Back contact battery
By setting markers with varying heights on the back of the silicon substrate, the problem of insufficient printing precision in the new battery structure was solved, enabling precise alignment printing, improving the production yield of solar cells and reducing production costs.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- HUAIAN JIETAI NEW ENERGY TECHNOLOGY CO LTD
- Filing Date
- 2025-05-30
- Publication Date
- 2026-05-01
AI Technical Summary
In existing technologies, during the electrode printing process of novel battery structures such as TOPCon and xBC, the contrast difference between the marked area and the normal area is insufficient, resulting in inaccurate positioning and reduced product yield.
A first and a second marker with a height difference are set on the back side of the silicon substrate. The height difference between the first and the second markers is 0 < D ≤ 3 μm, and their morphological differences are obvious. By forming a significant contrast difference between the smooth polished surface and the pyramid textured surface, it is possible to accurately identify and align the printing.
This improved the printing accuracy and yield rate in battery production, reduced production costs, and ensured that the appearance and performance of the finished battery products remained unaffected.
Smart Images
Figure CN224192340U_ABST
Abstract
Description
A back contact battery Technical Field
[0001] This utility model relates to the field of solar cell technology, specifically to a back contact battery. Background Technology
[0002] In the solar cell industry, as the number of electrodes in solar cells increases and their structures and technologies become more complex, precise registration during electrode printing becomes crucial. The emergence of new cell structures such as TOPCon and xBC places even higher demands on the precision required in the production process. Laser marking technology can accurately mark points on the complex surface of solar cells, providing a reliable reference for subsequent processing and inspection, thus meeting the production needs of these new cell structures.
[0003] Laser marking can improve production efficiency and accuracy. Specifically, laser marking can provide precise positioning information for automated equipment, ensuring the accurate execution of each process and improving production efficiency and consistency. For example, in the welding and packaging of battery cells, precise markings can help the equipment quickly and accurately locate the welding and packaging positions, reducing errors and rework.
[0004] For xBC products, the full back-side patterning requires higher precision. Multiple laser processes are needed during manufacturing to assist in patterning and wafer positioning. However, ordinary lasers cannot create a contrast difference between the marked area and the normal area, which results in lower recognition accuracy during the printing and overprinting process, easily leading to inaccurate positioning and reduced product yield. Summary of the Invention
[0005] To address the aforementioned technical problems, this utility model provides a back-contact battery that accurately and effectively identifies the marking points by creating a clear difference between the marked and non-marked areas, thereby improving the alignment accuracy of the battery manufacturing printing process.
[0006] The present invention adopts the following technical solution:
[0007] A back-contact battery, comprising:
[0008] A silicon substrate having a front and a back side that are positioned opposite to each other;
[0009] A front passivation layer is disposed on the front side of the silicon substrate;
[0010] A first region and a second region are alternately disposed on the back side of the silicon substrate; the first region sequentially includes a first tunneling oxide layer, a first doped polysilicon layer, a back passivation layer, and a first metal electrode along the direction away from the silicon substrate, wherein the first doped polysilicon layer is in ohmic contact with the first metal electrode; the second region sequentially includes a second tunneling oxide layer, a second doped polysilicon layer, a back passivation layer, and a second metal electrode along the direction away from the silicon substrate, wherein the second doped polysilicon layer is in ohmic contact with the second metal electrode;
[0011] An isolation region located between the first region and the second region, the isolation region being recessed inward and closer to the silicon substrate relative to the first region and the second region;
[0012] The back side of the silicon substrate is provided with a first marker point and a second marker point for alignment printing. The second marker point wraps around the first marker point or the first marker point wraps around the second marker point. The height difference D between the first marker point and the second marker point satisfies 0 < D ≤ 3, and the unit is μm.
[0013] Furthermore, the height difference between the first marker point and the second marker point is 0.5μm~2.5μm.
[0014] Furthermore, the first marking point is a polished surface, and the second marking point is a velvety surface.
[0015] Furthermore, the reflectivity of the first marker point is 30% to 40%, and the reflectivity of the second marker point is less than 15%.
[0016] Furthermore, when the second marker encompasses the first marker, the area of the first marker is 20% to 85% of the area of the second marker.
[0017] When the first marker point encloses the second marker point, the area of the second marker point is 20% to 85% of the area of the first marker point.
