TOPCon solar cell and preparation method thereof

Abstract

The invention relates to a TOPCon solar cell and a preparation method thereof, the cell comprises a silicon substrate, and the back surface of the silicon substrate is provided with metallized regions and non-metallized regions which are alternately arranged; a tunneling oxide layer, a doped polycrystalline silicon layer, a back passivation layer and a back metal electrode are sequentially arranged in the metalized region from inside to outside, and the back metal electrode is in ohmic contact with the doped polycrystalline silicon layer; the non-metallization area is recessed inwards and is closer to the silicon substrate than the metallization area; the non-metallization area comprises a mark point area and a non-mark point area; the height difference between the mark point area and the non-mark point area is 0.1 [mu] m-10 [mu] m. The obvious height difference is formed between the mark point area and the non-mark point area, the mark points can be accurately and effectively recognized, guarantee is provided for the printing precision of follow-up overprinting, the yield of solar cell production can be increased, and the production cost is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of solar cells, and in particular to a TOPCon solar cell and a preparation method thereof. Background Art

[0002] In the solar cell industry, as the number of electrodes on cell panels increases, along with increasingly complex structures and technologies, precise overprinting is essential during electrode printing. The emergence of new cell structures, such as TOPCon and xBC, places even higher demands on precision during production. Laser marking technology can accurately create markings on complex cell surfaces, providing a reliable reference for subsequent processing and testing, meeting the production requirements of these new cell structures.

[0003] Laser marking points can improve production efficiency and accuracy. Specifically, laser marking points can provide accurate 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 marking points can help the equipment quickly and accurately find the welding position and packaging position, reducing errors and rework.

[0004] Currently, in the TOPCon battery field, laser marking is used on the front velvet surface. This surface is then flattened or flattened to create a contrast difference in appearance, enabling the marking point to be captured. This is a conventional two-dimensional (2D) recognition and capture method. However, in the TOPCon Poly Finger structure, the marking points are all on the polished back surface. Conventional lasers cannot create a contrast difference between the marking point area and the normal area, resulting in low recognition accuracy during the printing and overprinting process, affecting product yield. Therefore, in order to achieve high-precision recognition for subsequent products, a three-dimensional (3D) marking point recognition technology is needed. Summary of the Invention

[0005] In order to solve the above technical problems, the present invention provides a solar cell and a method for preparing the same, which forms a significant height difference between the marking point area and the non-marking point area, thereby accurately and effectively identifying the marking points and improving printing accuracy.

[0006] The present invention adopts the following technical solutions:

[0007] A TOPCon solar cell includes a silicon substrate,

[0008] The front surface of the silicon substrate has an emitter, a front passivation layer, and a front metal electrode in order from the inside to the outside, and the front metal electrode is in ohmic contact with the emitter;

[0009] The back side of the silicon substrate has metallized areas and non-metallized areas arranged alternately;

[0010] The metallized region comprises, from the inside to the outside, a tunneling oxide layer, a doped polysilicon layer, a back passivation layer, and a back metal electrode, wherein the back metal electrode is in ohmic contact with the doped polysilicon layer;

[0011] The non-metallized region is recessed inwardly and is closer to the silicon substrate than the metallized region;

[0012] The non-metallized area includes a marking point area and a non-marking point area for realizing registration printing;

[0013] The mark point area and the non-mark point area have a height difference of 0.1 μm to 10 μm.

[0014] Furthermore, the height difference between the marking point area and the non-marking point area is 2 μm to 6 μm.

[0015] Furthermore, the reflectivity difference between the marking point area and the non-marking point area is 0.5% to 30%.

[0016] Furthermore, the shape of the marking point area is any one of a cross, a circle, a triangle, a quadrilateral, and a hexagon.

[0017] Furthermore, the width of the marking point area is 0.1 mm to 1.5 mm.

[0018] The present invention also provides a method for preparing the above-mentioned TOPCon battery, comprising the following steps:

[0019] (1) The silicon substrate is textured on both sides, and boron is diffused on the front side to form an emitter;

[0020] (2) The BSG layer is removed from the back of the silicon substrate and polished, and a tunneling oxide layer, a doped polysilicon layer, and a mask layer are formed on the back in sequence;

[0021] (3) Remove part / all of the mask layer from the non-metallized area;

[0022] (4) performing laser processing and etching cleaning on the non-metallized area, and thinning the marking point area and / or the non-marking point area, wherein the marking point area and the non-marking point area have a height difference;

[0023] (5) Removing the residual mask layer;

[0024] (6) Forming a front passivation layer and a back passivation layer, printing a back metal electrode on the back metallization area, and printing a front metal electrode on the front.

