Topcon cell and method of manufacturing the same

Abstract

The application belongs to the technical field of solar cells, and particularly relates to a ToPCon cell and a preparation method thereof. The preparation method of the ToPCon cell comprises the following steps: performing texturing on the front surface of a substrate; performing boron diffusion treatment on the front surface of the texturing substrate; removing a borosilicate glass layer plated around the back surface of the substrate; sequentially depositing a tunneling oxide layer and a polysilicon layer on the back surface of the substrate; sequentially removing a phosphosilicate glass layer, a polysilicon layer and a tunneling oxide layer plated around the front surface of the substrate; and removing the borosilicate glass layer on the front surface of the substrate through alkali texturing treatment. In the process of removing the borosilicate glass layer through alkali texturing treatment, the problem that the second textured surface on the front surface of the substrate is damaged by the alkaline solution does not need to be considered, so that the problem that the borosilicate glass layer cannot be completely removed and the performance of the cell is reduced can be solved, that is, the preparation method of the application can completely remove the borosilicate glass layer without damaging the textured surface of the substrate.

Description

Technical Field

[0001] This application belongs to the field of solar cell technology, specifically relating to a ToPCon cell and its fabrication method. Background Technology

[0002] The core of fabricating TOPCon (Tunnel Oxide Passivated Contact) solar cells is to fabricate the tunnel oxide layer and polycrystalline silicon layer on the back side of the substrate. During the deposition of the tunnel oxide layer and polycrystalline silicon layer on the back side of the substrate, the tunnel oxide layer and polycrystalline silicon layer are deposited around the front side of the substrate, thereby covering the borosilicate glass layer on the front side of the substrate. The passivation antireflection film on the front side of the substrate needs to be deposited on the textured surface covered by the borosilicate glass layer. Therefore, before depositing the passivation antireflection film on the front side of the substrate, the polycrystalline silicon layer, tunnel oxide layer and borosilicate glass layer deposited around the front side of the substrate need to be removed.

[0003] In this field, alkaline polishing in a tank is commonly used to remove the polycrystalline silicon layer, tunnel oxide layer, and borosilicate glass layer. However, alkaline polishing in a tank can lead to over-polishing and under-polishing. Over-polishing refers to the alkaline polishing solution further polishing the front side of the substrate after polishing the borosilicate glass layer, which can damage the textured surface of the substrate. Under-polishing refers to the failure to completely remove the borosilicate glass layer, which can reduce the performance of the battery. Summary of the Invention

[0004] The purpose of this application is to provide a ToPCon battery and its preparation method, which can solve the problems of over-polishing and under-polishing that exist when using the current method of trough alkaline polishing to remove the borosilicate glass layer.

[0005] To solve the above-mentioned technical problems, this application is implemented as follows:

[0006] In a first aspect, embodiments of this application provide a method for preparing a ToPCon battery, comprising:

[0007] Texturing is performed on the front side of the substrate;

[0008] Boron diffusion treatment is performed on the front side of the texturized substrate;

[0009] Remove the borosilicate glass layer coated around the back of the substrate;

[0010] A tunneling oxide layer and a polycrystalline silicon layer are deposited sequentially on the back side of the substrate;

[0011] The phosphorosilicate glass layer, polycrystalline silicon layer, and tunneling oxide layer deposited around the front side of the substrate are removed sequentially.

[0012] The borosilicate glass layer on the front side of the substrate is removed by alkaline texturing.

[0013] Secondly, embodiments of this application also provide a ToPCon battery, which is prepared by the above-described preparation method.