[0018] Furthermore, the shapes of the first and second markers can be any one of a cross, a circle, a triangle, a quadrilateral, or a hexagon.
[0019] This utility model has the following beneficial effects:
[0020] (1) The back contact battery of this utility model, by setting a first marking point and a second marking point with a height difference on the back of the silicon substrate, facilitates effective and accurate identification, provides a guarantee for the printing accuracy of subsequent overprinting, can improve the yield of solar cell production and reduce production costs.
[0021] (2) In the back contact battery of this utility model, the first marking point and the second marking point are further set to have a textured surface and a polished surface respectively, based on the height difference, so as to form a significant difference in appearance, further improve the recognition accuracy and improve the printing yield. Attached Figure Description
[0022] To more clearly illustrate the technical solutions of the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0023] Figure 1 is a cross-sectional schematic diagram of the back contact battery structure of this utility model;
[0024] Figure 2 is a top view of the structure of the first and second marking points in one embodiment of the back contact battery of this utility model.
[0025] Figure 3 is a cross-sectional view of the first and second marking points in one embodiment of the back contact battery of this utility model.
[0026] Figure 4 is a top view of the structure of the first and second marking points in another embodiment of the back contact battery of this utility model.
[0027] Figure 5 is a cross-sectional view of the first and second marking points in another embodiment of the back contact battery of this utility model.
[0028] Figure 6 is a scanning electron microscope image of the polished surface in the back contact battery of this utility model;
[0029] Figure 7 is a scanning electron microscope image of the textured surface in the back contact battery of this utility model;
[0030] In the figure: 1-Silicon substrate, 2-Front passivation layer, 3-First region, 4-Second region, 5-First tunneling oxide layer, 6-First doped polysilicon layer, 7-Back passivation layer, 8-First metal electrode, 9-Second tunneling oxide layer, 10-Second doped polysilicon layer, 11-Second metal electrode, 12-Isolation region, 13-First marker point, 14-Second marker point. Detailed Implementation
[0031] The technical solutions of this utility model will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only some embodiments of this utility model, and not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this utility model.
[0032] The marking point referred to in this utility model, also called a marker point or Mark point, refers to a closed area with certain characteristics within a certain range.
[0033] In a first aspect, this utility model provides a back contact battery, as shown in Figures 1-7, comprising:
[0034] Silicon substrate 1 has a front side and a back side that are positioned opposite to each other;
[0035] A front passivation layer 2 is disposed on the front side of the silicon substrate;
[0036] A first region 3 and a second region 4 are alternately disposed on the back side of the silicon substrate; the first region 3 includes, in sequence along the direction away from the silicon substrate, a first tunneling oxide layer 5, a first doped polysilicon layer 6, a back passivation layer 7, and a first metal electrode 8, wherein the first doped polysilicon layer 6 is in ohmic contact with the first metal electrode 8; the second region 4 includes, in sequence along the direction away from the silicon substrate, a second tunneling oxide layer 9, a second doped polysilicon layer 10, a back passivation layer 7, and a second metal electrode 11, wherein the second doped polysilicon layer 10 is in ohmic contact with the second metal electrode 11;
[0037] An isolation region 12 is located between the first region 3 and the second region 4. The isolation region 12 is recessed inward and is closer to the silicon substrate 1 than the first region 3 and the second region 4.
[0038] The back side of the silicon substrate is provided with a first marking point 13 and a second marking point 14 for alignment printing. The second marking point 14 wraps around the first marking point 13 or the first marking point 13 wraps around the second marking point 14. The height difference D between the first marking point 13 and the second marking point 14 satisfies 0 < D ≤ 3, and the unit is μm.
[0039] This invention's back-contact battery, on the one hand, reduces the thickness of the isolation area, thus mitigating parasitic absorption and other problems caused by excessively thick polycrystalline silicon layers; on the other hand, by setting a first and second marker point with a height difference, a significant brightness difference is created between them, facilitating precise alignment during printing and ensuring printing accuracy in subsequent overprinting. This improves the yield rate of solar cell production and reduces production costs. The height difference also creates a significant contrast difference between the marker points in 3D, which is more conducive to gripping and results in better printing accuracy compared to marker points set only on a flat surface.
[0040] The first and second marking points of this invention enable precise alignment and printing of electrodes in the early stages of battery manufacturing, which helps improve the yield rate of batteries. Furthermore, unlike marking points in existing technologies used for tracking finished battery cells, the marking points in the batteries manufactured using this invention are completely covered after precise alignment and printing, without affecting the appearance or application of the final battery product.
