Preparation method of TOPcon battery, TOPcon battery and battery assembly

Abstract

The present invention relates to the field of battery technology, and specifically provides a method for preparing a TOPcon battery, a TOPcon battery and a battery assembly, aiming to solve the problem of low conversion efficiency of TOPcon batteries prepared by PECVD process in the prior art. To this end, the method for preparing a TOPcon battery of the present invention comprises the following steps: S1: forming a tower base structure on the back of a substrate; S2: forming an oxide layer on the tower base structure; S3: forming a tunneling oxide layer on the oxide layer by PECVD. By first forming an oxide layer on the tower base structure, and then forming a tunneling oxide layer on the oxide layer by PECVD process, the film formation uniformity of the tunneling oxide layer can be improved by the oxide layer formed on the tower base structure. In this way, the PECVD process is used to prepare a TOPcon battery, which can not only form a film quickly, but also greatly improve the film formation quality, thereby improving the conversion efficiency of the TOPcon battery, which helps to improve the performance of the TOPcon battery.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and specifically provides a method for preparing a TOPcon battery, a TOPcon battery and a battery assembly. Background Art

[0002] TOPCon (TOPCon stands for Tunnel Oxide Passivating Contacts, which is an N-type silicon wafer battery technology proposed in 2013) batteries have attracted attention in the photovoltaic industry as a battery that is closest to the theoretical efficiency value of crystalline silicon batteries.

[0003] At present, the preparation of TOPCon cells in the market mainly uses the LPCVD process (low-pressure chemical vapor deposition), which is mature, simple to control, has high film density and high safety. It is the most mature technical route and has achieved large-scale mass production. However, the deposition rate of the LPCVD process is low, and there are problems such as difficulty in winding plating and in-situ doping.

[0004] The PECVD process has the characteristics of low operating temperature, fast film formation speed, and is not picky about materials. It also has an in-situ monitoring system and is suitable for large-scale production and for applications that require rapid deposition. However, the conversion efficiency of TOPcon cells prepared using the PECVD process is extremely low and the battery performance is poor. Summary of the invention

[0005] The present invention aims to solve the above technical problems at least to a certain extent, that is, to solve the problem of low conversion efficiency of TOPcon cells prepared by PECVD process in the prior art at least to a certain extent.

[0006] In a first aspect, the present invention provides a method for preparing a TOPcon battery, the preparation method comprising the following steps: S1: forming a tower base structure on the back side of a substrate; S2: forming an oxide layer on the tower base structure; S3: forming a tunneling oxide layer on the oxide layer using a PECVD process.

[0007] In the preferred technical scheme of the preparation method of the above-mentioned TOPcon battery, the step of "forming an oxide layer on the tower base structure" specifically includes: performing post-cleaning and acid washing treatments on the battery structure after the tower base structure is formed in sequence to form the oxide layer, wherein the post-cleaning liquid of the post-cleaning treatment includes at least hydrogen peroxide, and the acid washing liquid of the acid washing treatment does not contain HF.

[0008] In the preferred technical solution of the above-mentioned TOPcon battery preparation method, the lateral size of the tower base structure is 9 μm-13 μm, the flatness of the tower base structure is 0.20-0.25, and the thickness of the tunneling oxide layer is 1.5 nm-2.0 nm.

[0009] In the preferred technical solution of the above-mentioned method for preparing the TOPcon battery, the thickness of the oxide layer is 1.4nm-1.8nm.

[0010] In the preferred technical solution of the above-mentioned method for preparing the TOPcon battery, the step of "forming a tower base structure on the back side of the substrate" specifically includes: performing an alkaline washing treatment on the back side of the substrate to form the tower base structure.

[0011] In the preferred technical solution of the above-mentioned method for preparing TOPcon battery, the time range of the alkaline washing treatment is 220s-240s, and the temperature range is 62-64°C.

[0012] In a second aspect, the present invention also provides a TOPcon battery, comprising: a substrate having a tower base structure on the back side; an oxide layer disposed on the tower base structure; and a tunneling oxide layer disposed on the oxide layer, wherein the tunneling oxide layer is manufactured using a PECVD process.

[0013] In the preferred technical solution of the above-mentioned TOPcon battery, the lateral dimension of the tower base structure is 9 μm-13 μm, the flatness of the tower base structure is 0.20-0.25, and the thickness of the tunneling oxide layer is 1.5 nm-2.0 nm.

[0014] In the preferred technical solution of the above-mentioned TOPcon cell, the TOPcon cell also includes: a back anti-reflection layer and a back electrode stacked in sequence on the tunneling oxide layer; a diffusion layer, a passivation layer, a front anti-reflection layer and a front electrode stacked in sequence on the front side of the substrate.

[0015] In a third aspect, the present invention further provides a battery assembly, which includes the TOPcon battery described in any one of the above-mentioned items.

[0016] When the above-mentioned preferred technical scheme is adopted, by first forming an oxide layer on the tower base structure, and then using the PECVD process to form a tunnel oxide layer on the oxide layer, the film formation quality and uniformity of the tunnel oxide layer can be improved through the oxide layer formed on the tower base structure, and the passivation effect of the tunnel oxide layer can be improved. In this way, when the PECVD process is used to prepare TOPcon batteries, not only can the film be formed quickly, but also the film formation quality can be greatly improved, thereby improving the preparation efficiency and conversion efficiency of the TOPcon batteries, and solving the problem of poor performance of the prepared TOPcon batteries due to poor film formation uniformity and quality when the PECVD process is used to prepare TOPcon batteries in the prior art.

