Back-contact solar cell and fabrication method therefor, and cell module

Abstract

The present disclosure relates to the technical field of solar cells, and in particular to a back-contact solar cell and a fabrication method therefor, and a cell module. By using a mixed metal electrode structure, the portions of fine grid electrodes in overlapping regions between busbar electrodes and the fine grid electrodes are removed, and using a metal composite layer below the fine grid electrodes to replace conventional fine grid electrodes eliminates a spatial cross-over structure between the fine grid electrodes and the busbar electrodes, thereby reducing short-circuit defects caused by insufficient effective insulation thickness, and thus improving the yield of cells. Additionally, by defining the discontinuous length of the fine grid electrodes and the width of the busbar electrodes, a more generous tolerance range is provided for solder ribbon welding, and by defining the ratio of the thickness of the composite conductive layer to the width thereof in a first direction, the linear resistivity of the composite conductive layer is ensured, thereby avoiding additional power loss caused by excessively high resistivity. Replacing the fine grid electrodes with a planar composite conductive layer significantly reduces the thickness of the insulating layer, thereby lowering the material cost of the insulating layer.

Description

Back-contact solar cells and their fabrication methods, cell module methods

[0001] Cross-reference to related applications

[0002] This application claims priority to Chinese Patent Application No. 2024118661252, filed on December 18, 2024, entitled “Back Contact Solar Cell and Preparation Method Thereof, Battery Module”, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This disclosure belongs to the field of solar cell technology, specifically relating to a back-contact solar cell, its preparation method, and a cell module. Background Technology

[0004] Currently, in back-contact heterojunction solar cells, both the N-electrode and P-electrode are located on the back of the cell. Their electrode patterns often employ an alternating interdigitated pattern (e.g., the main grid is located at the end of the fine grid, eliminating the need for insulating adhesive to insulate both the main grid and fine grid electrodes), or a perpendicular distribution of the main grid and fine grid electrodes (the main grid is located in the middle of the fine grid, requiring insulating adhesive to insulate both). The perpendicular distribution of the main grid and fine grid electrodes allows for flexible arrangement of the number and position of the main grid electrodes, minimizes current transmission distance on the fine grid electrodes, and virtually eliminates current loss in the uncovered areas at the ends of the fine grid electrodes, thus achieving the highest efficiency.

[0005] However, this method of connecting the back contact battery has the following disadvantages: the fine grid electrode and the main grid electrode are completely insulated by insulating glue. In actual production, due to the difference between the height of the fine grid electrode and the height of the insulating glue layer, the effective insulation thickness (effective insulation thickness = insulating glue thickness - fine grid electrode thickness) will be insufficient, which will easily cause short circuits. In addition, if the thickness of the insulating glue is increased to ensure the effective insulation thickness, the consumption of insulating ink material will increase.

[0006] It should be noted that this part of the disclosure only provides background technology related to this disclosure, and does not necessarily constitute prior art or publicly known technology. Summary of the Invention

[0007] The purpose of this disclosure is to overcome the technical problem of insufficient effective insulation thickness between the fine grid electrode and the main grid electrode in existing back-contact solar cells.

[0008] To achieve the above objectives, in a first aspect, embodiments of this disclosure provide a back-contact solar cell, comprising:

[0009] Solar cell substrate;

[0010] A transparent conductive layer is disposed on the back side of the battery cell substrate;

[0011] A composite conductive layer is disposed on the side of the transparent conductive film layer away from the battery cell substrate;

[0012] A fine grid electrode is disposed on the side of the composite conductive layer away from the cell substrate;

[0013] The main gate electrode and the fine gate electrode overlap perpendicularly to each other, and the fine gate electrode is intermittently arranged in the area of ​​the perpendicular overlap. The intermittent length of the fine gate electrode is 0.1 to 10 mm. The insulating layer at least fills the intermittent area of ​​the fine gate electrode to isolate the composite conductive layer from the main gate electrode.

[0014] The ratio between the thickness of the composite conductive layer and the width of the composite conductive layer along the first direction satisfies the formula ρ. l =ρ0 / (b*h), where ρ l Let ρ0 be the linear resistivity of the composite conductive layer along the second direction, ρb be the bulk resistivity of the composite conductive layer, b be the width of the composite conductive layer along the first direction, and h be the thickness of the composite conductive layer. The linear resistivity ρ0 is the linear resistivity of the composite conductive layer. l The range is 0.5 to 3.5 Ω / cm; wherein, the first direction is the length extension direction of the main gate electrode, and the second direction is the length extension direction of the fine gate electrode;

[0015] The composite conductive layer has a thickness of 70nm to 550nm; the composite conductive layer includes: a first conductive layer and / or a second conductive layer stacked together, the first conductive layer having a thickness of 50nm to 450nm, and the second conductive layer having a thickness of 20nm to 100nm; the first conductive layer is closer to the transparent conductive layer than the second conductive layer; wherein, the first conductive layer is a metal conductive layer, and the second conductive layer is a metal protective layer.

[0016] Optionally, the composite metal conductive layer is disposed on the transparent conductive layer.

[0017] Optionally, the back side of the battery cell substrate has alternately arranged N-type conductive regions and P-type conductive regions, and the transparent conductive layer and the composite conductive layer are stacked in the N-type conductive regions and P-type conductive regions and separated by an isolation groove, which is achieved by etching the composite conductive layer and the transparent conductive layer;

[0018] The ratio of the width of the composite conductive layer to the width of the isolation groove is 3:1 to 10:1.

[0019] Optionally, the material of the first conductive layer is one of copper, tin or silver; when the first conductive layer is tin or silver, the second conductive layer is not provided.

[0020] The material of the second conductive layer includes at least one of tin, silver, and nickel; or, the second conductive metal layer is one of an indium oxide film, a doped tin oxide film, or a doped zinc oxide film.

[0021] Optionally, the thickness of the transparent conductive layer is 10 nm to 200 nm; the thickness of the composite metal layer is 70 nm to 550 nm; the thickness of the first conductive layer is 50 nm to 450 nm; and the thickness of the second conductive layer is 20 nm to 100 nm.

[0022] And / or, the material of the transparent conductive layer includes at least one of a doped indium oxide film, a tungsten-doped indium oxide film, a doped tin oxide film, or a doped zinc oxide film.