[0041] Specifically, in some embodiments of this invention, the height difference between the first and second marker points is 0.1 μm, 0.2 μm, 0.3 μm, 0.4 μm, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1 μm, 1.2 μm, 1.4 μm, 1.5 μm, 1.6 μm, 1.8 μm, 2 μm, 2.2 μm, 2.4 μm, 2.5 μm, 2.6 μm, 2.8 μm, 3 μm, or any value between two of these ranges; preferably, the height difference between the first and second marker points is 0.5 μm to 2.5 μm. If the height difference is too large, it increases the difficulty of subsequent processes and production costs, adversely affecting the performance of the finished battery. In this invention, the height difference between the first and second marker points is obtained by testing with an Olympus semiconductor microscope or other microscopic morphology instruments.
[0042] Specifically, in some embodiments of this utility model, as shown in Figures 2-5, the first marking point 13 is a polished surface and the second marking point 14 is a velvety surface; the smooth polished surface and the pyramidal velvety surface structure have significant differences in morphology, and combined with the height difference, the alignment accuracy can be further improved, and precise printing can be achieved.
[0043] The first doped polysilicon layer and the second doped polysilicon layer have opposite doping types.
[0044] Specifically, in some embodiments of this utility model, the first doped polysilicon layer is a P-type doped polysilicon layer, and the second doped polysilicon layer is an N-type doped polysilicon layer; the first metal electrode is a positive metal electrode, and the second metal electrode is a negative metal electrode; the P-type doped polysilicon layer forms an ohmic contact with the positive metal electrode, and the N-type doped polysilicon layer forms an ohmic contact with the negative metal electrode.
[0045] In another embodiment of this utility model, the first doped polysilicon layer is an N-type doped polysilicon layer, and the second doped polysilicon layer is a P-type doped polysilicon layer; the first metal electrode is a metal negative electrode, and the second metal electrode is a metal positive electrode; the P-type doped polysilicon layer forms an ohmic contact with the metal positive electrode, and the N-type doped polysilicon layer forms an ohmic contact with the metal negative electrode.
[0046] Specifically, in some embodiments of this invention, the reflectivity of the first marker point is 30%~40%, and the reflectivity of the second marker point is less than 15%. Precise alignment is achieved by creating a significant contrast difference between the first and second marker points.
[0047] Specifically, in some embodiments of this utility model, when the second marker point encloses the first marker point, the area of the first marker point is 20% to 85% of the area of the second marker point; when the first marker point encloses the second marker point, the area of the second marker point is 20% to 85% of the area of the first marker point. By limiting the area ratio of the first marker point and the second marker point, the indistinguishability between the first marker point and the second marker point is prevented due to the first marker point being too large or too small. The area of the marker point referred to in this utility model, as shown in Figures 3 and 5, represents the area of the closed shape formed by two quadrilaterals.
[0048] Specifically, as some embodiments of this utility model, the first and second marking points are any one of the following shapes: cross, circle, triangle, quadrilateral, and hexagon. More specifically, the first and second marking points have the same shape.
[0049] This utility model also provides a method for preparing the above-mentioned back contact battery, including the following steps:
[0050] (1) Polishing the silicon substrate;
[0051] (2) A first tunneling oxide layer and a first polysilicon layer are sequentially formed on the back side of the silicon substrate, the first polysilicon layer is doped to form a first doped polysilicon layer, and a first mask layer is formed on the surface of the first doped polysilicon layer.
[0052] (3) Perform first laser processing on the second region and the first marker point to remove or thin the first mask layer, and then use a wet etching process to thin the first laser processing area. The first marker point has a height difference with the first region and the second region.
[0053] (4) A second tunneling oxide layer and a second polysilicon layer are sequentially formed on the back side of the silicon substrate, the second polysilicon layer is doped to form a second doped polysilicon layer, and a second mask layer is formed on the surface of the second doped polysilicon layer.
[0054] (5) Perform a second laser treatment on the first region, the second marker point, and the isolation region to remove or thin the second mask layer, and then use a secondary wet etching process to thin the second laser treatment region. The first marker point and the second marker point have a height difference.