[0017] Furthermore, an oxide layer is formed by sequentially performing post-cleaning and pickling treatments on the battery structure after the tower base structure is formed, and the post-cleaning liquid of the post-cleaning treatment is set to include hydrogen peroxide, and the pickling liquid of the pickling treatment is set to be HF-free. On the one hand, it is possible to avoid the HF in the pickling liquid from reacting with the oxide layer formed on the tower base structure, thereby forming an oxide layer on the tower base structure, and then the oxide layer can be used to improve the film formation uniformity of the tunneling oxide layer subsequently formed by the PECVD process, which helps to improve the performance of the TOPcon battery; on the other hand, since the pickling liquid does not contain HF, it is also possible to avoid HF corrosion to the equipment and the environment, reduce the production cost of the TOPcon battery, and improve the safety of the TOPcon battery during the preparation process.

[0018] Furthermore, by controlling the thickness of the oxide layer to 1.4nm-1.8nm, it is possible to avoid the oxide layer being too thick, which would result in the total thickness of the oxide layer and the tunnel oxide layer being too large, thereby avoiding the inactivation of phosphorus atoms. On the other hand, it is also possible to avoid the inability to clean the dirt and additives remaining on the surface of the substrate during post-cleaning due to the small thickness of the oxide layer, thereby affecting the performance of the battery.

[0019] Furthermore, by setting the lateral dimension of the tower base structure 51 to 9-13μm, the flatness of the tower base structure 51 to 0.20-0.25, and the thickness of the tunneling oxide layer prepared by the PECVD process to 1.5nm-2.0nm, on the one hand, the process matching can be better, so that the tunneling oxide layer and the oxide layer formed on the tower base structure can be coordinated to improve the film formation uniformity and film formation quality, thereby improving the performance of the prepared TOPcon battery; on the other hand, the oxide layer formed on the tower base structure can be filled with the help of the tunneling oxide layer, covering the uneven structural differences on the back side of the substrate, covering the watermark anomalies, and avoiding the presence of water marks affecting the passivation effect.

[0020] In addition, the battery module further provided by the present invention on the basis of the above-mentioned technical solution includes the TOPcon battery introduced above, and thus has the beneficial effects of the above-mentioned TOPcon battery. Compared with the battery module before the improvement, the battery module of the present invention has better electrical performance and higher photoelectric conversion rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The preferred embodiments of the present invention are described below in conjunction with the accompanying drawings, in which:

[0022] Figure 1 It is a schematic diagram of the structure of the TOPcon battery of the present invention;

[0023] Figure 2 is a scanning electron microscope image of the tower base structure on the back side of the substrate of the present invention;

[0024] Figure 3 is a flow chart of a method for preparing a TOPcon battery of the present invention;

[0025] Figure 4 EL performance diagram of TOPcon cells prepared in Examples 1 to 3;

[0026] Figure 5 These are EL performance graphs of the TOPcon cells prepared in Comparative Examples 1 to 3.

[0027] List of reference numerals:

[0028] 1. Front electrode; 2. Front anti-reflection layer; 3. Passivation layer; 4. Diffusion layer; 5. Substrate; 51. Tower base structure; 6. Oxide layer; 7. Tunneling oxide layer; 8. Polysilicon (poly) layer; 9. Back anti-reflection layer; 10. Back electrode. DETAILED DESCRIPTION

[0029] The preferred embodiments of the present invention are described below with reference to the accompanying drawings. It should be understood by those skilled in the art that these embodiments are only used to explain the technical principles of the present invention and are not intended to limit the protection scope of the present invention.

[0030] Unless otherwise specified, the terms used in this application have the commonly known meanings generally understood by those skilled in the art. Unless otherwise specified, the numerical values ​​of the various parameters mentioned in this application can be measured using various measurement methods commonly used in the art (for example, they can be tested according to the methods given in the examples of this application).

[0031] The experimental methods in the following examples are conventional methods unless otherwise specified; the raw materials, reagents, etc. used in the following examples are commercially available products unless otherwise specified.

[0032] A list of items connected by the term "at least one of" or other similar terms may mean any combination of the listed items. For example, if items A and B are listed, the phrase "at least one of A and B" means only A; only B; or A and B. In another example, if items A, B, and C are listed, the phrase "at least one of A, B, and C" means only A; or only B; only C; A and B (excluding C); A and C (excluding B); B and C (excluding A); or all of A, B, and C. Item A may contain a single component or multiple components. Item B may contain a single component or multiple components. Item C may contain a single component or multiple components.

[0033] The present application is further described below in conjunction with specific implementations. It should be understood that these specific implementations are only used to illustrate the present application and are not used to limit the scope of the present application.

[0034] Based on the problem of low conversion efficiency of the existing TOPcon battery prepared by PECVD process mentioned in the background technology, the inventors have found that the reason for the low conversion efficiency of the TOPcon battery prepared by PECVD process is that the tunneling oxide layer formed by the PECVD process has poor uniformity, and the poor uniformity will affect the passivation efficiency of the tunneling oxide layer, thereby making the conversion efficiency of the prepared TOPcon battery low. Based on this, the present invention provides a method for preparing a TOPcon battery.