[0023] Optionally, the material of the fine grid electrode includes low-temperature silver paste or silver-copper paste; or, the fine grid electrode is an electroplated copper grid metal electrode.

[0024] The main grid electrode is made of low-temperature silver paste or silver-copper paste.

[0025] Optionally, the insulating layer is made of insulating adhesive; and / or, the thickness of the insulating layer is 5 μm to 50 μm.

[0026] Secondly, embodiments of this disclosure also provide a method for fabricating a back-contact solar cell, configured to fabricate a back-contact solar cell as described in the first aspect, comprising:

[0027] A solar cell substrate is provided; the back side of the solar cell substrate has alternately arranged N-type conductive regions and P-type conductive regions.

[0028] A transparent conductive film layer and a composite conductive film layer are sequentially prepared on the back side of the battery cell substrate;

[0029] The transparent conductive film layer and the composite conductive film layer located at the junction of the N-type conductive region and the P-type conductive region are removed by a patterning process, thereby forming an isolation groove and the transparent conductive layer and the composite conductive layer stacked in the N-type conductive region and the P-type conductive region;

[0030] Fine grid electrodes, insulating layers, and main grid electrodes are sequentially fabricated on a solar cell substrate with isolation grooves.

[0031] Optionally, the step of sequentially fabricating a fine grid electrode, an insulating layer, and a main grid electrode on the battery cell substrate with the isolation trench includes:

[0032] The fine gate electrode of the low-temperature silver paste material is fabricated by screen printing or pad printing, or by electroplating copper fine gate. When the polarity of the main gate electrode and the fine gate electrode are the same, the fine gate electrode remains continuous. When the polarity of the main gate electrode and the fine gate electrode are different, the fine gate electrode is pre-broken in the area overlapping with the main gate electrode, and the break length of the fine gate electrode is 0.1 mm to 10 mm.

[0033] An insulating layer is fabricated in the area where the fine gate electrode is broken using screen printing, pad printing, or inkjet printing. The dimension of the insulating layer along the second direction is 1.1 to 1.5 times the length of the break in the fine gate electrode; the dimension of the insulating layer along the first direction is 1.1 to 1.5 times the width of the composite conductive layer.

[0034] The main gate electrode is fabricated on the insulating layer using screen printing or pad printing. The main gate electrode covers the insulating layer and is connected to the fine gate electrode of the same polarity.

[0035] Thirdly, embodiments of this disclosure also provide a method for fabricating a back-contact solar cell, configured to fabricate a back-contact solar cell as described in the first aspect, comprising:

[0036] A solar cell substrate is provided; the back side of the solar cell substrate has alternately arranged N-type conductive regions and P-type conductive regions.

[0037] A transparent conductive film layer and a composite conductive film layer are sequentially prepared on the back side of the battery cell substrate;

[0038] An isolation trench is fabricated on the back of the battery cell substrate at the junction of the N-type conductive region and the P-type conductive region using a patterning process, so as to form a transparent conductive layer and a composite conductive layer separated by the isolation trench.

[0039] Fine grid electrodes and an insulating layer are sequentially fabricated on a battery substrate with pre-fabricated isolation trenches;

[0040] The main gate electrode is fabricated along a direction perpendicular to the fine gate electrode.

[0041] Fourthly, embodiments of this disclosure also provide a battery assembly including a back-contact solar cell as described in the first aspect.

[0042] The embodiments disclosed herein have at least the following beneficial effects:

[0043] This disclosure, through the above-described technical solution, eliminates the portion of the fine grid electrode in the overlapping area of ​​the main grid electrode and the fine grid electrode by adopting a hybrid metal electrode structure. It replaces the traditional fine grid electrode with a metal composite layer beneath the fine grid electrode, avoiding spatial cross-structures between the fine grid electrode and the main grid electrode. This reduces short-circuit defects caused by insufficient effective insulation thickness, thus improving battery yield. Furthermore, it limits the discontinuity length of the fine grid electrode to the width of the main grid electrode, providing a more ample error range for soldering. By limiting the ratio between the thickness of the composite conductive layer and its width in the first direction, it helps ensure the linear resistivity of the composite conductive layer, preventing excessively high resistivity from causing additional power loss. In addition, replacing the fine grid electrode with a flat composite conductive layer allows for a significant reduction in the thickness of the insulating layer, saving on insulation material costs. Attached Figure Description

[0044] To more clearly illustrate the technical solutions of the embodiments of this disclosure, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of this disclosure and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0045] Figure 1 is a top view of the internal structure of a back-contact solar cell provided in an embodiment of this disclosure;

[0046] Figure 2 is a partial cross-sectional schematic diagram of a back-contact solar cell provided in an embodiment of this disclosure;

[0047] Figure 3 is a cross-sectional view of a back-contact solar cell along the direction of the fine grid electrode provided in an embodiment of this disclosure;

[0048] Figure 4 is a cross-sectional view of a back-contact solar cell along the main grid electrode direction provided in an embodiment of this disclosure;

[0049] Figure 5 is a cross-sectional view along the main grid electrode direction of another back-contact solar cell provided in an embodiment of this disclosure;

[0050] Figure 6 is a schematic flowchart of a method for fabricating a back-contact solar cell according to an embodiment of this disclosure;

[0051] Figure 7 is a schematic diagram of the process structure along the first and second directions in step S100 of a method for fabricating a back contact solar cell according to an embodiment of this disclosure.

[0052] Figure 8 is a schematic diagram of the process structure along the first and second directions in step S200 of a method for fabricating a back contact solar cell according to an embodiment of the present disclosure.

[0053] Figure 9 is a schematic diagram of the process structure along the first direction in step S300 of a method for fabricating a back-contact solar cell according to an embodiment of this disclosure;

[0054] Figure 10 is a schematic diagram of the process structure along the first direction in steps S400 and S500 of a method for fabricating a back contact solar cell according to an embodiment of the present disclosure.

[0055] Figure 11 is a schematic diagram of the process structure along the second direction in steps S400 and S500 of a back contact solar cell fabrication method provided in this embodiment of the present disclosure.

[0056] Figure 12 is a schematic flowchart of another method for fabricating a back-contact solar cell provided in an embodiment of this disclosure;

[0057] Figure 13 is a schematic diagram of the process structure along the first and second directions in step S1 of a method for fabricating a back contact solar cell according to an embodiment of the present disclosure.