[0055] (6) Remove the remaining first and second mask layers;
[0056] (7) Texturing the front side and isolation area of the silicon substrate to form a pyramid textured surface;
[0057] (8) Deposit passivation layers on the front and back sides of the silicon substrate to form a front passivation layer and a back passivation layer;
[0058] (9) A first metal electrode is printed in a first region on the back side of a silicon substrate, and a second metal electrode is printed in a second region. After sintering, the first metal electrode forms an ohmic contact with the first doped polysilicon layer, and the second metal electrode forms an ohmic contact with the second doped polysilicon layer.
[0059] In the preparation method of the back contact battery of this utility model, during the preparation of the first region and the second region, a first marker point and a second marker point with height are formed on the back side of the silicon substrate. Specifically, in some embodiments of this utility model, the first marker point is located in the first region. In step (3), the first marker point is thinned to form a height difference between the first marker point and other positions in the first region, which facilitates the gripping of the second laser processing in the subsequent step (5) and helps to form a second marker point around the first marker point. At the same time, after the second marker point is gripped in step (5), it is thinned to form a height difference between the first marker point and the second marker point. Through the height difference, it helps to achieve accurate alignment during the printing of metal electrodes in step (9) and improve the yield of back contact battery products.
[0060] The formation of the first and second marker points in this invention is performed before the deposition of the passivation layer, which does not damage the passivation layer and does not affect the passivation performance of the battery. Furthermore, the first and second marker points are obtained by creating a height difference during the thinning process in the first region, second region, or isolation region, without damaging the silicon substrate.
[0061] Specifically, in some embodiments of this utility model, step (7) further includes texturing the second marker point to form a pyramidal textured surface. In order to further improve the contrast between the first marker point and the second marker point, the second marker point is texturized in step (7) so that the pyramidal textured surface structure of the second marker point and the planar polished structure of the first marker point form a significant morphological difference; the first marker point and the second marker point produce a significant contrast difference through the height difference and morphological difference, which further improves the alignment accuracy during the printing process.
[0062] Specifically, in some embodiments of this utility model, the laser spot size of the first laser processing in step (3) is 50μm~550μm, and the single-pulse energy density of the laser is 80mJ / cm². 2 ~500mJ / cm 2 The laser single-pulse energy density of the first marker point is less than that of the laser single-pulse energy density of the second region.
[0063] In step (5), the laser spot size of the second laser processing step is 50μm~550μm, and the single-pulse energy density of the laser is 80mJ / cm². 2 ~500mJ / cm 2 The laser single-pulse energy density at the second marker point is less than the laser single-pulse energy density in the isolation area outside the second marker point.
[0064] More specifically, the laser spot size is within the range of 50μm, 60μm, 80μm, 100μm, 120μm, 150μm, 180μm, 200μm, 220μm, 250μm, 280μm, 300μm, 320μm, 350μm, 380μm, 400μm, 420μm, 450μm, 480μm, 500μm, 520μm, 550μm, or any combination thereof; the single-pulse energy density of the laser is 80mJ / cm². 2 100mJ / cm 2 120mJ / cm 2 150mJ / cm 2 180mJ / cm 2 200mJ / cm 2 240mJ / cm 2 270mJ / cm 2 300mJ / cm 2 320mJ / cm 2 350mJ / cm 2 380mJ / cm 2 400mJ / cm 2 420mJ / cm 2 450mJ / cm 2 480mJ / cm 2 500mJ / cm 2 Or a range of values consisting of either of the two.
[0065] Specifically, in some embodiments of this utility model, the single wet etching process involves reacting an alkaline solution with a concentration of 5% to 10% and a protective additive with 0.5% to 1% at 80°C to 88°C for 100 to 320 seconds.
[0066] The secondary wet etching process involves reacting a 1% to 5% alkaline solution and a 0.5% to 1% protective additive at 70°C to 80°C for 500 to 700 seconds.
[0067] More specifically, in a single wet etching process, NaOH or KOH is used for the reaction; the concentration of the alkali solution is 5%, 6%, 7%, 8%, 9%, 10%, or any value between the two; the concentration of the protective additive is 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, or any value between the two; the reaction temperature is 80℃, 82℃, 83℃, 84℃, 85℃, 86℃, 87℃, 88℃, or any value between the two; and the reaction time is 100s, 120s, 150s, 180s, 200s, 240s, 270s, 300s, 320s, or any value between the two.