[0035] Specifically, see Figures 1 to 3 , Figure 1 is a schematic structural diagram of the TOPcon battery of the present invention, Figure 2 is a scanning electron microscope image of the tower base structure on the back side of the substrate of the present invention, Figure 3 It is a flow chart of the method for preparing the TOPcon battery of the present invention.

[0036] like Figures 1 to 3 As shown, the preparation method of the TOPcon battery of the present invention comprises the following steps:

[0037] S1: forming a tower base structure 51 on the back side of the substrate 5;

[0038] S2: forming an oxide layer 6 on the tower base structure 51;

[0039] S3: forming a tunnel oxide layer 7 on the oxide layer 6 by using a PECVD process.

[0040] With such a setting, although the tunneling oxide layer 7 formed by the PECVD process can form a film quickly, the film formation uniformity is poor. By first forming an oxide layer 6 on the tower base structure 51 and then forming the tunneling oxide layer 7 on the oxide layer 6 by the PECVD process, the oxide layer 6 and the tunneling oxide layer 7 formed by the PECVD process can jointly play the role of the tunneling oxide layer, and then the oxide layer 6 formed on the tower base structure 51 can improve the film formation uniformity of the tunneling oxide layer 7 formed by the PECVD process, and improve the passivation effect of the tunneling oxide layer 7. In this way, when the PECVD process is used to prepare the TOPcon battery, not only can the film be formed quickly, but also the film formation quality can be greatly improved, thereby improving the conversion efficiency of the TOPcon battery.

[0041] It should be noted that, in practical applications, the present invention does not impose any limitation on the specific formation method of the oxide layer 6. As long as the oxide layer 6 can be formed on the tower base structure 51, such adjustment and change to the specific formation method of the oxide layer 6 does not deviate from the principle and scope of the present invention, and should be included in the protection scope of the present invention.

[0042] In a specific embodiment, the battery structure after forming the tower base structure 51 can be subjected to post-cleaning and pickling treatments in sequence to form an oxide layer 6, wherein the post-cleaning liquid of the post-cleaning treatment includes at least hydrogen peroxide, and the pickling liquid of the pickling treatment does not contain HF.

[0043] In another specific embodiment, the battery structure after the tower base structure 51 is formed may be subjected to post-cleaning and pickling treatments in sequence to form an oxide layer, wherein the post-cleaning liquid of the post-cleaning treatment includes at least hydrogen peroxide, and the pickling liquid of the pickling treatment contains HF, and the formed oxide layer is partially removed by controlling the HF content or the pickling time, and an oxide layer 6 is formed after the local removal.

[0044] In this case, in order to more thoroughly remove the additives on the surface of the silicon wafer, the concentration of hydrogen peroxide in the post-cleaning process needs to be higher or the post-cleaning time needs to be longer, but this will cause the thickness of the generated oxide layer 6 to be too large. In order to avoid the oxide layer 6 being too thick and affecting the passivation effect of the tunneling oxide layer 7, the oxide layer 6 formed by the post-cleaning is partially removed and then the PECVD process is used to form a tunneling oxide layer 7 on the oxide layer 6.

[0045] In another possible embodiment, the battery structure after the tower base structure 51 is formed may be subjected to post-cleaning and pickling treatments in sequence, and then an oxide layer 6 may be generated.

[0046] Preferably, the step of “forming an oxide layer 6 on the tower base structure 51” specifically includes:

[0047] The battery structure after forming the tower base structure 51 is subjected to post-cleaning and pickling treatments in sequence to form an oxide layer 6, wherein the post-cleaning liquid of the post-cleaning treatment at least includes hydrogen peroxide, and the pickling liquid of the pickling treatment does not contain HF.

[0048] Through such an arrangement, the battery structure forming the tower base structure 51 is post-cleaned, and an oxide layer 6 can be formed on the surface of the tower base structure 51 under the action of hydrogen peroxide. The pickling solution of the pickling treatment is set to be HF-free. On the one hand, it is possible to avoid the HF in the pickling solution from reacting with the oxide layer 6 formed on the tower base structure 51, so that the oxide layer 6 on the surface of the tower base structure 51 can be retained, so that the oxide layer 6 can be used to improve the film formation uniformity of the tunneling oxide layer 7 subsequently formed by the PECVD process. At the same time, there is no need to add additional processes to form the oxide layer 6, thereby avoiding increasing the complexity of the process. On the other hand, since the pickling solution does not contain HF, it is also possible to avoid HF corrosion to the equipment and the environment, thereby reducing the production cost of the TOPcon battery and improving the safety of the TOPcon battery during the preparation process.

[0049] It should be noted that, in actual applications, the present invention does not impose any particular limitation on the specific components of the post-cleaning liquid. For example, the post-cleaning liquid may be configured to include only hydrogen peroxide, or the post-cleaning liquid may be configured to be a mixture of hydrogen peroxide and any other possible reagents, etc. Such adjustments and changes to the specific components of the post-cleaning liquid do not deviate from the principle and scope of the present invention, and should be included in the protection scope of the present invention.