[0058] Figure 14 is a schematic diagram of the process structure along the first and second directions in step S2 of a method for fabricating a back contact solar cell according to an embodiment of the present disclosure.

[0059] Figure 15 is a schematic diagram of the process structure along the first direction in step S3 of a method for fabricating a back-contact solar cell according to an embodiment of this disclosure.

[0060] Figure 16 is a schematic diagram of the process structure along the first direction in step S4 of a method for fabricating a back-contact solar cell according to an embodiment of this disclosure.

[0061] Figure 17 is a schematic diagram of the process structure along the second direction in step S4 of a method for fabricating a back-contact solar cell according to an embodiment of this disclosure;

[0062] Figure 18 is a schematic diagram of the process structure along the first direction in step S5 of a method for fabricating a back-contact solar cell according to an embodiment of this disclosure;

[0063] Figure 19 is a schematic diagram of the process structure along the second direction in step S5 of a method for fabricating a back-contact solar cell according to an embodiment of this disclosure;

[0064] Figure 20 is a schematic diagram of the process structure along the first direction in step S51 of a method for fabricating a back-contact solar cell according to an embodiment of this disclosure;

[0065] Figure 21 is a schematic diagram of the process structure along the first direction in step S6 of a method for fabricating a back-contact solar cell according to an embodiment of this disclosure;

[0066] Figure 22 is a schematic diagram of the process structure along the second direction in step S6 of a method for fabricating a back-contact solar cell according to an embodiment of this disclosure;

[0067] Figure 23 is a schematic diagram of a cross-section of a conventional back-contact solar cell;

[0068] Figure 24 is a schematic cross-sectional view of a back-contact solar cell provided in an embodiment of this disclosure.

[0069] Explanation of reference numerals in the attached figures: 1-Battery cell substrate; 2-Transparent conductive layer; 2n-Transparent conductive layer of N-type conductive region; 2p-Transparent conductive layer of P-type conductive region; 2g-Isolation region; 3-Composite conductive layer; 4a-Fine grid electrode; 4b-Main grid electrode; 5-Insulating layer. Detailed Implementation

[0070] In this disclosure, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this disclosure, "a plurality of" means two or more, unless otherwise explicitly specified.

[0071] In this disclosure, unless otherwise expressly specified and limited, "above" or "below" the second feature can mean that the first and second features are in direct contact, or that the first and second features are in indirect contact through an intermediate medium. Furthermore, "above," "on top of," and "over" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0072] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the ranges, the endpoint values ​​of the ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein. The terms "optional" and "discretionary" mean that they may or may not be included (or may or may not be present).

[0073] In a first aspect, referring to Figures 1 to 4, embodiments of this disclosure provide a back-contact solar cell, comprising: a cell substrate 1, a transparent conductive layer 2, a composite conductive layer 3, a fine grid electrode 4a, an insulating layer 5, and a main grid electrode 4b.

[0074] Specifically, the solar cell substrate 1 has a front side and a back side; the front side refers to the light-receiving surface of the solar cell substrate 1, and the back side is the opposite side of the light-receiving surface. In this embodiment, the area closer to the solar cell substrate 1 is generally considered as the inside, and the area farther from the solar cell substrate 1 is considered as the outside. The back side of the solar cell substrate 1 has alternately arranged N-type conductive regions and P-type conductive regions. Specifically, the N-type conductive regions and P-type conductive regions are arranged alternately along the first direction in Figure 1, and there is an isolation region 2g between the N-type conductive regions and the P-type conductive regions. The length extension direction of the N-type conductive regions and the P-type conductive regions is a second direction, which is perpendicular to the first direction.

[0075] A transparent conductive layer 2 is disposed on the back side of the solar cell substrate 1. The transparent conductive layer 2 can be made of ITO (Indium Tin Oxide), which has good light transmittance and conductivity, which is beneficial to improving photoelectric conversion efficiency. A composite conductive layer 3 is disposed on the side of the transparent conductive film layer away from the solar cell substrate 1. That is, the composite conductive layer 3 and the transparent conductive layer 2 are stacked on the back side of the solar cell and separated by an isolation trench. The isolation trench is located in the region where the isolation region 2g is located, and is mainly configured to separate the N-type conductive region and the P-type conductive region to form a semiconductor structure with a PN junction. The ratio of the width of the composite conductive layer 3 to the width of the isolation trench is 3:1 to 10:1. Etching separates the transparent conductive layer 2 and the composite conductive layer 3 to prevent the connection between the N-type and P-type conductive regions. In principle, the smaller the width of the isolation trench, the better. Empirically, the ratio of the width of the composite conductive layer 3 (at the fine gate break position) to the width of the isolation trench is between 3:1 and 10:1. Too small a width of the isolation trench will lead to a lower process yield, while too large a width will result in a narrower conductive layer, leading to power loss in current transmission. The transparent conductive layer 2 located in the N-type conductive region is designated as N-type conductive layer 2n, and the transparent conductive layer located in the P-type conductive region is designated as N-type conductive layer 2p, for easy distinction in the diagram.

[0076] The fine grid electrode 4a is disposed on the side of the composite conductive layer 3 away from the cell substrate 1. The main grid electrode 4b and the fine grid electrode 4a are approximately out-of-plane straight lines and are perpendicular to each other. In the region where they are perpendicularly distributed, the fine grid electrode 4a is intermittently disposed, that is, the portion of the fine grid electrode 4a that is not perpendicularly distributed is electrically connected through the underlying composite conductive layer 3. The insulating layer 5 at least fills the intermittent region of the fine grid electrode 4a to isolate the composite conductive layer 3 from the main grid electrode 4b in this region.

[0077] The composite conductive layer 3 includes: a first conductive layer and / or a second conductive layer stacked together; the first conductive layer is closer to the transparent conductive layer 2 than the second conductive layer; wherein, the first conductive layer is a metal conductive layer, mainly providing the main conductive layer, and should be as thick as possible; the second conductive layer is a metal protective layer, mainly configured to protect the underlying first conductive layer, and only needs to prevent oxidation of the first conductive layer, and its thickness is relatively thin. Optionally, the thickness of the composite metal layer is 70nm to 550nm, the thickness of the first conductive layer is 50nm to 450nm, and the thickness of the second conductive layer is 20nm to 100nm.