[0068] In the secondary wet etching process, NaOH or KOH is used for the reaction; the concentration of the alkali solution is 1%, 2%, 3%, 4%, 5%, or any value between the two; the concentration of the protective additive is 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, or any value between the two; the reaction temperature is 70℃, 72℃, 73℃, 74℃, 75℃, 76℃, 77℃, 78℃, 80℃, or any value between the two; the reaction time is 500s, 520s, 550s, 580s, 600s, 620s, 640s, 650s, 670s, 680s, 700s, or any value between the two.
[0069] This invention controls the thinning range through a mask + laser processing + wet etching process, thereby controlling the height difference of different structures. By controlling the laser single-pulse energy density of the first marker point to be less than that of the second region before wet etching, the thinning range of the second region in step (3) is greater, i.e., the height of the first marker point is less than the height of the first region but greater than the height of the second region. At the same time, the thinning degree of the first marker point is controlled so that there is a height difference of 0~3μm between the first marker point and the first region surrounding the first marker point, which facilitates the grasping of the second laser processing in the subsequent step (5) and helps the formation of the second marker point. By controlling the laser single-pulse energy density of the second marker point to be less than that of the isolation region, and further controlling the alkaline concentration and time in the secondary wet etching, the thinning range of the isolation region is greater, so that the height of the second marker point is greater than the height of the isolation region. Finally, the height of the first marker point > the height of the second marker point > the height of the isolation region is obtained.
[0070] The present invention will be further described below with reference to specific embodiments.
[0071] Example 1
[0072] This embodiment provides a back contact battery, including:
[0073] A silicon substrate having a front and a back side that are positioned opposite to each other;
[0074] A front passivation layer is disposed on the front side of the silicon substrate;
[0075] A first region and a second region are alternately disposed on the back side of the silicon substrate; the first region sequentially includes a first tunneling oxide layer, a P-type doped polysilicon layer, a back passivation layer, and a metal positive electrode along the direction away from the silicon substrate, wherein the P-type doped polysilicon layer is in ohmic contact with the metal positive electrode; the second region sequentially includes a second tunneling oxide layer, an N-type doped polysilicon layer, a back passivation layer, and a metal negative electrode along the direction away from the silicon substrate, wherein the N-type doped polysilicon layer is in ohmic contact with the metal negative electrode;
[0076] An isolation region located between the first region and the second region, the isolation region being recessed inward and closer to the silicon substrate relative to the first region and the second region;
[0077] The back of the silicon substrate is provided with a first marker point and a second marker point that surrounds the first marker point, and the height difference between the first marker point and the second marker point is 2μm.
[0078] The area of the first marker point is 50% of the area of the second marker point.
[0079] The method for preparing the back contact battery in this embodiment includes the following steps:
[0080] (1) Polishing the silicon substrate;
[0081] (2) A first tunneling oxide layer and a first polysilicon layer are sequentially formed on the back side of the silicon substrate. The first polysilicon layer is doped to form a P-type doped polysilicon layer, and a first mask layer is formed on the surface of the P-type doped polysilicon layer.
[0082] (3) The second region and the first marker point are subjected to the first laser treatment to remove or thin the first mask layer, and then the first laser treatment area is thinned by a wet etching process. The first marker point and the second region have a height difference. In the first laser treatment, the laser spot size is 300 μm, and the laser single pulse energy density for the second region is 200 mJ / cm². 2 The laser single-pulse energy density at the first marker point is 150 mJ / cm². 2 In a single wet etching process, a 5% sodium hydroxide solution and a 0.5% protective additive are reacted at 85°C for 200 seconds.
[0083] (4) A second tunneling oxide layer and a second polysilicon layer are sequentially formed on the back side of the silicon substrate. The second polysilicon layer is doped to form an N-type doped polysilicon layer, and a second mask layer is formed on the surface of the N-type doped polysilicon layer.
[0084] (5) Perform a second laser treatment on the first region, the second marker point, and the isolation region to remove or thin the second mask layer, and then use a secondary wet etching process to thin the second laser treatment area. The first marker point and the second marker point have a height difference. In the second laser treatment, the laser spot size is 300 μm, and the laser single pulse energy density for the first region is 200 mJ / cm². 2 The laser single-pulse energy density at the second marker point is 300 mJ / cm². 2 The laser single-pulse energy density in the isolated area outside the second marker point is 350 mJ / cm². 2 In the secondary wet etching process, a 2.5% sodium hydroxide solution and a 0.5% protective additive are used to react at 75°C for 600 seconds.