[0025] Furthermore, the tunneling oxide layer and the doped polysilicon layer region are removed from the non-metallized region to form a non-marking point region, and the tunneling oxide layer and the doped polysilicon layer region are not removed from the non-metallized region to form a marking point region, and the marking point region is higher than the non-marking point region; or

[0026] The tunneling oxide layer and the doped polysilicon layer area are removed from the non-metallized area to form a non-marking point area, and the tunneling oxide layer, the doped polysilicon layer and part of the silicon substrate area are removed from the non-metallized area to form a marking point area, and the marking point area is lower than the non-marking point area.

[0027] Furthermore, in step (4), the laser spot size is 100 μm to 550 μm, and the laser single pulse energy density is 80 mJ / cm 2 ~500mJ / cm 2 .

[0028] Furthermore, when the marking point area is lower than the non-marking point area, the laser single pulse energy density in the marking point area is greater than the laser single pulse energy density in the non-marking point area.

[0029] Furthermore, the corrosion cleaning is carried out by using an acid solution with a concentration of 5% to 45% for 10s to 320s; or,

[0030] Use alkali solution with a concentration of 0.1%~1.5% and react for 30s~350s.

[0031] The present invention has the following beneficial effects:

[0032] The solar cell of the present invention is provided with a non-metallized area that is recessed inward, and forms a marking point area and a non-marking point area with a height difference in the non-metallized area, which helps to accurately and effectively identify the marking points during the printing process, realize precise registration printing, provide a guarantee for the printing accuracy of subsequent overprinting, improve the yield rate of solar cell production, and reduce production costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the embodiments of the present application or the technical solutions of the prior art, the following is a brief introduction to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0034] Figure 1 This is a schematic cross-sectional view of the TOPCon solar cell structure of this application;

[0035] Figure 2 This is a front view of the TOPCon solar cell structure of this application;

[0036] Figure 3 for Figure 2 Enlarged view of the middle area;

[0037] Description of the drawings: 1-silicon substrate, 2-emitter, 3-front passivation layer, 4-front metal electrode, 5-metallized area, 6-non-metallized area, 7-tunneling oxide layer, 8-doped polysilicon layer, 9-back passivation layer, 10-back metal electrode, 11-marking point area, 12-non-marking point area. DETAILED DESCRIPTION

[0038] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0039] The marking point referred to in the present invention, which may also be called an identification point or a Mark point, refers to a closed area with certain characteristics within a certain range. It is a uniquely identifiable point or shape in the nearby area (or within the field of view of the recognition camera).

[0040] In a first aspect, the present invention provides a TOPCon solar cell, such as Figure 1-3 As shown, it includes a silicon substrate 1,

[0041] The front surface of the silicon substrate 1 has an emitter 2, a front passivation layer 3, and a front metal electrode 4 in order from the inside to the outside. The front metal electrode 4 is in ohmic contact with the emitter 2.

[0042] The back side of the silicon substrate 1 has metallized areas 5 and non-metallized areas 6 arranged alternately;

[0043] The metallized region 5 has, from the inside to the outside, a tunneling oxide layer 7, a doped polysilicon layer 8, a back passivation layer 9, and a back metal electrode 10, wherein the back metal electrode 10 is in ohmic contact with the doped polysilicon layer 8;

[0044] The non-metallized region 6 is recessed inwards and is closer to the silicon substrate 1 than the metallized region 5 ;

[0045] The non-metallized area 6 includes a marking point area 11 for realizing registration printing and a non-marking point area 12;

[0046] The height difference between the marking point area and the non-marking point area is 0.1 μm to 10 μm.

[0047] The TOPCon solar cell of the present invention utilizes a height difference between marking and non-marking areas within a non-metallized region. This facilitates accurate and effective identification of marking points, ensuring the accuracy of subsequent overprinting, improving the yield rate of solar cell production, and reducing production costs. Furthermore, this height difference ensures significant contrast differences between marking points in 3D, making them easier to grasp and achieving better printing accuracy than marking points placed only on a flat surface.