[0078] The transparent conductive film layer and the composite conductive layer 3 are fabricated using physical vapor deposition (PVD) or reactive plasma deposition (RPD).

[0079] When preparing the transparent conductive film layer and the composite conductive film layer, the substrate temperature range is 100℃~250℃, preferably 180℃~220℃.

[0080] In this embodiment, the relationship between the width of the composite conductive layer 3 along the first direction and its own thickness is: the ratio between the thickness of the composite conductive layer 3 and the width of the composite conductive layer 3 in the first direction satisfies the formula ρ. l =ρ0 / (b*h), where ρ l Let ρ0 be the linear resistivity of the composite conductive layer 3 along the second direction, ρb be the bulk resistivity of the composite conductive layer 3, b be the width of the composite conductive layer 3 along the first direction, and h be the thickness of the composite conductive layer 3. The linear resistivity ρ0 is... l The range is 0.5 to 3.5 Ω / cm; wherein, the first direction is the length extension direction of the main gate electrode 4b, and the second direction is the length extension direction of the fine gate electrode 4a.

[0081] Optionally, the linear resistivity ρ l The range is 1.0 to 2.5 Ω / cm, ensuring that the resistivity of the composite conductive layer 3 replacing the fine grid lines reaches an appropriate range, avoiding additional power loss due to excessive resistance in this area, which would reduce battery efficiency; if the resistivity is too low, there will be less resistance, but it will not have a significant effect on improving efficiency, and will instead increase costs.

[0082] The back-contact solar cell provided in this embodiment employs a hybrid metal electrode structure, eliminating the portion of the fine grid electrode 4a in the vertically divided area of ​​the main grid electrode 4b and the fine grid electrode 4a, and replacing the traditional fine grid electrode 4a with a metal composite layer below the fine grid electrode 4a. This avoids the spatial intersection structure between the fine grid electrode 4a and the main grid electrode 4b, thereby increasing the effective insulation thickness and reducing short-circuit defects caused by insufficient effective insulation thickness, which is beneficial to improving the yield of the cell. At the same time, the discontinuity length of the fine grid electrode 4a and the width of the main grid electrode 4b are limited, providing a more ample error range for soldering. Furthermore, by limiting the ratio between the thickness of the composite conductive layer 3 and the width of the composite conductive layer 3 in the first direction, the linear resistivity of the composite conductive layer 3 is better ensured, avoiding additional power loss due to excessively high resistivity. In addition, replacing the fine grid electrode 4a with a flat composite conductive layer 3 allows for a significant reduction in the thickness of the insulating layer 5, saving material costs for the insulating layer 5.

[0083] In some embodiments, referring to Figure 5, the composite conductive layer 3 is not provided in the area not covered by the fine grid electrode 4a, insulating layer 5, and main grid electrode 4b. That is, the composite conductive layer 3 in the area of ​​the transparent conductive layer 2 not covered by the fine grid electrode 4a, insulating layer 5, and main grid electrode 4b is removed, and only the composite conductive layer 3 in the area covered by the fine grid electrode 4a, insulating layer 5, and main grid electrode 4b is retained. This reduces the absorption of sunlight by this part of the composite conductive layer 3, especially the absorption of near-infrared wavelengths, thereby increasing the reflectivity of light and increasing the short-circuit current of the back-contact solar cell. The specific mechanism is that solar cells with a metal layer on the back of the cell substrate 1, especially when a metal layer is used on the back, have significant absorption of infrared and near-infrared wavelengths, resulting in a significant reduction in the reflection of infrared and near-infrared wavelengths on the back of the cell, thus reducing the short-circuit current of the solar cell. Removing the excess of this composite metal layer while retaining the transparent conductive layer 2 can reduce this loss.

[0084] Optionally, the first conductive layer is made of copper, which is beneficial for improving conductivity.

[0085] Optionally, the material of the second conductive layer includes at least one of tin, silver, and nickel. When the material of the second conductive layer is silver, since silver can contact the covering silver paste, it prevents the underlying copper from oxidizing. On the other hand, silver has better compatibility with the material of the fine gate electrode 4a (e.g., silver paste), which is beneficial to improving the adhesion between the film layers.

[0086] Optionally, when the first conductive layer is tin or silver, the composite conductive layer 3 may not have a second conductive layer.

[0087] In some other embodiments, the second conductive metal layer is one of an indium oxide film layer (such as tin-doped indium oxide ITO, tungsten-doped indium oxide IWO, IZO, etc.), a doped tin oxide film layer (such as FTO, ATO, etc.), or a doped zinc oxide film layer (such as GZO, AZO, etc.).

[0088] Optionally, the material of the transparent conductive layer 2 includes at least one of a doped indium oxide film, a tungsten-doped indium oxide film, a doped tin oxide film, or a doped zinc oxide film.

[0089] In some embodiments, the material of the fine gate electrode 4a includes low-temperature silver paste or silver-copper paste. Optionally, the fine gate electrode 4a is an electroplated copper gate metal electrode.

[0090] In some embodiments, the insulating layer 5 is made of insulating adhesive. Optionally, the thickness of the insulating layer 5 is 5 μm to 50 μm.

[0091] In some embodiments, the main gate electrode 4b is made of low-temperature silver paste or silver-copper paste.

[0092] Secondly, as shown in Figure 6, this disclosure provides a method for fabricating a back-contact solar cell, configured to fabricate the back-contact solar cell described in the first aspect, comprising the following steps:

[0093] S100, a battery cell substrate 1 is provided; the back side of the battery cell substrate 1 has alternately arranged N-type conductive regions and P-type conductive regions, as shown in Figure 7.

[0094] S200, a transparent conductive film layer and a composite conductive film layer are sequentially prepared on the back side of the battery cell substrate 1, as shown in Figure 8.

[0095] S300, the transparent conductive film layer and the composite conductive film layer located at the junction of the N-type conductive region and the P-type conductive region are removed by a patterning process, thereby forming an isolation groove and a transparent conductive layer 2 and a composite conductive layer 3 stacked in the N-type conductive region and the P-type conductive region, as shown in Figures 9 and 8.

[0096] S400, a fine grid electrode 4a, an insulating layer 5, and a main grid electrode 4b are sequentially fabricated on a battery cell substrate 1 with an isolation groove, as shown in Figures 10 and 11.