[0085] (6) Remove the remaining first and second mask layers;
[0086] (7) Texturing the front side and isolation area of the silicon substrate to form a pyramid textured surface;
[0087] (8) Deposit passivation layers on the front and back sides of the silicon substrate to form a front passivation layer and a back passivation layer;
[0088] (9) A positive metal electrode is printed in the first region on the back side of the silicon substrate, and a negative metal electrode is printed in the second region. After sintering, the positive metal electrode forms an ohmic contact with the P-type doped polysilicon layer, and the negative metal electrode forms an ohmic contact with the N-type doped polysilicon layer.
[0089] Example 2
[0090] The back contact battery structure and preparation method in this embodiment are basically the same as those in Embodiment 1, except that the height difference between the first marking point and the second marking point is 3 μm.
[0091] The main difference in their preparation methods lies in step (5), which is as follows:
[0092] In the secondary wet etching process, sodium hydroxide with a concentration of 2.5% and ADD2 with a concentration of 0.5% are reacted at 75°C for 700 seconds.
[0093] Example 3
[0094] The back contact battery structure and preparation method in this embodiment are basically the same as those in Embodiment 1, except that the height difference between the first marking point and the second marking point is 0.5 μm.
[0095] The main difference in their preparation methods lies in step (5), which is as follows:
[0096] In the secondary wet etching process, a 3% sodium hydroxide solution and a 0.5% ADD2 solution are reacted at 75°C for 500 seconds.
[0097] Example 4
[0098] The back contact battery structure in this embodiment is basically the same as that in Embodiment 1, with the only difference being:
[0099] The first marker point encloses the second marker point.
[0100] Example 5
[0101] The only difference between the back contact battery structure of this embodiment and that of Embodiment 1 is that the first marking point is a polished surface, and the second marking point is a textured surface, as shown in Figures 2-3. Specifically:
[0102] This embodiment provides a back contact battery, including:
[0103] A silicon substrate having a front and a back side that are positioned opposite to each other;
[0104] A front passivation layer is disposed on the front side of the silicon substrate;
[0105] A first region and a second region are alternately disposed on the back side of the silicon substrate; the first region sequentially includes a first tunneling oxide layer, a P-type doped polysilicon layer, a back passivation layer, and a metal positive electrode along the direction away from the silicon substrate, wherein the P-type doped polysilicon layer is in ohmic contact with the metal positive electrode; the second region sequentially includes a second tunneling oxide layer, an N-type doped polysilicon layer, a back passivation layer, and a metal negative electrode along the direction away from the silicon substrate, wherein the N-type doped polysilicon layer is in ohmic contact with the metal negative electrode;
[0106] An isolation region located between the first region and the second region, the isolation region being recessed inward and closer to the silicon substrate relative to the first region and the second region;
[0107] The back of the silicon substrate is provided with a first marker and a second marker that surrounds the first marker. The first marker is a polished surface and the second marker is a textured surface. The height difference between the first marker and the second marker is 2 μm.
[0108] The reflectivity of the first marker point is 30-40%, and the reflectivity of the second marker point is less than 15%. The width of the second marker point is smaller than the width of the isolation area, and the area of the first marker point is 50% of the area of the second marker point.
[0109] The method for preparing the back contact battery in this embodiment includes the following steps:
[0110] (1) Polishing the silicon substrate;
[0111] (2) A first tunneling oxide layer and a first polysilicon layer are sequentially formed on the back side of the silicon substrate. The first polysilicon layer is doped to form a P-type doped polysilicon layer, and a first mask layer is formed on the surface of the P-type doped polysilicon layer.
[0112] (3) The second region and the first marker point are subjected to the first laser treatment to remove or thin the first mask layer, and then the first laser treatment area is thinned by a wet etching process. The first marker point and the second region have a height difference. In the first laser treatment, the laser spot size is 300 μm, and the laser single pulse energy density for the second region is 200 mJ / cm². 2 The laser single-pulse energy density at the first marker point is 150 mJ / cm². 2 In a single wet etching process, a 5% sodium hydroxide solution and a 0.5% protective additive are reacted at 85°C for 200 seconds.