[0048] Specifically, as some embodiments of the present invention, the marking point area 11 has a tunneling oxide layer 7, a doped polysilicon layer 8, and a back passivation layer 9 from the inside to the outside, the non-marking point area 12 includes the back passivation layer 9, and the marking point area 11 is higher than the non-marking point area 12; or,

[0049] The marking area 11 and the non-marking area 12 include a back passivation layer 9 . A portion of the silicon substrate is removed from the marking area 11 . The marking area 11 is lower than the non-marking area 12 .

[0050] Part of the non-metallized area is thinned, and the marking point area is located in the non-metallized area that has not been thinned, including the tunneling oxide layer, the doped polysilicon layer, and the back passivation layer, while the tunneling oxide layer and the doped polysilicon layer are thinned in the non-marking point area, and only the back passivation layer is included, so that the marking point area is higher than the non-marking point area; or both the marking point area and the non-marking point area are located in the non-metallized area and partially thinned (i.e., the tunneling oxide layer and the doped polysilicon layer are removed), but the marking point area is thinned to a greater extent, and the marking point area thins part of the silicon substrate, and the silicon substrate thickness of the marking point area is less than that of the non-marking point area, so that the marking point area is lower than the non-marking point area; the above two methods are used to achieve a significant height difference between the marking point area and the non-marking point area. Figure 2-3 As shown, the non-marking point area is located in the non-metallized area and near the marking point area; by setting the marking point area at the four corners of the battery, a height difference is formed between the non-marking point area and the marking point area, indicating an obvious contrast difference, so that accurate alignment can be achieved during alignment printing. The marking points of the present invention can realize accurate alignment printing of electrodes in the front-end process of battery preparation, which helps to improve the yield rate of the battery. At the same time, unlike the marking points formed for tracking the finished battery cells in the prior art, in the finished battery prepared by the present invention, the marking point area can be completely covered after the precise alignment printing is completed, and will not affect the appearance and application of the subsequent finished battery product.

[0051] More specifically, as some embodiments of the present invention, the height difference between the mark point area and the non-mark point area is 0.1μm, 0.2μm, 0.3μm, 0.4μm, 0.5μm, 0.6μm, 0.7μm, 0.8μm, 0.9μm, 1μm, 1.5μm, 2μm, 2.5μm, 3μm, 3.5μm, 4μm, 4.5μm, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm or any range between the two; preferably, the height difference between the mark point area and the non-mark point area is 2μm~6μm. If the height difference is too small, the recognition difficulty is greater and the accuracy is lower; if the height difference is too large, the subsequent process difficulty and production cost are increased. In the present invention, the height difference between the mark point area and the non-mark point area is obtained by testing with an Olympus semiconductor microscope or other microscopic morphology instruments.

[0052] Specifically, in some embodiments of the present invention, the difference in reflectivity between the marked area and the non-marked area is 0.5% to 30%. Preferably, the difference in reflectivity between the marked area and the non-marked area is 10% to 30%.

[0053] Specifically, as some embodiments of the present invention, the shape of the marking point area is a circle, a cross, a triangle, a quadrilateral, a pentagon, a hexagon or other closed shapes.

[0054] Specifically, in some embodiments of the present invention, the width of the marking area is 0.1mm to 1.5mm. Non-metallized areas and metallized areas are interlaced. The width of the marking area in the present invention is the distance between the marking area and two adjacent metallized areas in the perpendicular direction. If the width is too small, the marking effect is limited; if the width is too large, the marking area will be too close to the metallized areas on either side, affecting the structure of the metallized areas.

[0055] The present invention also provides a method for preparing the above-mentioned TOPCon solar cell, comprising the following steps:

[0056] (1) The silicon substrate is textured on both sides, and boron is diffused on the front side to form an emitter;

[0057] (2) The BSG layer is removed from the back of the silicon substrate and polished, and a tunneling oxide layer, a doped polysilicon layer, and a mask layer are formed on the back in sequence;

[0058] (3) Remove part / all of the mask layer from the non-metallized area;

[0059] (4) performing laser processing and etching cleaning on the non-metallized area, and thinning the marking point area and / or the non-marking point area, wherein the marking point area and the non-marking point area have a height difference;

[0060] (5) Removing the residual mask layer;

[0061] (6) Forming a front passivation layer and a back passivation layer, printing a back metal electrode on the back metallization area, and printing a front metal electrode on the front.