[0050] Preferably, the cleaning solution for post-cleaning comprises hydrogen peroxide and sodium hydroxide.

[0051] It should be noted that, in practical applications, the present invention does not impose any particular limitation on the time of post-cleaning. For example, the time of post-cleaning is 60s, 70s, 80s, 90s, 100s, 110s, 120s or a range consisting of any two of these values.

[0052] Preferably, the post-cleaning time is 60s-120s.

[0053] By controlling the post-cleaning time to 60s-120s, the thickness of the oxide layer 6 formed on the tower base structure 51 can be controlled. On the one hand, it can avoid the post-cleaning time being too short, resulting in the inability to clean the additives attached to the substrate 5, thereby avoiding the residual additives affecting the performance of the battery. On the other hand, it can also enable the formed oxide layer 6 to better improve the film formation uniformity of the tunnel oxide layer 6 formed subsequently by the PECVD process, and avoid the oxide layer 6 being too thick and causing the deactivation of phosphorus atoms.

[0054] Preferably, the thickness of the oxide layer 6 is 1.4 nm-1.8 nm.

[0055] By setting the thickness of the oxide layer 6 to 1.4nm-1.8nm, on the one hand, it can avoid the thickness of the oxide layer 6 being too large, which will lead to the total thickness of the oxide layer 6 and the tunnel oxide layer 7 being too large, thereby avoiding the inactivation of phosphorus atoms. On the other hand, it can also avoid the inability to clean the dirt and additives remaining on the surface of the substrate 5 during post-cleaning due to the small thickness of the oxide layer 6, thereby affecting the performance of the battery.

[0056] It should be noted that, in practical applications, the present invention does not impose any particular limitation on the thickness of the oxide layer 6. For example, the thickness of the oxide layer 6 may be set to 1.4 nm, 1.5 nm, 1.6 nm, 1.7 nm, 1.8 nm, or a range consisting of any two of these values.

[0057] The inventors found during the experiment that although HF was eliminated from the pickling solution of the pickling treatment, the oxide layer 6 formed on the tower base structure 51 could be retained, and the oxide layer 6 could improve the uniformity of the tunneling oxide layer 7, effectively improving the conversion efficiency of the TOPcon battery. However, the presence of the oxide layer 6 would cause water marks to appear on the silicon wafer, especially at the position corresponding to the basket teeth.

[0058] After long-term experiments and research by the inventors, it was found that when the substrate is subjected to alkali polishing, it is loaded into a basket and the substrate is in contact with the position of the basket teeth, where water easily remains. Since the oxide layer 6 has good hydrophilicity, water remains in the oxide layer 6 on the back of the substrate at the position corresponding to the basket teeth. After drying, a watermark will be left on the oxide layer 6, so that the thickness of the oxide layer 6 at the watermark is greater than the thickness of the oxide layer 6 at the place without the watermark, which deteriorates the flatness and uniformity of the back of the substrate. At the same time, due to the difference in the structure on the back of the substrate, the refracted light makes the watermark appear in color, showing a water mark, which will affect the passivation effect of the TOPcon battery.

[0059] The inventors have found that by reasonably adjusting the thickness of the tunneling oxide layer 7, not only can the thickness of the tunneling oxide layer 7 be coordinated with the oxide layer 6 formed on the tower base structure 51 to improve the uniformity and quality of film formation, but also the surface of the oxide layer 6 on the back of the substrate 5 can be filled with the help of the tunneling oxide layer 7, covering the uneven structural differences on the back of the substrate 5, and compensating for the thickness differences on the back of the substrate 5 caused by the presence of water marks, thereby covering the watermark anomalies and making the back of the substrate 5 smoother, avoiding the presence of water marks affecting the passivation effect.

[0060] Preferably, the thickness of the tunnel oxide layer 7 is 1.5 nm-2.0 nm.

[0061] It should be noted that the present invention does not impose any particular limitation on the specific thickness of the tunnel oxide layer 7. For example, the thickness of the tunnel oxide layer 7 can be set to 1.5 nm, 1.6 nm, 1.7 nm, 1.8 nm, 1.9 nm, 2.0 nm or a range consisting of any two of these values.

[0062] Preferably, the step of “forming a tower base structure 51 on the back side of the substrate 5” specifically includes:

[0063] S11: The back side of the substrate 5 is subjected to an alkali cleaning treatment to form a tower base structure 51 .

[0064] like Figure 2 As shown, a tower base structure 51 is formed on the back side of the substrate 5, wherein L represents the lateral dimension of the tower base structure 51, the lateral dimension L of the tower base structure 51 is 9-13 μm, indicating a large tower base structure, and the lateral dimension L of the tower base structure 51 is 7-8 μm, indicating a small tower base structure, wherein the flatness of the large tower base structure is higher than that of the small tower base structure.

[0065] It should be noted that, in practical applications, the present invention does not specifically limit the type of the tower base structure 51 on the back of the substrate 5. For example, the back of the substrate 5 can be set to a large tower base structure, or the back of the substrate 5 can be set to a small tower base structure, etc. Such adjustments and changes to the tower base structure 51 on the back of the substrate 5 do not deviate from the principle and scope of the present invention, and should be included in the protection scope of the present invention.