[0113] (4) A second tunneling oxide layer and a second polysilicon layer are sequentially formed on the back side of the silicon substrate. The second polysilicon layer is doped to form an N-type doped polysilicon layer, and a second mask layer is formed on the surface of the N-type doped polysilicon layer.
[0114] (5) Perform a second laser treatment on the first region, the second marker point, and the isolation region to remove or thin the second mask layer, and then use a secondary wet etching process to thin the second laser treatment area. The first marker point and the second marker point have a height difference. In the second laser treatment, the laser spot size is 300 μm, and the laser single pulse energy density for the first region is 200 mJ / cm². 2 The laser single-pulse energy density at the second marker point is 300 mJ / cm². 2 The laser single-pulse energy density in the isolated area outside the second marker point is 350 mJ / cm². 2 In the secondary wet etching process, a 2.5% sodium hydroxide solution and a 0.5% protective additive are used to react at 75°C for 600 seconds.
[0115] (6) Remove the remaining first and second mask layers;
[0116] (7) The front side of the silicon substrate, the second marker point and the isolation area are texturized to form a pyramid textured surface, and the first marker point is a polished surface;
[0117] (8) Deposit passivation layers on the front and back sides of the silicon substrate to form a front passivation layer and a back passivation layer;
[0118] (9) A positive metal electrode is printed in the first region on the back side of the silicon substrate, and a negative metal electrode is printed in the second region. After sintering, the positive metal electrode forms an ohmic contact with the P-type doped polysilicon layer, and the negative metal electrode forms an ohmic contact with the N-type doped polysilicon layer.
[0119] Example 6
[0120] The back contact battery structure and preparation method in this embodiment are basically the same as those in Embodiment 5, except that the height difference between the first marking point and the second marking point is 1.5 μm.
[0121] The main difference in their preparation methods lies in step (5), which is as follows:
[0122] In the secondary wet etching process, 1% sodium hydroxide and 0.5% ADD2 are reacted at 75°C for 700 seconds.
[0123] Example 7
[0124] The back contact battery structure and preparation method in this embodiment are basically the same as those in Embodiment 5, except that the height difference between the first marking point and the second marking point is 2.5 μm.
[0125] The main difference in their preparation methods lies in step (5), which is as follows:
[0126] In the secondary wet etching process, a 5% sodium hydroxide solution and a 0.5% ADD2 solution are reacted at 75°C for 500 seconds.
[0127] Example 8
[0128] The back contact battery structure and preparation method in this embodiment are basically the same as those in Embodiment 5, except that the height difference between the first marking point and the second marking point is 2 μm.
[0129] The main difference in their preparation methods lies in step (5), which is as follows:
[0130] In the secondary wet etching process, sodium hydroxide with a concentration of 3.5% and ADD2 with a concentration of 0.5% are reacted at 75°C for 550 seconds.
[0131] Example 9
[0132] The back contact battery structure in this embodiment is basically the same as that in embodiment 5, except that the area of the first marking point is 20% of the area of the second marking point.
[0133] Example 10
[0134] The back contact battery structure in this embodiment is basically the same as that in embodiment 5, except that the area of the first marking point is 85% of the area of the second marking point.
[0135] Example 11
[0136] The back contact battery structure in this embodiment is basically the same as that in embodiment 5, except that the area of the first marking point is 5% of the area of the second marking point.
[0137] Example 12
[0138] The back contact battery structure in this embodiment is basically the same as that in embodiment 5, except that the area of the first marking point is 90% of the area of the second marking point.
[0139] Example 13
[0140] The back contact battery structure in this embodiment is basically the same as that in Embodiment 5, with the only difference being:
[0141] As shown in Figures 4-5, the back of the silicon substrate is provided with a second marker and a first marker that surrounds the second marker, and the area of the second marker is 50% of the area of the first marker.
[0142] Comparative Example 1
[0143] The back contact battery structure and preparation method of this comparative example are basically the same as those of Example 1, with the only difference being:
[0144] The height difference between the first marker point and the second marker point is 0.
[0145] The main difference in their preparation methods lies in step (5), which is as follows:
[0146] The reaction time in the secondary wet etching process is less than 500 seconds.
[0147] Comparative Example 2
[0148] The back contact battery structure and preparation method of this comparative example are basically the same as those of Example 1, with the only difference being:
[0149] The height difference between the first marker point and the second marker point is 4 μm.