[0062] Specifically, as some embodiments of the present invention, the tunneling oxide layer and the doped polysilicon layer region are removed from the non-metallized region to form a non-marking point region, and the tunneling oxide layer and the doped polysilicon layer region are not removed from the non-metallized region to form a marking point region, and the marking point region is higher than the non-marking point region; or,

[0063] The tunneling oxide layer and the doped polysilicon layer region are removed from the non-metallized region to form a non-marking point region, and the tunneling oxide layer, the doped polysilicon layer and a portion of the silicon substrate region are removed from the non-metallized region to form a marking point region, wherein the marking point region is lower than the non-marking point region;

[0064] The height difference between the marking point area and the non-marking point area is 0.1 μm to 10 μm.

[0065] The method for preparing a solar cell of the present invention controls the marking point area not to be thinned or to be thinned to a greater extent during the process of thinning and removing the non-metallized area. Specifically, a portion of the mask layer of the non-metallized area is removed, and the portion of the non-metallized area is thinned. The marking point area is located in the non-metallized area that has not been thinned, including a tunneling oxide layer and a doped polysilicon layer, while the tunneling oxide layer and the doped polysilicon layer are thinned in the non-marking point area, so that the marking point area is higher than the non-marking point area; or all the mask layers of the non-metallized area are removed, and the marking point area and the non-marking point area are both located in the non-metallized area and thinned, but the marking point area is thinned to a greater extent, so that the marking point area is lower than the non-marking point area.

[0066] Specifically, as some embodiments of the present invention, the laser spot size is 100μm~550μm; more specifically, the laser spot size is 100μm, 120μm, 150μm, 180μm, 200μm, 220μm, 250μm, 280μm, 300μm, 320μm, 350μm, 380μm, 400μm, 420μm, 450μm, 480μm, 500μm, 520μm, 550μm or any range of two values. The single pulse energy density of the laser is 80mJ / cm 2 ~500mJ / cm 2 More specifically, the laser's single pulse energy density is 80 mJ / cm 2 、100mJ / cm 2 、120mJ / cm 2 、150mJ / cm 2 、180mJ / cm2 , 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 any range of values consisting of both.

[0067] When the marking point area is lower than the non-marking point area, the laser single pulse energy density in the marking point area is greater than the laser single pulse energy density in the non-marking point area.

[0068] Specifically, in some embodiments of the present invention, the etching cleaning is performed using an acid solution with a concentration of 5% to 45% for a reaction time of 10 to 320 seconds. More specifically, HF is used for the reaction; the acid solution concentration is 5%, 8%, 10%, 12%, 15%, 18%, 20%, 22%, 25%, 27%, 30%, 32%, 35%, 38%, 40%, 42%, 45%, or any range therebetween; and the reaction time is 10 seconds, 20 seconds, 50 seconds, 60 seconds, 80 seconds, 100 seconds, 120 seconds, 150 seconds, 180 seconds, 200 seconds, 240 seconds, 270 seconds, 300 seconds, 320 seconds, or any range therebetween.

[0069] Specifically, in some embodiments of the present invention, the corrosion cleaning is performed using an alkaline solution with a concentration of 0.1% to 1.5% for a reaction time of 30 to 350 seconds. More specifically, NaOH or KOH is used for the reaction; the alkaline solution concentration is 0.1%, 0.2%, 0.5%, 0.8%, 1.0%, 1.2%, 1.4%, 1.5%, or any range therebetween; and the reaction time is 30 seconds, 40 seconds, 50 seconds, 60 seconds, 80 seconds, 100 seconds, 120 seconds, 150 seconds, 180 seconds, 200 seconds, 240 seconds, 270 seconds, 300 seconds, 320 seconds, 350 seconds, or any range therebetween.

[0070] The present invention will be further described below with reference to specific embodiments.