[0097] Specifically, the fine gate electrode 4a is first fabricated using methods such as screen printing or pad printing, or by electroplating copper fine gates. Its characteristics are as follows: the fine gate electrode 4a is designed at the reserved position for the main gate electrode 4b as follows: when the polarity of the main gate electrode 4b is the same as that of the fine gate electrode 4a, the fine gate electrode 4a needs to be continuous; when the polarity of the main gate electrode 4b is different from that of the fine gate electrode 4a, the fine gate electrode 4a is pre-broken in the area overlapping with the main gate electrode 4b, and the break length is 0.1 mm to 10 mm. The break length of the fine gate electrode 4a is 1.2 to 10 times the width of the main gate electrode 4b, preferably 1.2 to 5 times.

[0098] Then, the insulating layer 5 is made by means of screen printing, pad printing, inkjet printing, etc. The length of the insulating layer 5 (i.e. the dimension along the second direction) needs to be greater than the length of the break of the fine gate electrode 4a, preferably 1.1 to 1.5 times the length of the break of the fine gate electrode 4a; the width of the insulating layer 5 (i.e. the dimension along the first direction) needs to be greater than the width of the composite conductive layer 3, preferably 1.1 to 1.5 times the width of the composite conductive layer 3.

[0099] Finally, the main gate electrode 4b of the low-temperature silver paste material is made by screen printing, pad printing and other methods. Its feature is that it covers the insulating layer 5 and is connected to the fine gate electrode 4a of the same polarity.

[0100] Optionally, after step S400, the method further includes:

[0101] S500, remove the composite conductive layer 3 that is not covered by the fine gate electrode 4a, the insulating layer 5, and the main gate electrode 4b. Specifically, referring to Figures 10 and 11, the composite conductive layer 3 can be removed by step etching. First, a hydrochloric acid solution with a weight ratio of 0.05-0.5% is used to remove the second conductive layer on the surface of the composite conductive layer 3. Then, an alkaline etching solution, such as a mixed solution of copper chloride, ammonium chloride, ammonia, and hydrogen peroxide, with a weight ratio of 10%-15% copper chloride, 5%-10% ammonium chloride, 10%-50% ammonia, 1%-20% hydrogen peroxide, and the remainder being water, is used to remove the exposed portion of the composite conductive layer 3.

[0102] Optionally, in the process of removing the composite conductive layer 3 by step corrosion, when the first conductive layer is copper, the solution for removing the first conductive layer in the uncovered area can also be replaced by a ferric ion solution, such as ferric chloride solution or ferric sulfate solution. The concentration is set according to the actual corrosion rate, and this embodiment does not impose specific limitations.

[0103] In addition, this embodiment can also use a solution method to remove the composite conductive layer 3. An acidic etching solution can be used to remove the exposed part of the composite conductive layer 3 in one go, such as a sulfuric acid and hydrogen peroxide mixed solution, with the sulfuric acid weight ratio being 0.05% to 5% and the hydrogen peroxide weight ratio being 0.01% to 5%. However, the acidic solution also has a strong corrosive ability on the transparent conductive layer 2, and the difference in corrosion rate needs to be controlled to manage the time window.

[0104] Alternatively, the transparent conductive film layer and the composite conductive layer 3 can be prepared by magnetron sputtering (PVD), reactive plasma deposition (RPD), or vapor deposition.

[0105] Alternatively, the isolation tank can be manufactured by etching paste etching or solution etching.

[0106] Specifically, the etching paste etching method is as follows: at the junction of the N-type conductive area and the P-type conductive area, the etching paste is applied for etching. The application method is screen printing, inkjet printing, dispensing, etc. The composite conductive layer 3 and the transparent conductive layer 2 in the coated area are etched away by baking. Then the residual etching paste is removed by cleaning.

[0107] The solution etching method is as follows: A mask layer is fabricated on the surface of the solar cell substrate 1. The mask pattern exposes the underlying composite conductive layer 3 and transparent conductive film layer at the boundary between the N-type and P-type conductive regions, while covering other areas. The composite conductive layer 3 and transparent conductive film layer are then etched using an etching solution. Finally, the mask layer is removed. The mask layer is made of photosensitive emulsion, dry film, and protective ink. The mask layer is fabricated by spin coating / lamination, exposure, and development; or by screen printing, inkjet printing, and dispensing.

[0108] Optionally, the etching solution includes an acidic etching solution and / or an alkaline etching solution. Etching can be performed using a single acidic or alkaline etching solution, or a combination of both, depending on the configuration of the composite metal layer. The acidic etching solution includes at least one of hydrochloric acid, sulfuric acid, nitric acid, sodium hypochlorite, hydrogen peroxide, and ferric chloride; the alkaline etching solution includes at least one of copper chloride, ammonia, and ammonium chloride.

[0109] Optionally, after step S400, the composite conductive layer 3, which is not covered by the fine grid electrode 4a, the insulating layer 5, and the main grid electrode 4b, can also be retained in the battery to save process steps.

[0110] Thirdly, as shown in Figure 12, this disclosure provides another method for fabricating a back-contact solar cell, configured to fabricate the back-contact solar cell described in the first aspect, comprising the following steps:

[0111] S1, a battery cell substrate 1 is provided; the back side of the battery cell substrate 1 has alternately arranged N-type conductive regions and P-type conductive regions, as shown in Figure 13.

[0112] S2, a transparent conductive film layer and a composite conductive film layer are sequentially prepared on the back side of the battery cell substrate 1, as shown in Figure 14.

[0113] S3, using a patterning process, an isolation groove is formed on the back of the battery cell substrate 1 at the junction of the N-type conductive region and the P-type conductive region to form a transparent conductive layer 2 and a composite conductive layer 3 separated by the isolation groove, as shown in Figure 15.

[0114] S4. Fine grid electrodes 4a are sequentially fabricated on the battery substrate with the pre-fabricated isolation trench, as shown in Figures 16 and 17.

[0115] S5, an insulating layer 5 is provided at the discontinuous positions of the fine grid metal electrode, as shown in Figures 18 and 19.

[0116] Specifically, the method for preparing the fine gate electrode 4a is the same as the method in step S400 of the aforementioned embodiment, and will not be described in detail here.

[0117] S6. The main gate electrode 4b is fabricated along the direction perpendicular to the fine gate electrode 4a, as shown in Figures 21 and 22.