[0150] The main difference in their preparation methods lies in step (5), which is as follows:
[0151] In the secondary wet etching process, sodium hydroxide with a concentration of 2.5% and ADD2 with a concentration of 0.5% are reacted at 75°C for 700 seconds.
[0152] Comparative Example 3
[0153] The back contact battery structure and preparation method of this comparative example are basically the same as those of Example 1, with the only difference being:
[0154] The height difference between the first marker point and the second marker point is 5 μm.
[0155] The main difference in their preparation methods lies in step (5), which is as follows:
[0156] In the secondary wet etching process, sodium hydroxide with a concentration of 2.5% and ADD2 with a concentration of 0.5% are reacted at 75°C for 800 seconds.
[0157] Comparative Example 4
[0158] The back contact battery structure and preparation method of this comparative example are basically the same as those of Comparative Example 1, with the only difference being that the first marking point is a polished surface and the second marking point is a textured surface.
[0159] The performance of the solar cells prepared in each embodiment and comparative example was tested, and the results are shown in Table 1.
[0160] Table 1
[0161]
[0162] As shown in Table 1, the test results of Examples 1-13 and Comparative Examples 1-4 demonstrate that this invention, by setting a first and a second marker with a height difference in the isolation area, facilitates effective and accurate identification, ensuring the printing accuracy of subsequent overprinting, thereby improving the yield rate of solar cell production and reducing production costs. The test results of Examples 1-3 and Comparative Examples 5-8 show that, under the premise of satisfying the height difference, further processing the two markers into textured and polished surfaces respectively, creating a significant morphological difference, further facilitates alignment and improves printing yield. The test results of Examples 5 and 9-12 show that when the first and second markers satisfy the corresponding height difference and morphological difference, a better differentiation effect is achieved when the area of the first marker is 20-85% of the area of the second marker, further contributing to improved printing accuracy. The test results of Examples 1, 4, 5, and 13 show that whether the first marker wraps around the second marker or vice versa, accurate printing can be achieved under the corresponding morphological or height difference requirements. As can be seen from the test results of Example 1 and Comparative Examples 1-4, when the height difference is too small, it is impossible to perform the gripping, resulting in process abnormalities; when the height difference is too large, it will degrade the battery performance; if there is only a difference in shape and no height difference, the alignment printing accuracy will be worse, which will reduce the product yield.
[0163] The present invention has been further described above with reference to specific embodiments. However, it should be understood that the specific description herein should not be construed as limiting the substance and scope of the present invention. Various modifications made by those skilled in the art to the above embodiments after reading this specification are all within the scope of protection of the present invention.
Claims
1. A back-contact battery, characterized in that, include: A silicon substrate having a front and a back side that are positioned opposite to each other; A front passivation layer is disposed on the front side of the silicon substrate; A first region and a second region are alternately disposed on the back side of the silicon substrate; the first region sequentially includes a first tunneling oxide layer, a first doped polysilicon layer, a back passivation layer, and a first metal electrode along the direction away from the silicon substrate, with the first doped polysilicon layer in ohmic contact with the first metal electrode; the second region sequentially includes a second tunneling oxide layer, a second doped polysilicon layer, a back passivation layer, and a second metal electrode along the direction away from the silicon substrate, with the second doped polysilicon layer in ohmic contact with the second metal electrode; an isolation region is located between the first region and the second region, the isolation region being recessed inward and closer to the silicon substrate than the first region and the second region; The back side of the silicon substrate is provided with a first marker point and a second marker point for alignment printing. The second marker point wraps around the first marker point or the first marker point wraps around the second marker point. The height difference D between the first marker point and the second marker point satisfies 0 < D ≤ 3, and the unit is μm.
2. The back contact battery according to claim 1, characterized in that, The height difference between the first marker point and the second marker point is 0.5μm~2.5μm.
3. The back contact battery according to claim 1, characterized in that, The first marking point is a polished surface, and the second marking point is a velvety surface.
4. The back contact battery according to claim 3, characterized in that, The reflectivity of the first marker point is 30%~40%, and the reflectivity of the second marker point is less than 15%.
5. The back contact battery according to claim 1, characterized in that, When the second marker point encloses the first marker point, the area of the first marker point is 20% to 85% of the area of the second marker point.
6. The back contact battery according to claim 1, characterized in that, When the first marker point encloses the second marker point, the area of the second marker point is 20% to 85% of the area of the first marker point.