[0066] Preferably, the back side of the substrate 5 is a large tower base structure.

[0067] It should be noted that the present invention does not impose any particular limitation on the lateral size of the tower base structure 51 on the back of the substrate 5. For example, the lateral size of the tower base structure 51 can be set to 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, or a range consisting of any two of these values.

[0068] Preferably, the lateral dimension of the tower base structure 51 on the back side of the substrate 5 is 9 μm-13 μm.

[0069] By setting the lateral dimension of the tower base structure 51 on the back side of the substrate 5 to 9μm-13μm, compared with the small tower base structure, the flatness of the back side of the substrate 5 can be further improved, the uniformity of the back side structure can be improved, the back side reflectivity can be increased, the absorption of light can be increased, and the passivation effect of the back side can be improved, which in turn helps to improve the performance of the battery.

[0070] More preferably, the transverse dimension of the tower base structure 51 is 9-11 μm.

[0071] It should be noted that, in practical applications, the present invention does not impose any limitation on the flatness of the tower base structure 51. For example, the flatness of the tower base structure 51 can be set to 0.20, 0.21, 0.22, 0.23, 0.24, 0.25, or a range consisting of any two of these values.

[0072] Preferably, the flatness of the tower base structure 51 is 0.20-0.25.

[0073] By setting the lateral dimension of the tower base structure 51 to 9-13μm, the flatness of the tower base structure 51 to 0.20-0.25, and the thickness of the tunnel oxide layer 7 prepared by the PECVD process to 1.5nm-2.0nm, the process matching can be better, so that the conversion efficiency of the prepared TOPcon battery can be higher, and there will be no water marks, and the overall performance of the prepared TOPcon battery is better.

[0074] It should be noted that the present invention does not impose any particular limitation on the alkali washing time of the alkali washing process. For example, the alkali washing time can be set to 220s, 222s, 224s, 226s, 228s, 230s, 232s, 234s, 236s, 238s, 240s or a range consisting of any two of these values.

[0075] Preferably, the alkali washing time of the alkali washing treatment is in the range of 220s-240s.

[0076] It should be noted that the present invention does not impose any particular limitation on the alkali washing temperature during the alkali washing process. For example, the alkali washing temperature can be set to 62°C, 62.5°C, 63°C, 63.5°C, 64°C, or a range consisting of any two of these values.

[0077] Preferably, the alkali washing temperature range of the alkali washing treatment is 62°C-64°C.

[0078] By controlling the alkali washing temperature and alkali washing time in the alkali polishing process, the lateral size and flatness of the tower base structure 51 on the back side of the substrate 5 can be controlled, so that the lateral size of the tower base structure 51 is controlled at 9μm-13μm, and the flatness of the tower base structure 51 is controlled at 0.20-0.25, which can improve the flatness of the back side of the substrate 5 and reduce the structural differences on the back side of the substrate 5 caused by the presence of the oxide layer 6.

[0079] Preferably, if Figure 3 As shown, the preparation method of the TOPcon battery of the present invention further comprises the following steps:

[0080] S4 : forming a polysilicon (poly) layer 8 on the back side of the tunnel oxide layer 7 .

[0081] Specifically, a polysilicon (poly) layer 8 is grown on the back side of the tunnel oxide layer 7 by using a plasma enhanced chemical vapor deposition (PECVD) process, and then an annealing treatment is performed.

[0082] Preferably, if Figure 3 As shown, before the substrate 5 is subjected to alkaline washing treatment, the method for preparing the TOPcon battery of the present invention further includes the following steps:

[0083] S01: cleaning and texturing the substrate 5;

[0084] S02 : Boron is diffused on the front surface of the substrate 5 in step S01 to form a PN junction, so as to form a diffusion layer 4 on the front surface of the substrate 5 .

[0085] Preferably, if Figure 3 As shown, the preparation method of the TOPcon battery of the present invention further comprises the following steps:

[0086] S5: A passivation layer 3 is formed on the front side of the substrate 5 obtained in step S4.

[0087] Specifically, an aluminum oxide layer is deposited on the front side of the substrate 5 obtained in step S4 using the ALD atomic layer deposition technology to obtain the passivation layer 3 .

[0088] It should be noted that, in practical applications, the present invention does not impose any limitation on the specific type of the passivation layer 3 .

[0089] For example, the passivation layer 3 includes at least one of aluminum oxide and silicon oxide.

[0090] More preferably, the passivation layer 3 is an aluminum oxide layer.

[0091] Preferably, if Figure 3 As shown, the preparation method of the TOPcon battery of the present invention further comprises the following steps:

[0092] S6: forming a front anti-reflection layer 2 and a back anti-reflection layer 9 on the front and back sides of the substrate 5 obtained in step S5, respectively.

[0093] It should be noted that the present invention does not impose any limitation on the order of forming the front anti-reflection layer 2 and the back anti-reflection layer 9. For example, the front anti-reflection layer 2 may be first formed on the front side of the substrate 5 obtained in step S5, and then the back anti-reflection layer 9 may be formed on the back side of the substrate 5. Alternatively, the back anti-reflection layer 9 may be first formed on the back side of the substrate 5 obtained in step S5, and then the front anti-reflection layer 2 may be formed on the front side of the substrate 5, and so on. Such adjustments and changes to the order of forming the front anti-reflection layer 2 and the back anti-reflection layer 9 do not deviate from the principle and scope of the present invention, and should be included in the protection scope of the present invention.