[0014] In this embodiment, after boron diffusion treatment is performed on the front side of the textured substrate, a borosilicate glass layer is formed on the front side of the substrate. The borosilicate glass layer is deposited around the sides and back of the substrate. After removing the borosilicate glass layer on the back of the substrate, a tunneling oxide layer and a polysilicon layer can be deposited. During this process, the tunneling oxide layer, polysilicon layer, and phosphosilicate glass layer are deposited around the sides and front of the substrate. After removing the phosphosilicate glass layer, polysilicon layer, and tunneling oxide layer deposited around the front of the substrate, this embodiment removes the borosilicate glass layer on the front of the substrate through alkaline texturing. When the alkaline solution used in the alkaline texturing process comes into contact with the front of the substrate, it will texture the substrate without polishing it, thus avoiding damage to the second textured surface on the front of the substrate. As can be seen, in the process of removing the borosilicate glass layer by alkaline texturing in the embodiments of this application, there is no need to consider the problem of alkaline solution damaging the second textured surface of the substrate. This solves the problem of incomplete removal of the borosilicate glass layer and reduced battery performance. In other words, the preparation method of the embodiments of this application can completely remove the borosilicate glass layer without damaging the textured surface of the substrate. Attached Figure Description

[0015] Figure 1 This is a schematic flowchart of the ToPCon battery fabrication method disclosed in the embodiments of this application;

[0016] Figure 2 This is a schematic flowchart of a method for preparing a ToPCon battery according to another embodiment of this application;

[0017] Figure 3 This is a schematic diagram of the ToPCon battery structure disclosed in the embodiments of this application.

[0018] Explanation of reference numerals in the attached figures:

[0019] 100 - Substrate, 110 - First textured surface, 120 - Second textured surface, 200 - Tunneling oxide layer, 300 - Polycrystalline silicon layer, 400 - Passivation antireflection film, 500 - Electrode. Detailed Implementation

[0020] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0021] The terms "first," "second," etc., used in the specification and claims of this application are used to distinguish similar objects and not to describe a specific order or sequence. It should be understood that such use of data can be interchanged where appropriate so that embodiments of this application can be implemented in orders other than those illustrated or described herein, and the objects distinguished by "first," "second," etc., are generally of the same class and the number of objects is not limited; for example, a first object can be one or more. Furthermore, in the specification and claims, "and / or" indicates at least one of the connected objects, and the character " / " generally indicates that the preceding and following objects are in an "or" relationship.

[0022] The ToPCon battery and its preparation method provided in this application will be described in detail below with reference to the accompanying drawings and through specific embodiments and application scenarios.

[0023] like Figures 1 to 2 As shown in the embodiments of this application, a method for fabricating a ToPCon battery is disclosed, comprising:

[0024] S100: Texturing is performed on the front side of the substrate 100.

[0025] The substrate 100 can be a silicon wafer. During texturing, an N-type silicon substrate can be selected, and single-crystal alkaline texturing is performed in a tank mill to form a pyramid-shaped second textured surface 120 on the front side of the substrate 100. The size of the second textured surface 120 is controlled between 1 and 5 μm. Here, the size of the second textured surface 120 refers to the width of the base of the pyramid. The weight reduction of the substrate 100 is controlled between 0.25 and 0.5 g, and the reflectivity of the front side of the substrate 100 is controlled within 11%.

[0026] S200, perform boron diffusion treatment on the front side of the texturized substrate 100.

[0027] The second textured surface 120 on the front side of the substrate 100 is subjected to boron diffusion treatment. Boron trichloride is used for multi-step diffusion at high temperature to form a P-type doped layer on the front side of the substrate 100. The diffusion temperature of the boron diffusion treatment is 900-1100℃, the diffusion time is 2-3h, the sheet resistance of the P-type doped layer is 100-200 ohm·cm, and the thickness of the borosilicate glass layer generated during the boron diffusion treatment is 50-100nm.

[0028] S300, Remove the borosilicate glass layer coated on the back of the substrate 100.

[0029] During the boron diffusion process, a borosilicate glass layer is formed on the front side of the substrate 100. The borosilicate glass layer is deposited around the sides and back of the substrate 100. The borosilicate glass layer deposited around the back of the substrate 100 can be removed using a hydrofluoric acid solution. Further, after removing the borosilicate glass layer deposited around the back of the substrate 100, an alkaline etchant can be used to remove the P-type doped layer deposited around the back of the substrate 100 to control the reflectivity of the back of the substrate 100 to 35%–45%, and to control the size of the blocky base on the back of the substrate 100 to between 7 and 15 μm. Here, the blocky base refers to the blocky pillars formed on the back of the substrate 100, the size of which is the width of the bottom of the blocky base.