[0071] Example 1

[0072] This embodiment provides a TOPCon solar cell, comprising a silicon substrate,

[0073] The front surface of the silicon substrate has an emitter, a front passivation layer, and a front metal electrode in order from the inside to the outside, and the front metal electrode is in ohmic contact with the emitter;

[0074] The back side of the silicon substrate has metallized areas and non-metallized areas arranged alternately;

[0075] The metallized region comprises, from the inside to the outside, a tunneling oxide layer, a doped polysilicon layer, a back passivation layer, and a back metal electrode, wherein the back metal electrode is in ohmic contact with the doped polysilicon layer;

[0076] The non-metallized region is recessed inwardly and is closer to the silicon substrate than the metallized region;

[0077] The non-metallized area includes a marking point area and a non-marking point area;

[0078] The height difference between the marking point area and the non-marking point area is 4 μm, the width of the marking point area is 0.8 mm, and the reflectivity difference between the marking point area and the non-marking point area is 15%.

[0079] The method for preparing the TOPCon solar cell of this embodiment includes the following steps:

[0080] (1) The silicon substrate is textured and boron is diffused on the front of the silicon substrate to form an emitter;

[0081] (2) Remove the boron-doped layer on the back side and polish it, deposit a tunnel oxide layer and a polysilicon layer on the back side of the silicon substrate in sequence, and dope the polysilicon layer with phosphorus to form a doped polysilicon layer, using the PSG layer as a mask layer;

[0082] (3) Removing part of the mask layer in the non-metallized area;

[0083] (4) Laser treatment and sodium hydroxide etching cleaning are performed on the non-metallized area, and the non-marking area is thinned. The tunneling oxide layer and the doped polysilicon layer of the mask layer in the non-metallized area are removed. During the laser cleaning, the laser spot size is 300μm, and the single pulse energy density of the laser is 250mJ / cm 2 ; In the corrosion cleaning, a 1% sodium hydroxide solution was used for 200 seconds;

[0084] (5) Removing the mask layer;

[0085] (6) forming a front passivation layer and a back passivation layer on the front and back sides of the silicon substrate, respectively, printing a front metal electrode on the front passivation layer, and printing a back metal electrode on the back metallized area; the front metal electrode forms an ohmic contact with the emitter, and the back metal electrode forms an ohmic contact with the doped polysilicon layer.

[0086] Example 2

[0087] The only difference between this embodiment and the TOPCon solar cell in embodiment 1 is that:

[0088] The height difference between the marking point area and the non-marking point area is 0.1 μm, and the reflectivity difference between the marking point area and the non-marking point area is 0.5%.

[0089] The preparation method of the TOPCon solar cell of this embodiment is basically the same as that of Example 1, with the only difference being step (4), which is specifically:

[0090] (4) The silicon substrate is laser treated and cleaned with sodium hydroxide corrosion, the non-marking area is thinned, and the tunneling oxide layer and the doped polysilicon layer of the mask layer in the non-metallized area are removed; during laser cleaning, the laser spot size is 100 μm, and the single pulse energy density of the laser is 80 mJ / cm 2 ; During corrosion cleaning, 0.1% sodium hydroxide was used for reaction for 350 seconds.

[0091] Example 3

[0092] The only difference between this embodiment and the TOPCon solar cell in embodiment 1 is that:

[0093] There is a height difference of 10 μm between the marking point area and the non-marking point area, and a reflectivity difference of 30% between the marking point area and the non-marking point area.

[0094] The preparation method of the TOPCon solar cell of this embodiment is basically the same as that of Example 1, with the only difference being step (4), which is specifically:

[0095] (4) The silicon substrate is laser treated and cleaned with sodium hydroxide corrosion, the non-marking area is thinned, and the tunneling oxide layer and the doped polysilicon layer of the mask layer in the non-metallized area are removed; during laser cleaning, the laser spot size is 550μm, and the single pulse energy density of the laser is 500mJ / cm 2 ; During corrosion cleaning, use 1.5% sodium hydroxide for 30 seconds.

[0096] Example 4

[0097] The only difference between this embodiment and the TOPCon solar cell in embodiment 1 is that:

[0098] There is a height difference of 2 μm between the marking point area and the non-marking point area, and a reflectivity difference of 10% between the marking point area and the non-marking point area.

[0099] The preparation method of the TOPCon solar cell of this embodiment is basically the same as that of Example 1, with the only difference being step (4), which is specifically:

[0100] (4) The silicon substrate is laser treated and cleaned with sodium hydroxide corrosion, the non-marking area is thinned, and the tunneling oxide layer and the doped polysilicon layer of the mask layer in the non-metallized area are removed; during laser cleaning, the laser spot size is 200μm, and the single pulse energy density of the laser is 150mJ / cm 2 ; In corrosion cleaning, use 1% sodium hydroxide for 200 seconds.