[0094] Preferably, if Figure 3 As shown, the step of "forming a front anti-reflection layer 2 and a back anti-reflection layer 9 on the front and back of the substrate 5 obtained in step S5, respectively" specifically includes:

[0095] S61: forming a front anti-reflection layer 2 on the front side of the substrate 5 obtained in step S5;

[0096] S62: forming a back surface anti-reflection layer 9 on the back surface of the substrate 5 obtained in step S5.

[0097] It should be noted that, in practical applications, the present invention does not impose any limitation on the specific type of the anti-reflection layer. For example, the anti-reflection layer may be configured to include at least one of silicon nitride, silicon oxynitride, and silicon oxide.

[0098] Further preferably, the anti-reflection layer is a silicon nitride layer.

[0099] Preferably, if Figure 3 As shown, the preparation method of the TOPcon battery of the present invention further comprises the following steps:

[0100] S7: A front electrode 1 and a back electrode 10 are formed on the front and back sides of the substrate 5 obtained in step S6, respectively.

[0101] Specifically, a front electrode 1 and a back electrode 10 are formed on the front and back of the substrate 5 respectively by screen printing process to produce a TOPcon battery.

[0102] It should be noted that, in practical applications, the present invention does not impose any limitation on the order of forming the front electrode 1 and the back electrode 10. For example, the front electrode 1 may be formed on the front of the substrate 5 obtained in step S6, and then the back electrode 10 may be formed on the back of the substrate 5, or the back electrode 10 may be formed on the back of the substrate 5 obtained in step S6, and then the front electrode 1 may be formed on the front of the substrate 5 obtained in step S6, and so on. Such adjustment and change of the order of forming the front electrode 1 and the back electrode 10 does not deviate from the principle and scope of the present invention, and should be included in the protection scope of the present invention.

[0103] Preferably, if Figure 3 As shown, the step of "forming a front electrode 1 and a back electrode 10 on the front and back of the substrate 5 obtained in step S6" specifically includes:

[0104] S71: forming a front electrode 1 on the front surface of the substrate 5 obtained in step S6;

[0105] S72: A back electrode 10 is formed on the back surface of the substrate 5 obtained in step S6.

[0106] In a second aspect, the present invention also provides a TOPcon battery.

[0107] Specifically, Figure 1 and Figure 2 As shown, the TOPcon battery of the present invention includes a substrate 5, an oxide layer 6 and a tunneling oxide layer 7 stacked in sequence on the back side of the substrate 5, the back side of the substrate 5 has a tower base structure 51, the oxide layer 6 is arranged on the tower base structure 51, wherein the tunneling oxide layer 7 is made by a PECVD process.

[0108] Preferably, if Figure 1 and Figure 2 As shown, the lateral dimension L of the tower base structure 51 is 9 μm-13 μm, the flatness of the tower base structure 51 is 0.20-0.25, and the thickness of the tunnel oxide layer 7 is 1.5 nm-2.0 nm.

[0109] Preferably, if Figure 1 As shown, the TOPcon cell of the present invention further includes a back anti-reflection layer 9 and a back electrode 10 which are sequentially stacked on the back of the polysilicon layer.

[0110] Preferably, if Figure 1 As shown, the TOPcon cell of the present invention further includes a diffusion layer 4, a passivation layer 3, a front anti-reflection layer 2 and a front electrode 1 which are sequentially stacked on the front side of the substrate 5.

[0111] It should be noted that, in practical applications, those skilled in the art may set the substrate 5 to an N-type silicon substrate, or may set the substrate 5 to a P-type silicon substrate, or may set the substrate 5 to any other possible type, and so on. Such adjustments and changes to the specific setting type of the substrate 5 do not deviate from the principle and scope of the present invention, and should be included in the protection scope of the present invention.

[0112] Preferably, the substrate 5 is an N-type silicon substrate.

[0113] The specific embodiments of the TOPcon battery of the present invention are described in detail below in conjunction with the following embodiments.

[0114] Embodiment 1:

[0115] The substrate 5 used in this embodiment is an N-type silicon substrate. The preparation method of the TOPcon battery in this embodiment includes the following steps:

[0116] (1) Cleaning and texturing the N-type silicon substrate;

[0117] (2) performing boron diffusion on the front surface of the N-type silicon substrate obtained in step (1) to form a PN junction;

[0118] (3) performing alkali polishing on the back side of the N-type silicon substrate obtained in step (2), i.e., performing alkali washing, water washing, post-washing, water washing, acid washing, water washing, slow pulling and drying in sequence,

[0119] In which, the alkaline washing process forms a tower base structure 51 on the back side of the N-type silicon substrate, the lateral dimension of the tower base structure 51 is 9-11 μm, the flatness sq of the tower base structure 51 is 0.22-0.24, the post-cleaning liquid of the post-cleaning treatment is hydrogen peroxide and sodium hydroxide solution, the pickling liquid of the pickling treatment is HCl solution, and an oxide layer 6 is formed on the tower base structure 51, and the thickness of the oxide layer 6 is 1.4 nm-1.8 nm;