[0030] S400, a tunneling oxide layer 200 and a polysilicon layer 300 are sequentially deposited on the back side of the substrate 100.

[0031] A tunneling oxide layer 200 and an intrinsic amorphous silicon layer (a-Si) can be sequentially deposited on the back side of the substrate 100 using LPCVD (Low-pressure CVD) technology. Then, the intrinsic amorphous silicon layer is subjected to phosphorus diffusion treatment to form a polycrystalline silicon layer 300. The thickness of the deposited tunneling oxide layer 200 is 1-2 nm, the thickness of the intrinsic amorphous silicon layer is 60-150 nm, and the sheet resistance of the polycrystalline silicon layer 300 is 40-120 ohm·cm.

[0032] S500, sequentially remove the phosphorus silicate glass layer, polysilicon layer 300 and tunneling oxide layer 200 deposited on the front side of the substrate 100.

[0033] During the phosphorus diffusion process of the intrinsic amorphous silicon layer, a phosphosilicate glass layer is formed on its back side. The deposited tunneling oxide layer 200, polycrystalline silicon layer 300, and phosphosilicate glass layer are sequentially deposited around the borosilicate glass layers on the front and side surfaces of the substrate 100. Before depositing the passivation antireflection film 400 on the front surface of the substrate 100, the tunneling oxide layer 200, polycrystalline silicon layer 300, and borosilicate glass layer deposited around the front surface of the substrate 100 need to be removed.

[0034] S600, the borosilicate glass layer on the front side of the substrate 100 is removed by alkaline texturing treatment.

[0035] In this embodiment, after boron diffusion treatment is performed on the front side of the textured substrate 100, a borosilicate glass layer is formed on the front side of the substrate 100. The borosilicate glass layer is deposited around the sides and back of the substrate 100. After removing the borosilicate glass layer on the back of the substrate 100, a tunneling oxide layer 200 and a polysilicon layer 300 can be deposited. During this process, the tunneling oxide layer 200, the polysilicon layer 300, and the phosphosilicate glass layer are deposited around the sides and front of the substrate 100. After removing the phosphosilicate glass layer, the polysilicon layer 300, and the tunneling oxide layer 200 deposited around the front of the substrate 100, this embodiment removes the borosilicate glass layer on the front of the substrate 100 by alkaline texturing. When the alkaline solution used in the alkaline texturing comes into contact with the front of the substrate 100, it will texture the substrate 100 without polishing it. Therefore, the second textured surface 120 on the front of the substrate 100 will not be damaged. As can be seen, in the process of removing the borosilicate glass layer by alkaline texturing in the embodiments of this application, there is no need to consider the problem of alkaline solution damaging the second textured surface 120 on the front side of the substrate 100. This solves the problem of the inability to completely remove the borosilicate glass layer and reduce battery performance. In other words, the preparation method of the embodiments of this application can completely remove the borosilicate glass layer without damaging the second textured surface 120 of the substrate 100.

[0036] In an optional embodiment, prior to step S600, the method further includes:

[0037] S700, sequentially remove the phosphorus silicate glass layer, polysilicon layer 300 and tunneling oxide layer 200 deposited around the side of the substrate 100.

[0038] Step S600 is as follows:

[0039] S610, The borosilicate glass layer on the front side of the substrate 100 is removed by alkaline texturing treatment, and a first textured surface 110 is formed on the side side of the substrate 100.

