area 240 of the second surface 220, the second gate line 206 is in electrical contact with a second emitter 202.

[0085] The first gate line 205 is formed by printing metal paste on the first area 230 using a first screen.

[0086] In some embodiments, the metal paste may include at least one of silver, aluminum, copper, tin, gold, lead, or nickel.

[0087] In some embodiments, the metal paste contains materials with high corrosive components such as glass. Thus, during the sintering process, the corrosive components will corrode the first passivation layer 203 and the first emitter 201, thereby allowing the metal paste to penetrate the first passivation layer 203 and a portion of the first emitter 201, so that the metal paste burns through the side of the first emitter 201 away from the substrate 200 to a portion of the thickness of the first emitter 201, thereby forming a first gate line 205.

[0088] A second gate line 206 is formed by printing metal paste on the second area 240 using a second screen.

[0089] In some embodiments, the metal paste may include at least one of silver, aluminum, copper, tin, gold, lead, or nickel.

[0090] In some embodiments, the metal paste contains materials with high corrosive components such as glass. Thus, during the sintering process, the corrosive components will corrode the first passivation layer 203 and the second emitter 202, thereby allowing the metal paste to penetrate the first passivation layer 203 and a portion of the second emitter 202, so that the metal paste burns through from the side of the second emitter 202 away from the substrate 200 to a portion of the thickness of the second emitter 202, thereby forming a second gate line 206.

[0091] The height of the surface of the first gate line 205 away from the substrate 200 relative to the second surface 220 is a first height H1 , and the height of the surface of the first passivation layer 203 on the second region 240 away from the substrate 200 relative to the second surface 220 is a second height H2 .

[0092] Combined with reference Figure 6 and Figure 7 In some embodiments, the first height H1 may be greater than the second height H2, and the difference between the first height H1 and the second height H2 is less than or equal to 4 μm, such as 0.5 μm, 1 μm, 2 μm, 3 μm or 4 μm. When the difference is within this range, it can be avoided that when printing the second gate line 206, the first height H1 of the first gate line 205 is too large, and the height of the second screen relative to the second surface 220 needs to be set too high, so that the distance between the second screen and the first passivation layer 203 on the second emitter 202 is too large, making it difficult for the second screen to align and print the second gate line 206. In other words, when the difference between the first height H1 and the second height H2 is within the above range, it can be ensured that when printing the second gate line 206, the distance between the second screen and the first passivation layer 203 on the second emitter 202 is small, so that the second screen is easy to align with the second emitter 202 to print the second gate line 206.

[0093] Combined with reference Figure 6 and Figure 8 In some embodiments, the first height H1 may be equal to the second height H2. Thus, when the second gate line 206 is printed using the second screen, the first gate line 205 lifts up the second screen, resulting in a large distance between the second screen and the first passivation layer 203 on the second emitter 202, which may cause difficulty in alignment printing.

[0094] In some embodiments, the thickness of the first gate line 205 is less than the thickness of the second gate line 206. That is, the thickness of the first gate line 205 is small, and the thickness of the first gate line 205 is positively correlated with the first height H1 of the first gate line 205. The first gate line 205 with a small thickness allows the first height H1 of the first gate line 205 to be small, so that the height of the second screen relative to the second surface 220 can be small, so that when the second screen is used to print the second gate line 206, the distance between the second screen and the first passivation layer 203 on the second emitter 202 can be small, which is conducive to the second screen aligning the second emitter 202 to print the second gate line 206, thereby improving the reliability of preparing the back contact battery.

[0095] In some embodiments, the thickness of the first gate line 205 is 2 μm to 20 μm, for example, 2 μm, 4 μm, 5 μm, 8 μm, 10 μm, 11 μm, 12 μm, 15 μm or 20 μm. When the thickness of the first gate line 205 is within the above range, the thickness of the first gate line 205 is small, and the first gate line 205 with a small thickness can make the first height H1 smaller, thereby making the height of the second screen relative to the second surface 220 smaller, so that when the second screen is used to print the second gate line 206, the distance between the second screen and the first passivation layer 203 on the second emitter 202 can be small, which is conducive to the second screen aligning the second emitter 202 to print the second gate line 206, thereby improving the reliability of preparing the back contact battery.

[0096] In some embodiments, the thickness of the second gate line 206 is 5 μm to 30 μm, for example, 5 μm, 8 μm, 10 μm, 12 μm, 15 μm, 18 μm, 20 μm, 25 μm or 30 μm. When the thickness of the second gate line 206 is within the above range, the thickness of the second gate line 206 can be larger, and the second gate line 206 can provide a larger current transmission channel, thereby improving the efficiency of the second gate line 206 in collecting current.

[0097] In the method for preparing the back contact battery provided above, the first gate line 205 is first printed on the first area 230 provided with the first emitter 201 having a smaller thickness using the first screen, and then the second gate line 206 is printed on the second area 240 provided with the second emitter 202 having a larger thickness using the second screen. The height of the first gate line 205 on the first emitter 201 having a smaller thickness printed first away from the surface of the substrate 200 can be smaller, so that when the second screen is used to print the second gate line 206, the distance between the second screen and the second emitter 202 can be smaller, which is conducive to aligning the second screen with the second emitter 202 to print the second gate line 206, thereby facilitating the reliability of preparing the back contact battery.