[0120] (4) growing a tunneling oxide layer 7 of 1.5 nm to 2.0 nm on the back side of the N-type silicon substrate obtained in step (3) by plasma enhanced chemical vapor deposition (PECVD);

[0121] (5) growing a polysilicon (poly) layer 8 on the back side of the N-type silicon wafer obtained in step (4) by plasma enhanced chemical vapor deposition (PECVD) and performing annealing treatment;

[0122] (6) chemically mechanically polishing the N-type silicon substrate obtained in step (5), and cleaning it using an RCA process;

[0123] (7) depositing an aluminum oxide layer on the front side of the N-type silicon substrate obtained in step (6) using an atomic layer deposition technique;

[0124] (8) forming a front anti-reflection layer 2 on the front side of the N-type silicon substrate obtained in step (7), and forming a back anti-reflection layer 9 on the back side;

[0125] (9) The front electrode 1 is printed on the front side of the N-type silicon substrate 5 obtained in step (8), and the back electrode 10 is printed on the back side, and then sintered to obtain a TOPcon battery.

[0126] Embodiment 2:

[0127] The preparation method of Example 2 is substantially the same as that of Example 1, except that the lateral dimensions of the tower base structure 51 formed on the back side of the N-type silicon substrate during the alkaline washing process in step (3) are different.

[0128] In this embodiment, the tower base structure 51 formed on the back side of the N-type silicon substrate by the alkaline washing process has a lateral dimension of 11 μm-13 μm, and a flatness sq of 0.20-0.22.

[0129] Embodiment 3:

[0130] The preparation method of Example 3 is substantially the same as that of Example 1, except that the lateral dimensions of the tower base structure 51 formed on the back side of the N-type silicon substrate during the alkaline washing process in step (3) are different.

[0131] In this embodiment, the tower base structure 51 formed on the back side of the N-type silicon substrate by the alkaline washing process has a lateral size of 7 μm-8 μm, and a flatness sq of 0.30.

[0132] Comparative Example 1:

[0133] The preparation method of Comparative Example 1 is substantially the same as that of Example 1, except that the thickness of the tunneling oxide layer 7 formed in step (4) is different.

[0134] In this comparative example, the alkali washing process forms a tower base structure 51 on the back side of the N-type silicon substrate 5 with a lateral dimension of 9 μm-11 μm, a flatness sq of 0.22-0.24, and a thickness of the tunnel oxide layer 7 of 1 nm-1.4 nm.

[0135] Comparative Example 2:

[0136] The preparation method of comparative example 3 is basically the same as the preparation method of embodiment 1, except that: the lateral dimensions of the tower base structure 51 formed on the back side of the N-type silicon substrate 5 during the alkaline washing process in step (3) are different, and the thickness of the tunneling oxide layer 7 formed in step (4) is different.

[0137] In this comparative example, the alkali washing process forms a tower base structure 51 on the back side of the N-type silicon substrate 5 with a lateral dimension of 11 μm-13 μm, a flatness sq of 0.20-0.22, and a thickness of the tunnel oxide layer 7 of 1 nm-1.4 nm.

[0138] Comparative Example 3:

[0139] The preparation method of comparative example 3 is basically the same as the preparation method of embodiment 1, except that: the lateral dimensions of the tower base structure 51 formed on the back side of the N-type silicon substrate during the alkaline washing process in step (3) are different, and the thickness of the tunneling oxide layer 7 formed in step (4) is different.

[0140] In this comparative example, the lateral dimension of the tower base structure 51 formed on the back side of the N-type silicon substrate by the alkaline washing process is 7 μm-8 μm, the flatness sq of the tower base structure 51 is 0.30, and the thickness of the tunnel oxide layer 7 is 1 nm-1.4 nm.

[0141] Comparative Example 4:

[0142] The preparation method of the TOPcon battery in Comparative Example 4 is basically the same as the preparation method of the TOPcon battery in Example 1, except that the type of pickling solution used in the pickling treatment in step (3) is different.

[0143] In this comparative example, the types of pickling liquids used in the pickling treatment are HCl and HF.

[0144] Test method:

[0145] Test Example 1:

[0146] The electrical properties of the TOPcon batteries prepared in Examples 1 to 3 and Comparative Examples 1 to 4 were tested using an IV tester. The test results are shown in Table 1 below:

[0147] Table 1: Test data of embodiments and comparative examples

[0148] Test Example 2:

[0149] The TOPcon batteries prepared in Examples 1 to 3 and Comparative Examples 1 to 4 were subjected to EL testing using an EL testing machine. The test results are shown in FIG. Figure 4 and Figure 5 shown.

[0150] Among them, the EL test results of Examples 1 to 3 are as follows: Figure 4 As shown, there is no water mark in the prepared TOPcon battery. The EL test results of Comparative Examples 1 to 3 are as follows Figure 5 As shown, Figure 5 There are obvious water marks on the TOPcon batteries (the vertical white stripes within the frame are the water marks).