[0040] In this embodiment, while removing the borosilicate glass layer on the front side of the substrate 100, the alkaline solution for alkaline texturing can be brought into contact with the side surface of the substrate 100, thereby forming a first textured surface 110 on the side surface of the substrate 100. The pyramidal structure of the first textured surface 110 can better isolate the PN junction, thereby improving the problem of edge leakage in the ToPCon battery. At the same time, the first textured surface 110 on the side surface of the substrate 100 can also increase the light absorption of the ToPCon battery, thereby improving battery efficiency. It can be seen that the alkaline texturing process can not only completely remove the borosilicate glass layer without damaging the second textured surface 120, but also form the first textured surface 110 on the side surface of the substrate 100, thereby preventing edge leakage in the ToPCon battery and improving battery efficiency. In other words, the alkaline texturing process in this embodiment can achieve multiple effects.

[0041] In an optional embodiment, step S610 specifically involves:

[0042] S611. The borosilicate glass layer on the front and side surfaces of the substrate 100 is removed by alkaline texturing treatment, and a first textured surface 110 is formed on the side surface of the substrate 100.

[0043] Specifically, step S500 can be as follows: sequentially removing the phosphosilicate glass layer, polysilicon layer 300, and tunneling oxide layer 200 deposited on the front and side surfaces of the substrate 100; at this time, step S510 below specifically involves: using hydrofluoric acid solution to remove the phosphosilicate glass layer deposited on the front and side surfaces of the substrate 100; step S520 below specifically involves: using alkaline etching treatment to remove the polysilicon layer 300 and tunneling oxide layer 200 deposited on the front and side surfaces of the substrate 100. After removing the phosphosilicate glass layer, polysilicon layer 300, and tunneling oxide layer 200 from the side of substrate 100, a borosilicate glass layer still exists on the side of substrate 100. In this embodiment, the borosilicate glass layer and P-type doped layer deposited on the side of substrate 100 are removed by alkaline texturing. That is, the alkaline texturing removes the borosilicate glass layer on the front of substrate 100 and the borosilicate glass layer and P-type doped layer on the side of substrate 100 at the same time. Thus, there is no need to add an extra process to remove the borosilicate glass layer and P-type doped layer on the side of substrate 100, thereby saving process steps.

[0044] In one optional embodiment, the alkaline solution used for alkaline texturing has an alkali mass fraction of 0.5% to 2%. If the alkali mass fraction of the alkaline solution is less than 0.5%, it may not be possible to completely remove the borosilicate glass layer on the front side of the substrate 100, and it may not be possible to form the first textured surface 110 on the side of the substrate 100. If the alkali mass fraction of the alkaline solution is greater than 2%, the second textured surface 120 may be damaged after the alkaline solution comes into contact with the second textured surface 120 on the front side of the substrate 100. Therefore, in this embodiment, the alkali mass fraction of the alkaline solution is controlled at 0.5% to 2%, which allows for the complete removal of the borosilicate glass layer on the front side of the substrate 100 and the formation of the first textured surface 110 on the side of the substrate 100 without damaging the second textured surface 120. Furthermore, the alkaline solution used in the alkali texturing process also includes additives, the volume fraction of which is controlled at 0.5% to 2%. This allows the borosilicate glass layer on the front side of the substrate 100 to be completely removed, and the first texturing surface 110 to be formed on the side side of the substrate 100, without damaging the second texturing surface 120.

[0045] In one optional embodiment, the alkaline texturing process takes 50–200 seconds and is carried out at a temperature of 60–75°C. If the alkaline texturing process takes less than 50 seconds, the borosilicate glass layer on the front side of the substrate 100 may not be completely removed, and the first textured surface 110 may not be formed on the side of the substrate 100. If the alkaline texturing process takes more than 200 seconds, the contact time between the alkaline solution and the second textured surface 120 may be too long, potentially damaging the second textured surface 120. Therefore, this embodiment controls the alkaline texturing process to 50–200 seconds, ensuring that the borosilicate glass layer on the front side of the substrate 100 is completely removed and the first textured surface 110 is formed on the side of the substrate 100 without damaging the second textured surface 120. Similarly, in this embodiment, the alkaline texturing treatment temperature is controlled at 60-75°C, which can completely remove the borosilicate glass layer on the front side of the substrate 100 and form the first texturing surface 110 on the side side of the substrate 100 without damaging the second texturing surface 120.