[0118] Specifically, the preparation method of the main gate electrode 4b is the same as that of step S400 in the aforementioned embodiment, and will not be described in detail here.

[0119] Optionally, the process may further include the following steps between S5 and S6:

[0120] S51, remove the composite conductive layer 3 that is not covered by the fine gate electrode 4a and the insulating layer 5, and continue to refer to the process structure schematic diagrams shown in FIG20 (first direction) and FIG19 (second direction).

[0121] In this embodiment, removing the composite conductive layer 3 not covered by the fine grid electrode 4a and the insulating layer 5 can reduce the free carrier absorption effect (FCA) of the metal layer, thereby reducing the loss of infrared absorption by the back metal film layer; it can also increase the bifaciality of the battery and increase the power generation efficiency on the back side. Furthermore, it should be noted that the specific process for removing the composite conductive layer 3 not covered by the fine grid electrode 4a and the insulating layer 5 can refer to step S500 in the aforementioned embodiment, and will not be described in detail here.

[0122] The back-contact solar cell fabricated using the method provided in this embodiment does not have a metal conductive layer in the area other than the fine grid electrode 4a, the insulating layer 5, and the main grid electrode 4b. This avoids the absorption of sunlight by the metal layer, increases the reflectivity of light, and thus increases the short-circuit current of the back-contact solar cell. Specifically, the mechanism is that solar cells with a metal layer on the back of the cell substrate 1, especially when a copper metal layer is used, exhibit significant absorption in the infrared and near-infrared bands, resulting in a significant reduction in infrared reflection from the back of the cell, thereby lowering the short-circuit current. Removing this excess composite metal layer while retaining the transparent conductive layer 2 reduces this loss.

[0123] Fourthly, embodiments of this disclosure provide a battery module including the back-contact solar cell of the foregoing embodiments. The back-contact solar cell of this battery module employs a hybrid metal electrode structure, eliminating the portion of the fine grid electrode in the overlapping area of ​​the main grid electrode and the fine grid electrode, and replacing the traditional fine grid electrode with a metal composite layer beneath the fine grid electrode. This avoids spatial cross-structures between the fine grid electrode and the main grid electrode, reducing short-circuit defects caused by insufficient effective insulation thickness, and improving battery yield. Simultaneously, replacing the fine grid electrode with a flat composite conductive layer allows for a significant reduction in the thickness of the insulating layer, saving on insulation material costs.

[0124] As shown in Figure 23, in a conventional back-contact battery where an insulating layer is used to insulate the main grid electrode and the fine grid electrode, the fine grid electrode and the main grid electrode are continuous in the overlapping area of ​​the main grid electrode and the fine grid electrode. Therefore, the fine grid electrode and the main grid electrode are spatially intersected, and the insulation is achieved entirely by filling the gap with insulating layer material. This results in the actual effective insulation thickness (i.e., the spatial distance between the main grid electrode and the fine grid electrode) being equal to the difference between the insulation layer thickness and the fine grid electrode thickness. For example, if the insulation layer thickness is 30 μm (the insulation layer is printed on the back of the battery substrate, covering the fine grid electrode, and its thickness is measured from the distance between the substrate surface and the highest point of the insulation layer), and the fine grid electrode thickness is 20 μm, then the effective insulation thickness is 10 μm. In particular, when the fine grid electrode is a screen-printed silver paste electrode, since screen-printed electrodes always have an undulating shape, for example, a 20μm thick silver paste electrode may have a minimum thickness of less than 15μm and a maximum thickness of 25μm. When the highest point of the undulation of the fine grid electrode is located at the position of the main grid electrode, the effective insulation thickness of the insulating layer is 5μm.

[0125] As shown in Figure 24, this embodiment proposes to use a composite conductive layer to replace the fine gate electrode. The composite conductive layer, which is made by film deposition, is almost as flat as the substrate (and its surface does not have fine gate electrodes). Therefore, the actual thickness of the insulating layer is equal to the effective thickness of the insulating layer (which is equivalent to increasing the effective thickness of the insulating layer). Taking the insulating layer thickness of 30 μm mentioned above as an example, after using the flat composite conductive layer structure, the insulating layer thickness is reduced to 15 μm, which can significantly reduce the amount of insulating material. At the same time, the 15 μm insulating layer thickness is the effective insulation thickness, which is also greater than the effective insulation thickness of the fine gate continuous structure.

[0126] The embodiments of this disclosure described below are exemplary and are only used to explain this disclosure, and should not be construed as limiting this disclosure.

[0127] Example 1

[0128] A back-contact solar cell, the structure of which is shown in Figures 1 to 4, includes: a cell substrate; a transparent conductive layer disposed on the back side of the cell substrate; a composite conductive layer disposed on the side of the transparent conductive layer away from the cell substrate; a fine grid electrode disposed on the side of the composite conductive layer away from the cell substrate; a main grid electrode; and an insulating layer. The main grid electrode and the fine grid electrode overlap perpendicularly to each other, and the fine grid electrode is intermittently disposed in the region of the perpendicular overlap. The peak height of the fine grid electrode is 15 μm. The insulating layer at least fills the intermittent region of the fine grid electrode to isolate the composite conductive layer from the main grid electrode. The transparent conductive layer has a thickness of 60 nm, the composite conductive layer has a thickness of 300 nm, and the insulating layer has a thickness of 20 μm. The width of the composite conductive layer ranges from 500 μm. This thickness setting results in an effective insulating thickness equal to the insulating layer thickness of 20 μm.

[0129] Optionally, the composite conductive layer includes a first conductive layer and a second conductive layer stacked together, with the first conductive layer being closer to the transparent conductive layer than the second conductive layer; wherein, the first conductive layer is a metallic copper conductive layer, the second conductive layer is an ITO protective layer, the thickness of the first conductive layer is 250nm, and the thickness of the second conductive layer is 50nm. This arrangement can ensure that the conductivity of the composite conductive layer region is appropriate, and can replace the metal fine gate electrode for conduction while avoiding significant power loss.

[0130] Example 2

[0131] Referring to the back-contact solar cell structure of Example 1, the difference is that the thickness of the first conductive layer is increased to 350 nm, and the width of the composite conductive layer is adjusted to 300 μm. Example 2 is an example of increasing the thickness of the conductive layer and reducing the width of the conductive area. This will lead to an increase in the area of ​​the isolation trench and a reduction in the short-circuit current I sc, but a slight increase in FF due to the increase in the number of conductive areas.