[0101] Example 5

[0102] The only difference between this embodiment and the TOPCon solar cell in embodiment 1 is that:

[0103] The height difference between the marking point area and the non-marking point area is 6 μm, and the reflectivity difference between the marking point area and the non-marking point area is 22%.

[0104] The preparation method of the TOPCon solar cell of this embodiment is basically the same as that of Example 1, with the only difference being step (4), which is specifically:

[0105] (4) The silicon substrate is laser treated and cleaned with sodium hydroxide corrosion, the non-marking area is thinned, and the tunneling oxide layer and the doped polysilicon layer of the mask layer in the non-metallized area are removed; during laser cleaning, the laser spot size is 450μm, and the single pulse energy density of the laser is 400mJ / cm 2 ; In corrosion cleaning, use 1% sodium hydroxide for 200 seconds.

[0106] Example 6

[0107] This embodiment is basically the same as Embodiment 1, with the only difference being that the width of the marking point area is 0.1 mm.

[0108] Example 7

[0109] This embodiment is basically the same as Embodiment 1, with the only difference being that the width of the marking point area is 1.5 mm.

[0110] Example 8

[0111] This embodiment is basically the same as Embodiment 1, with the only difference being that the width of the marking point area is 0.07 mm.

[0112] Example 9

[0113] This embodiment is basically the same as Embodiment 1, with the only difference being that the width of the marking point area is 1.6 mm.

[0114] Example 10

[0115] This embodiment is basically the same as the embodiment 1, with the only difference being that the marking point area is lower than the non-marking point area, with a height difference of 4 μm.

[0116] The preparation method of the TOPCon solar cell of this embodiment is basically the same as that of Example 1, with the only difference being steps (3) to (4), specifically:

[0117] (3) Remove all mask layers in non-metallized areas;

[0118] (4) The non-metallized area is thinned by laser treatment and sodium hydroxide corrosion cleaning. During laser cleaning, the laser spot size is 300μm, and the single pulse energy density of the laser in the non-marking area is 250mJ / cm 2 The single pulse energy density of the laser in the marking area is 400mJ / cm 2 .

[0119] Comparative Example 1

[0120] This comparative example provides a TOPCon solar cell structure, which differs from Example 1 in that:

[0121] The height difference between the marking point area and the non-marking point area is 0.07 μm.

[0122] Comparative Example 2

[0123] This comparative example provides a TOPCon solar cell structure, which differs from Example 1 in that:

[0124] The height difference between the marking point area and the non-marking point area is 11 μm.

[0125] The solar cells prepared in the examples and comparative examples were subjected to performance tests, and the results are shown in Table 1.

[0126] Table 1

[0127] Group Eta (%) Uoc (mV) Isc (A) FF (%) Yield (%) Example 1 26.65 733.13 14.05 86.28 99.50 Example 2 26.39 729.04 14.02 86.12 97.88 Example 3 26.53 731.13 14.03 86.26 98.30 Example 4 26.58 732.18 14.03 86.25 98.70 Example 5 26.54 731.13 14.04 86.20 98.38 Example 6 26.46 729.89 14.02 86.23 98.11 Example 7 26.51 731.23 14.02 86.22 98.27 Example 8 26.39 729.01 14.01 86.13 97.89 Example 9 26.44 729.50 14.02 86.19 98.33 Example 10 26.53 731.15 14.03 86.22 98.37 Comparative Example 1 26.07 728.85 13.97 85.37 92.53 Comparative Example 2 25.88 727.37 13.89 85.37 89.15

[0128] As can be seen from the test results of Examples 1-10 and Comparative Examples 1-2 in Table 1, the present invention forms a significant height difference between the marking point area and the non-marking point area, which helps to effectively identify the marking point, achieve accurate alignment printing, and provide protection for the printing accuracy of subsequent overprinting. The yield rate of the obtained solar cell is greater than 97.5%. As can be seen from the test results of Examples 1 and 6-9, when the marking point area and the non-marking point area meet the corresponding height difference, when the width of the further marking point area is within the range of 0.1mm~1.5mm, the recognition effect of the marking point is better, which is more conducive to improving the printing accuracy. As can be seen from the test results of Examples 1 and 10, when the marking point area and the non-marking point area meet the height difference, no matter whether the marking point area is higher or lower than the non-marking point area, a good recognition effect can be achieved. As can be seen from the test results of Examples 1-10 and Comparative Examples 1-2, when the height difference is too small, it will affect the accuracy of the electrode printing process, thereby affecting the battery performance; when the height difference is too large, it will have too much impact on the silicon substrate, which will also degrade the battery performance.