[0046] In one optional embodiment, the preparation method further includes:

[0047] S800. The surface of the substrate 100 after alkaline texturing is cleaned using a mixed acid solution. Optionally, the mixed acid solution can be a mixture of hydrochloric acid and hydrofluoric acid. It should be noted that when step S610 is specifically step S611, the mixed acid solution can clean both the front and sides of the substrate 100.

[0048] After removing the borosilicate glass layer on the front side of the substrate 100 through alkaline texturing, alkaline liquid and particulate matter remain on the front side of the substrate 100, which is detrimental to the subsequent deposition of the passivation antireflection film 400. In this embodiment, a mixed acid solution is used to clean the surface of the substrate 100 after alkaline texturing. The mixed acid solution can not only remove particulate matter on the substrate 100, but also neutralize the alkaline liquid remaining on the substrate 100, thereby facilitating the deposition of the passivation antireflection film 400. Furthermore, the surface of the substrate 100 after cleaning with the mixed acid solution is dried, which can shorten the fabrication time of the TOPCon cell. Optionally, before step S800, the surface of the substrate 100 after alkaline texturing can be pre-cleaned by sequentially washing with water and ozone.

[0049] In an optional embodiment, step S500 specifically includes:

[0050] S510. Use hydrofluoric acid solution to remove the phosphosilicate glass layer coated on the front side of the substrate 100.

[0051] S520, use alkaline etching to remove the polysilicon layer 300 and tunnel oxide layer 200 deposited around the front side of the substrate 100.

[0052] The alkaline etching solution used in the alkaline etching process has an alkali mass fraction of 0.5% to 5%, the alkaline etching time is 50 to 100 seconds, and the processing temperature is 50 to 60°C.

[0053] In this embodiment, if the alkali mass fraction of the alkaline etching solution is less than 0.5%, the polysilicon layer 300 and the tunneling oxide layer 200 cannot be completely removed, which is detrimental to the removal of the borosilicate glass layer by alkaline texturing. If the alkali mass fraction of the alkaline etching solution is greater than 5%, the alkaline etching solution may remove the borosilicate glass layer and come into contact with the second textured surface 120 on the front side of the substrate 100, thereby damaging the second textured surface 120. In this embodiment, the alkali mass fraction of the alkaline etching solution is controlled between 0.5% and 5%, which allows the alkaline etching solution to completely remove the polysilicon layer 300 and the tunneling oxide layer 200 without damaging the second textured surface 120. Similarly, by controlling the alkaline etching process time to 50-100 seconds and the processing temperature to 50-60°C, the alkaline etching solution can completely remove the polysilicon layer 300 and the tunneling oxide layer 200 without damaging the second textured surface 120.

[0054] In one optional embodiment, the preparation method further includes:

[0055] S910, passivation antireflection films 400 are deposited on the front and back sides of the substrate 100, respectively.

[0056] The passivation antireflection film 400 can be a dielectric layer composed of one or more of AlOx, SiNx, SiOxNy, and SiOx layers, i.e., a single AlOx, SiNx, SiOxNy, or SiOx layer, or a multilayer dielectric film composed of two or more of AlOx, SiNx, SiOxNy, and SiOx layers. If it is a multilayer film, the deposition order is not important. AlOx can be Al2O3.

[0057] S920, electrodes 500 are fabricated on the front and back sides of the substrate 100, respectively.

[0058] This step involves metallizing both the front and back sides of the substrate 100. Silver paste electrodes 500 can be printed sequentially on the back side of the substrate 100 and silver-aluminum paste electrodes 500 on the front side of the substrate 100 using screen printing. Then, the solar cell is fabricated by sintering.

[0059] like Figure 3 As shown in the embodiments, this application also discloses a ToPCon battery, which is prepared by the preparation method described in any of the above embodiments.