[0132] Example 3

[0133] Referring to the back-contact solar cell structure of Example 1, the difference is that the thickness of the composite conductive layer is reduced to 150nm, and the width of the composite conductive layer is adjusted to 700μm. Example 3 is an example of reducing the thickness of the conductive layer and increasing the width of the conductive region. This will result in a reduction in the number of conductive regions, a larger current density in each conductive region, and increased power loss, resulting in lower Isc and lower FF.

[0134] Example 4

[0135] Referring to the back-contact solar cell structure of Example 1, the difference is that, without changing the total thickness of the composite conductive layer, the thickness of the first conductive layer is adjusted to 200 nm and the thickness of the second conductive layer is 100 nm. Example 4 is an example of reducing the thickness of the first conductive layer, which will lead to an increase in the resistance of the conductive layer and thus an increase in power loss, an increase in Rs and a decrease in FF.

[0136] Example 5

[0137] Referring to the back-contact solar cell structure of Example 1, the difference is that, without changing the total thickness of the composite conductive layer, the thickness of the first conductive layer is adjusted to 280 nm and the thickness of the second conductive layer is 20 nm. Example 5 is an example of increasing the thickness of the first conductive layer and decreasing the thickness of the protective layer. Due to insufficient protection, the conductive layer is oxidized, which increases the transmission resistance and thus increases the power loss. Its FF is slightly better than that of Example 4, but lower than that of Example 1.

[0138] Example 6

[0139] Referring to the back contact solar cell structure of Example 1, the difference is that the thickness of the first conductive layer is kept unchanged, while the thickness of the second conductive layer is reduced to 20nm. Example 6 is an example of reducing the thickness of the protective layer. Due to insufficient protection, the conductive layer is oxidized, which increases the transmission resistance and thus increases the power loss. Its FF is slightly better than that of Example 4, but lower than that of Example 1.

[0140] Example 7

[0141] Referring to the back contact solar cell structure of Example 1, the difference is that the thickness of the first conductive layer is kept unchanged, and the thickness of the second conductive layer is increased by 100nm. In Example 7, the thickness of the protective layer (I TO) is increased. The increase in thickness will lead to an increase in the longitudinal transmission distance, but will increase the series resistance and the FF will be slightly lower.

[0142] Example 8

[0143] Referring to the back-contact solar cell structure of Example 1, the difference is that the composite metal layer outside the area covered by the fine grid electrode and the insulating layer is retained. In Example 8, the metal layer outside the coverage area is retained, which will result in a significant decrease in Isc, but an increase in FF.

[0144] Comparative Example 1

[0145] Referring to the back contact solar cell structure of Example 1, the difference is that no composite conductive layer is set, and the entire fine grid electrode is directly set on the transparent conductive layer. Comparative Example 1 uses a silver paste fine grid through design, which has insufficient effective insulation thickness, resulting in a low Rsh and a significant decrease in reverse dark current yield.

[0146] Comparative Example 2

[0147] Referring to the back contact solar cell structure of Example 1, the difference is that the thickness of the first conductive layer is 40nm. In Comparative Example 2, the first conductive layer in the composite conductive layer is set too thin, resulting in a significant increase in Rs and a significant decrease in FF, and a significant decrease in efficiency, but Rsh and reverse dark current are normal.

[0148] Comparative Example 3

[0149] Referring to the back contact solar cell structure of Example 1, the difference is that the width of the composite conductive layer is 1000μm. In Comparative Example 3, the composite conductive layer is too wide (i.e., the conductive area is too wide), and the cell's efficiency drops significantly due to carrier transport loss, but the Rsh and reverse dark current are normal.

[0150] Comparative Example 4

[0151] Referring to the back-contact solar cell structure of Comparative Example 1, the difference is that the insulation layer thickness is set to 30μm, and the fine grid electrode is directly set on the transparent conductive layer. Comparative Example 4 refers to Comparative Example 1, and while adopting the silver paste fine grid through design, the thickness of the insulating ink is increased. Although this can achieve a higher efficiency level and alleviate the problems of low Rsh and low reverse dark current yield to a certain extent, the yield will not reach a high level due to the random variation in the thickness of the insulating ink.

[0152] The performance data of the back-contact solar cells obtained from the above embodiments and comparative examples are shown in the table below:

[0153] Table 1 Comparison of battery performance data from different embodiments and comparative examples

[0154] The above results show that, compared to the comparative example, the embodiment of this disclosure effectively avoids battery short circuits caused by poor insulation of the insulating layer. This is reflected in a significantly improved parallel resistance Rsh and a significantly improved reverse dark current yield, which is beneficial for improving battery production yield. Optionally, as shown in Embodiments 1 and 2-7, using the preferred composite conductive film with an appropriate thickness and width can further reduce the power loss of the composite conductive layer, which is more conducive to further improving battery efficiency.

[0155] The preferred embodiments of this disclosure have been described in detail above; however, this disclosure is not limited thereto. Within the scope of the technical concept of this disclosure, various simple modifications can be made to the technical solutions of this disclosure, including combining the various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in this disclosure and are all within the protection scope of this disclosure. Industrial applicability

[0156] This disclosure, through the above-described technical solution, eliminates the portion of the fine grid electrode in the overlapping area of ​​the main grid electrode and the fine grid electrode by adopting a hybrid metal electrode structure. It replaces the traditional fine grid electrode with a metal composite layer beneath the fine grid electrode, avoiding spatial cross-structures between the fine grid electrode and the main grid electrode. This reduces short-circuit defects caused by insufficient effective insulation thickness, thus improving battery yield. Furthermore, it limits the discontinuity length of the fine grid electrode to the width of the main grid electrode, providing a more ample error range for soldering. By limiting the ratio between the thickness of the composite conductive layer and its width in the first direction, it helps ensure the linear resistivity of the composite conductive layer, preventing excessively high resistivity from causing additional power loss. In addition, replacing the fine grid electrode with a flat composite conductive layer allows for a significant reduction in the thickness of the insulating layer, saving on insulation material costs.