[0151] From Table 1 and Figure 4 , Figure 5 From the data we can see that:

[0152] 1. Comparing the data of Examples 1 to 3 with that of Comparative Example 4, the conversion efficiency of the TOPcon batteries prepared in Examples 1 to 3 is significantly higher than that of the TOPcon batteries prepared in Comparative Example 4. Since the pickling solutions of Examples 1 to 3 do not contain HF, the oxide layer 6 formed on the tower base structure 51 can effectively improve the tunneling oxide layer 7 subsequently prepared by the PECVD process, and improve the film formation uniformity and film formation quality. However, since the pickling solution in Comparative Example 4 contains HF, the oxide layer 6 formed in the post-cleaning process will react with HF and be removed. The tunneling oxide layer 6 subsequently prepared by the PECVD process has poor film formation uniformity, resulting in a low conversion efficiency of the prepared TOPcon battery.

[0153] Therefore, first forming an oxide layer 6 on the tower base structure 51, and then forming a tunnel oxide layer 7 on the oxide layer using a PECVD process can effectively improve the film formation quality of the tunnel oxide layer 7 subsequently prepared using the PECVD process and improve the conversion efficiency of the TOPcon battery.

[0154] 2. Comparing the data of Example 1 with Comparative Example 1, Example 2 with Comparative Example 2, and Example 3 with Comparative Example 3, the TOPcon batteries prepared in Examples 1 to 3 can effectively improve the problem of water marks, that is, adjusting the thickness of the tunneling oxide layer 7 to within the range of 1.5nm-2.0nm can effectively avoid the problem of water marks in the prepared TOPcon batteries due to the presence of the oxide layer 6, thereby avoiding the problem of poor appearance of the TOPcon batteries.

[0155] 3. Comparing Examples 1 to 3, although the TOPcon batteries prepared in Examples 1 to 3 can well avoid the problem of water marks caused by the presence of the oxide layer 6, since the conversion efficiency of the TOPcon battery prepared in Example 3 is relatively low, therefore, when the lateral dimension of the tower base structure 51 is in the range of 9-13 μm and the thickness of the tunneling oxide layer 7 is in the range of 1.5 nm-2.0 nm, it can not only avoid the problem of water marks caused by the presence of the oxide layer 6, but also make the conversion efficiency of the prepared TOPcon battery higher.

[0156] 4. Comparing Example 1 with Example 2, the conversion efficiency of the TOPcon battery prepared in Example 1 is higher than that in Example 2. Therefore, when the lateral dimension of the tower base structure 51 is in the range of 9-11 μm and the thickness of the tunneling oxide layer 7 is in the range of 1.5 nm-2.0 nm, the conversion efficiency of the prepared TOPcon battery is higher.

[0157] In addition, the present invention also provides a battery assembly, which includes any one of the TOPcon batteries introduced above.

[0158] So far, the technical solutions of the present invention have been described in conjunction with the preferred embodiments shown in the accompanying drawings. However, it is easy for those skilled in the art to understand that the protection scope of the present invention is obviously not limited to these specific embodiments. Without departing from the principle of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will fall within the protection scope of the present invention.

Claims

1. A method for preparing a TOPcon battery, characterized in that: The preparation method comprises the following steps: S1: forming a tower base structure on the back side of the substrate; S2: forming an oxide layer on the tower base structure; S3: forming a tunnel oxide layer on the oxide layer by using a PECVD process.

2. The method for preparing a TOPcon battery according to claim 1, characterized in that: The step of "forming an oxide layer on the tower base structure" specifically includes: The battery structure after forming the tower base structure is subjected to post-cleaning and pickling treatment in sequence to form the oxide layer. The post-cleaning solution of the post-cleaning treatment at least includes hydrogen peroxide, and the pickling solution of the pickling treatment does not contain HF.

3. The method for preparing a TOPcon battery according to claim 1, characterized in that: The lateral dimension of the tower base structure is 9 μm-13 μm, the flatness of the tower base structure is 0.20-0.25, and the thickness of the tunnel oxide layer is 1.5 nm-2.0 nm.

4. The method for preparing a TOPcon battery according to claim 1, characterized in that: The thickness of the oxide layer is 1.4nm-1.8nm.

5. The method for preparing a TOPcon battery according to claim 1, characterized in that: The step of "forming a tower base structure on the back side of the substrate" specifically includes: The back side of the substrate is subjected to an alkali cleaning treatment to form the tower base structure.

6. The method for preparing a TOPcon battery according to claim 5, characterized in that: The time range of the alkali washing treatment is 220s-240s, and the temperature range is 62-64°C.

7. A TOPcon battery, characterized in that: include: A substrate having a tower base structure on its back side; an oxide layer disposed on the tower base structure; as well as A tunneling oxide layer is arranged on the oxide layer, wherein the tunneling oxide layer is made by adopting a PECVD process.

8. The TOPcon battery according to claim 7, characterized in that The lateral dimension of the tower base structure is 9 μm-13 μm, the flatness of the tower base structure is 0.20-0.25, and the thickness of the tunnel oxide layer is 1.5 nm-2.0 nm.

9. The TOPcon battery according to claim 7, characterized in that The TOPcon battery also includes: A back anti-reflection layer and a back electrode are sequentially stacked on the tunnel oxide layer; A diffusion layer, a passivation layer, a front anti-reflection layer and a front electrode are sequentially stacked on the front side of the substrate.

10. A battery assembly, characterized in that: The battery assembly comprises the TOPcon battery according to any one of claims 7 to 9.

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