[0098] Correspondingly, another aspect of the present disclosure also provides a back contact battery prepared by the method for preparing a back contact battery of any of the above embodiments. It should be noted that the parts that are the same or corresponding to the above embodiments can refer to the corresponding description of the above embodiments, and will not be repeated below.

[0099] Combined with reference Figures 6 to 8 The back contact cell comprises: a substrate 200, the substrate 200 comprises a first surface 210 and a second surface 220 opposite to each other; the second surface 220 is provided with first regions 230 and second regions 240 arranged alternately, and a spacer region 250 located between the first regions 230 and the second regions 240; the first region 230 is provided with a first emitter 201, the second region 240 is provided with a second emitter 202, the doping element in the first emitter 201 and the doping element in the second emitter 202 have different conductivity types, and the thickness of the first emitter 201 is less than the thickness of the second emitter 202. The back contact cell further comprises a first gate line 205 and a second gate line 206, the first gate line 205 is located on the first region 230 and is in electrical contact with the first emitter 201; the second gate line 206 is located on the second region 240 and is in electrical contact with the second emitter 202.

[0100] Those skilled in the art can understand that the above-mentioned embodiments are specific examples for realizing the present disclosure, and in practical applications, various changes can be made to them in form and details without departing from the spirit and scope of the present disclosure. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present disclosure, so the protection scope of the present disclosure shall be based on the scope defined in the claims.

Claims

1. A method for preparing a back contact battery, characterized in that: include: A substrate is provided, wherein the substrate comprises a first surface and a second surface opposite to each other; the second surface is provided with first regions and second regions arranged alternately, and a spacing region located between the first regions and the second regions, a first emitter is provided on the first region, a second emitter is provided on the second region, a doping element in the first emitter and a doping element in the second emitter have different conductivity types, and a thickness of the first emitter is less than a thickness of the second emitter; Printing a first gate line on the first region of the second surface using a first screen, wherein the first gate line is in electrical contact with the first emitter; A second gate line is printed on the second region of the second surface using a second screen, wherein the second gate line is in electrical contact with the second emitter.

2. The method for preparing a back contact battery according to claim 1, characterized in that: Before printing the first gate line, the method for preparing the back-contact battery also includes: forming a first passivation layer, the first passivation layer is located on the surface of the first emitter and the second emitter away from the substrate, and is also located on the spacing area of ​​the second surface; the height of the surface of the first gate line away from the substrate relative to the second surface is a first height, the height of the surface of the first passivation layer on the second area away from the substrate relative to the second surface is a second height, the first height is greater than the second height, and the difference between the first height and the second height is less than or equal to 4μm.

3. The method for preparing a back contact battery according to claim 1, characterized in that: Before printing the first gate line, the method for preparing the back-contact battery also includes: forming a first passivation layer, the first passivation layer is located on the surface of the first emitter and the second emitter facing away from the substrate, and is also located on the spacing area of ​​the second surface; the height of the surface of the first gate line facing away from the substrate relative to the second surface is a first height, the height of the surface of the first passivation layer on the second area facing away from the substrate relative to the second surface is a second height, and the first height is equal to the second height.

4. The method for preparing a back contact battery according to claim 1, characterized in that: A difference between a thickness of the first emitter and a thickness of the second emitter is less than or equal to 100 nm.

5. The method for preparing a back contact battery according to claim 4, characterized in that: The thickness of the first emitter is 60nm-380nm, and the thickness of the second emitter is 60nm-400nm.

6. The method for preparing a back contact battery according to claim 1, characterized in that: The thickness of the first gate line is smaller than the thickness of the second gate line.

7. The method for preparing a back contact battery according to claim 6, characterized in that: The thickness of the first gate line is 2 μm-20 μm, and the thickness of the second gate line is 5 μm-30 μm.

8. The method for preparing a back contact battery according to any one of claims 1 to 7, characterized in that: The ratio of the projection area of ​​the first emitter on the second surface to the area of ​​the second surface is 0.1-0.4, and the ratio of the projection area of ​​the second emitter on the second surface to the area of ​​the second surface is 0.1-0.

4.

9. The method for preparing a back contact battery according to claim 8, characterized in that: Along the first direction, the width of the first emitter is 150 μm-300 μm, and the width of the second emitter is 150 μm-300 μm.

10. A back contact battery, characterized in that: include: A substrate, the substrate comprising a first surface and a second surface opposite to each other; the second surface is provided with first areas and second areas arranged alternately, and a spacing area located between the first areas and the second areas, the first area is provided with a first emitter, the second area is provided with a second emitter, the doping element in the first emitter and the doping element in the second emitter have different conductivity types, and the thickness of the first emitter is less than the thickness of the second emitter; a first gate line, the first gate line being located on the first region and electrically contacting the first emitter; A second gate line is located on the second region and is electrically connected to the second emitter.

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