Claims

1. A back-contact solar cell, characterized in that, include: Solar cell substrate; A transparent conductive layer is disposed on the back side of the battery cell substrate; A composite conductive layer is disposed on the side of the transparent conductive film layer away from the battery cell substrate; A fine grid electrode is disposed on the side of the composite conductive layer away from the cell substrate; The main gate electrode and the fine gate electrode overlap perpendicularly to each other, and the fine gate electrode is intermittently arranged in the area of ​​the perpendicular overlap. The intermittent length of the fine gate electrode is 0.1 to 10 mm. The insulating layer at least fills the intermittent area of ​​the fine gate electrode to isolate the composite conductive layer from the main gate electrode. The ratio between the thickness of the composite conductive layer and the width of the composite conductive layer along the first direction satisfies the formula ρ. l =ρ0 / (b*h), where ρ l Let ρ0 be the linear resistivity of the composite conductive layer along the second direction, ρb be the bulk resistivity of the composite conductive layer, b be the width of the composite conductive layer along the first direction, and h be the thickness of the composite conductive layer. The linear resistivity ρ0 is the linear resistivity of the composite conductive layer. l The range is 0.5 to 3.5 Ω / cm; wherein, the first direction is the length extension direction of the main gate electrode, and the second direction is the length extension direction of the fine gate electrode; The composite conductive layer has a thickness of 70nm to 550nm; the composite conductive layer includes: a first conductive layer and / or a second conductive layer stacked together, the first conductive layer having a thickness of 50nm to 450nm, and the second conductive layer having a thickness of 20nm to 100nm; the first conductive layer is closer to the transparent conductive layer than the second conductive layer; wherein, the first conductive layer is a metal conductive layer, and the second conductive layer is a metal protective layer.

2. The back-contact solar cell according to claim 1, characterized in that, The composite metal conductive layer is disposed on the transparent conductive layer.

3. The back-contact solar cell according to claim 1, characterized in that, The back side of the battery cell substrate has alternately arranged N-type conductive regions and P-type conductive regions. The transparent conductive layer and the composite conductive layer are stacked on the N-type conductive regions and P-type conductive regions and separated by an isolation groove. The isolation groove is achieved by etching the composite conductive layer and the transparent conductive layer. The ratio of the width of the composite conductive layer to the width of the isolation groove is 3:1 to 10:

1.

4. The back-contact solar cell according to claim 1, characterized in that, The first conductive layer is made of copper, tin, or silver; when the first conductive layer is tin or silver, the second conductive layer is not provided. The material of the second conductive layer includes at least one of tin, silver, and nickel; or, the second conductive metal layer is one of an indium oxide film, a doped tin oxide film, or a doped zinc oxide film.

5. The back-contact solar cell according to claim 1, characterized in that, The thickness of the transparent conductive layer is 10 nm to 200 nm; the thickness of the composite metal layer is 70 nm to 550 nm; the thickness of the first conductive layer is 50 nm to 450 nm; and the thickness of the second conductive layer is 20 nm to 100 nm. And / or, the material of the transparent conductive layer includes at least one of a doped indium oxide film, a tungsten-doped indium oxide film, a doped tin oxide film, or a doped zinc oxide film.

6. The back-contact solar cell according to claim 1, characterized in that, The material of the fine grid electrode includes low-temperature silver paste or silver-copper paste; or, the fine grid electrode is an electroplated copper grid metal electrode. The main grid electrode is made of low-temperature silver paste or silver-copper paste.

7. The back-contact solar cell according to claim 1, characterized in that, The insulating layer is made of insulating adhesive; and / or the thickness of the insulating layer is 5 μm to 50 μm.

8. A method for fabricating a back-contact solar cell, configured to fabricate a back-contact solar cell as described in any one of claims 1 to 7, characterized in that, include: Provide a solar cell substrate; The back side of the battery cell substrate has alternately arranged N-type conductive regions and P-type conductive regions. A transparent conductive film layer and a composite conductive film layer are sequentially prepared on the back side of the battery cell substrate; The transparent conductive film layer and the composite conductive film layer located at the junction of the N-type conductive region and the P-type conductive region are removed by a patterning process, thereby forming an isolation groove and the transparent conductive layer and the composite conductive layer stacked in the N-type conductive region and the P-type conductive region; Fine grid electrodes, insulating layers, and main grid electrodes are sequentially fabricated on a solar cell substrate with isolation grooves.

9. The method for fabricating a back-contact solar cell according to claim 8, characterized in that, The step of sequentially fabricating a fine grid electrode, an insulating layer, and a main grid electrode on a solar cell substrate having the isolation trench includes: The fine gate electrode of the low-temperature silver paste material is fabricated by screen printing or pad printing, or by electroplating copper fine gate. When the polarity of the main gate electrode and the fine gate electrode are the same, the fine gate electrode remains continuous. When the polarity of the main gate electrode and the fine gate electrode are different, the fine gate electrode is pre-broken in the area overlapping with the main gate electrode, and the break length of the fine gate electrode is 0.1 mm to 10 mm. An insulating layer is fabricated in the area where the fine gate electrode is broken using screen printing, pad printing, or inkjet printing. The dimension of the insulating layer along the second direction is 1.1 to 1.5 times the length of the break in the fine gate electrode; the dimension of the insulating layer along the first direction is 1.1 to 1.5 times the width of the composite conductive layer. The main gate electrode is fabricated on the insulating layer using screen printing or pad printing. The main gate electrode covers the insulating layer and is connected to the fine gate electrode of the same polarity.

10. A method for fabricating a back-contact solar cell, configured to fabricate a back-contact solar cell as described in any one of claims 1 to 7, characterized in that, include: Provide a solar cell substrate; The back side of the battery cell substrate has alternately arranged N-type conductive regions and P-type conductive regions. A transparent conductive film layer and a composite conductive film layer are sequentially prepared on the back side of the battery cell substrate; An isolation trench is fabricated on the back of the battery cell substrate at the junction of the N-type conductive region and the P-type conductive region using a patterning process, so as to form a transparent conductive layer and a composite conductive layer separated by the isolation trench. Fine grid electrodes and an insulating layer are sequentially fabricated on a battery substrate with pre-fabricated isolation trenches; The main gate electrode is fabricated along a direction perpendicular to the fine gate electrode.

11. A battery assembly, characterized in that, It includes a back-contact solar cell as described in any one of claims 1 to 7.

Images