[0060] In one alternative embodiment, the side surface of the substrate 100 has a first textured surface 110.

[0061] In this embodiment, the pyramidal structure of the first textured surface 110 can better isolate the PN junction, thereby improving the problem of leakage at the edge of the ToPCon battery; at the same time, the first textured surface 110 on the side of the substrate 100 can also increase the absorption of light by the ToPCon battery, thereby improving the battery efficiency.

[0062] The foregoing embodiments of this application focus on describing the differences between various embodiments. As long as the different optimization features between embodiments are not contradictory, they can be combined to form better embodiments. For the sake of brevity, these differences will not be elaborated upon here. The embodiments of this application have been described above with reference to the accompanying drawings. However, this application is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art, under the guidance of this application, can make many modifications without departing from the spirit and scope of the claims, all of which fall within the protection scope of this application.

Claims

1. A method for preparing a ToPCon battery, characterized in that, include: The front side of the substrate (100) is textured to form a second textured surface (120). Boron diffusion treatment was performed on the front side of the texturized substrate (100); Remove the borosilicate glass layer coated around the back of the substrate (100); A tunneling oxide layer (200) and a polysilicon layer (300) are sequentially deposited on the back side of the substrate (100). The phosphorosilicate glass layer, polysilicon layer (300) and tunnel oxide layer (200) coated on the front side of the substrate (100) are removed in sequence. The borosilicate glass layer on the front side of the substrate (100) is removed by alkaline texturing without damaging the second textured surface (120). The alkaline solution used in the alkaline texturing treatment has an alkali mass fraction of 0.5% to 2%, the treatment time is 50 to 200 seconds, and the treatment temperature is 60 to 75°C.

2. The preparation method according to claim 1, characterized in that, Prior to the step of removing the borosilicate glass layer on the front side of the substrate (100) by alkaline texturing, the method further includes: The phosphorosilicate glass layer, polysilicon layer (300) and tunneling oxide layer (200) deposited around the side of the substrate (100) are removed in sequence. The removal of the borosilicate glass layer on the front side of the substrate (100) by alkaline texturing specifically involves: The borosilicate glass layer on the front side of the substrate (100) is removed by alkaline texturing, and a first textured surface (110) is formed on the side side of the substrate (100).

3. The preparation method according to claim 2, characterized in that, The step of removing the borosilicate glass layer on the front side of the substrate (100) by alkaline texturing and forming a first textured surface (110) on the side side of the substrate (100) specifically involves: The borosilicate glass layer on the front and side surfaces of the substrate (100) is removed by alkaline texturing, and a first textured surface (110) is formed on the side surface of the substrate (100).

4. The preparation method according to claim 1, characterized in that, The preparation method further includes: The surface of the substrate (100) after alkali texturing was cleaned using a mixed acid solution.

5. The preparation method according to claim 1, characterized in that, The step of sequentially removing the phosphosilicate glass layer, polycrystalline silicon layer (300), and tunneling oxide layer (200) deposited around the front side of the substrate (100) specifically includes: The phosphosilicate glass layer coated on the front side of the substrate (100) was removed using a hydrofluoric acid solution. The polysilicon layer (300) and tunnel oxide layer (200) coated around the front side of the substrate (100) are removed by alkaline etching. The alkaline etching solution used in the alkaline etching process has an alkaline mass fraction of 0.5% to 5%, the alkaline etching time is 50 to 100 seconds, and the processing temperature is 50 to 60°C.

6. The preparation method according to claim 1, characterized in that, The preparation method further includes: Passivation antireflection films (400) are deposited on the front and back sides of the substrate (100), respectively. Electrodes (500) are fabricated on the front and back sides of the substrate (100), respectively.

7. A ToPCon battery, characterized in that, Prepared by the preparation method according to any one of claims 1 to 6.

8. The ToPCon battery according to claim 7, characterized in that, The side of the substrate (100) has a first textured surface (110).

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