[0129] The present invention is further described above with the aid of specific embodiments. However, it should be understood that the specific description herein should not be construed as limiting the essence and scope of the present invention. Various modifications made to the above embodiments by ordinary technicians in this field after reading this specification are all within the scope of protection of the present invention.

Claims

1. A TOPCon solar cell, characterized in that: including a silicon substrate, The front surface of the silicon substrate has an emitter, a front passivation layer, and a front metal electrode in order from the inside to the outside, and the front metal electrode is in ohmic contact with the emitter; The back side of the silicon substrate has metallized areas and non-metallized areas arranged alternately; The metallized region comprises, from the inside to the outside, a tunneling oxide layer, a doped polysilicon layer, a back passivation layer, and a back metal electrode, wherein the back metal electrode is in ohmic contact with the doped polysilicon layer; The non-metallized region is recessed inwardly and is closer to the silicon substrate than the metallized region; The non-metallized area includes a marking point area and a non-marking point area for realizing registration printing; The mark point area and the non-mark point area have a height difference of 0.1 μm to 10 μm.

2. The TOPCon solar cell according to claim 1, characterized in that The height difference between the marking point area and the non-marking point area is 2 μm to 6 μm.

3. The TOPCon solar cell according to claim 1, characterized in that The reflectivity difference between the marking point area and the non-marking point area is 0.5%~30%.

4. The TOPCon solar cell according to claim 1, characterized in that The shape of the marking point area is any one of a cross, a circle, a triangle, a quadrilateral, and a hexagon.

5. The TOPCon solar cell according to claim 1, characterized in that The width of the marking point area is 0.1mm~1.5mm.

6. The method for preparing a TOPCon solar cell according to any one of claims 1 to 5, characterized in that: The following steps are involved: (1) The silicon substrate is textured on both sides, and boron is diffused on the front side to form an emitter; (2) The BSG layer is removed from the back of the silicon substrate and polished, and a tunneling oxide layer, a doped polysilicon layer, and a mask layer are formed on the back in sequence; (3) Remove part / all of the mask layer from the non-metallized area; (4) performing laser processing and etching cleaning on the non-metallized area, and thinning the marking point area and / or the non-marking point area, wherein the marking point area and the non-marking point area have a height difference; (5) Removing the residual mask layer; (6) Forming a front passivation layer and a back passivation layer, printing a back metal electrode on the back metallization area, and printing a front metal electrode on the front.

7. The method for preparing a TOPCon solar cell according to claim 6, characterized in that: The tunnel oxide layer and the doped polysilicon layer are removed from the non-metallized area to form a non-marking point area, and the tunnel oxide layer and the doped polysilicon layer are not removed from the non-metallized area to form a marking point area, and the marking point area is higher than the non-marking point area; or, The tunneling oxide layer and the doped polysilicon layer area are removed from the non-metallized area to form a non-marking point area, and the tunneling oxide layer, the doped polysilicon layer and part of the silicon substrate area are removed from the non-metallized area to form a marking point area, and the marking point area is lower than the non-marking point area.

8. The method for preparing a TOPCon solar cell according to claim 6, wherein: In step (4), the laser spot size is 100 μm~550 μm, and the laser single pulse energy density is 80 mJ / cm 2 ~500mJ / cm 2 .

9. The method for preparing a TOPCon solar cell according to claim 6, wherein: When the marking point area is lower than the non-marking point area, the laser single pulse energy density in the marking point area is greater than the laser single pulse energy density in the non-marking point area.

10. The method for preparing a TOPCon solar cell according to claim 6, wherein: The corrosion cleaning is carried out by using an acid solution with a concentration of 5% to 45% for 10s to 320s; or Use alkali solution with a concentration of 0.1%~1.5% and react for 30s~350s.

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