Tunneling oxide layer passivation contact cell and preparation method thereof

Abstract

The invention discloses a tunneling oxide layer passivation contact cell and a preparation method thereof. The tunneling oxide layer passivation contact cell comprises a silicon substrate, a tunneling oxide layer and a polycrystalline silicon layer, the tunneling oxide layer is arranged on one side of the silicon substrate; the polycrystalline silicon layer is arranged on one side, far away from the silicon substrate, of the tunneling oxide layer; the side, away from the tunneling oxide layer, of the silicon substrate comprises a suede structure, the suede structure comprises a plurality of hole-shaped structures, and the hole-shaped structures are arranged in the silicon substrate at intervals and communicate with the surface of the side, away from the tunneling oxide layer, of the silicon substrate. According to the technical scheme of the invention, the textured structure enhances the light trapping effect, so that the incident light can be completely absorbed, and the characteristics of surface passivation, electrode contact and the like can be improved, thereby improving the collection efficiency of current carriers. Meanwhile, the embodiment of the invention also comprises a TOPCon technology, the TOPCon technology can better absorb photons on the back surface, and the combination of the suede structure and the TOPCon technology can greatly improve the conversion efficiency of the cell and achieve the effects of reducing cost and improving efficiency.

Description

Technical Field

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

[0002] With the development of the photovoltaic industry, in order to achieve the cost of solar cell electricity generation equal to that of traditional energy thermal power generation, grid parity, or even lower, reducing energy loss and improving battery conversion efficiency are one of the most effective ways. By changing the battery velvet structure and battery stacking structure, and performing high-quality passivation on the new structure, the absorption capacity of photons on the battery surface can be improved, thereby improving battery conversion, increasing the single-chip power, and thus increasing the power generation of the component and reducing the cost per kilowatt-hour.

[0003] Changing the velvet structure of the battery refers to performing a velvet treatment on the front of the battery to increase the battery's absorption of sunlight, thereby improving the carrier collection efficiency. Specifically, a positive pyramid velvet structure is generally prepared on the surface of the silicon substrate, but when the light is not direct or the ambient light is mostly scattered light, the structure has a poor absorption rate for light, which affects the improvement of battery efficiency. Summary of the invention

[0004] The present invention provides a tunneling oxide layer passivation contact cell and a preparation method thereof, so as to solve the problems of poor light absorption rate and poor photoelectric conversion efficiency of the cell in the prior art.

[0005] According to one aspect of the present invention, there is provided a tunneling oxide layer passivation contact cell, characterized in that it comprises: a silicon substrate, a tunneling oxide layer and a polysilicon layer;

[0006] The tunnel oxide layer is arranged on one side of the silicon substrate; the polysilicon layer is arranged on the side of the tunnel oxide layer away from the silicon substrate;

[0007] The side of the silicon substrate away from the tunnel oxide layer includes a velvet structure, the velvet structure includes a plurality of pore structures, the pore structures are arranged in the silicon substrate at intervals and communicated with the surface of the silicon substrate away from the tunnel oxide layer.

[0008] Optionally, the hole-shaped structure includes a first sub-section and a second sub-section that are connected; the second sub-section is located on a side of the first sub-section close to the tunnel oxide layer;

[0009] The first section is a cylindrical hole, and the second section is a tapered hole.

[0010] Optionally, the pore size of the first section ranges from 150 μm to 250 μm.

[0011] Optionally, the reflectivity of the silicon substrate at a side away from the tunnel oxide layer is in a range of 4.95%-5.05%.

[0012] Optionally, the silicon substrate is an N-type silicon substrate.

[0013] Optionally, the tunnel oxide layer passivation contact cell further includes a PN junction, a passivation layer, a front anti-reflection layer, a back anti-reflection layer and an electrode;

[0014] The PN junction is arranged on the side of the silicon substrate having the velvet structure;

[0015] The passivation layer is arranged on the side of the PN junction away from the silicon substrate;

[0016] The front anti-reflection layer is arranged on the side of the passivation layer away from the PN junction;

[0017] The back anti-reflection layer is arranged on the side of the polysilicon layer away from the tunnel oxide layer;

[0018] The electrodes are respectively arranged on a side of the front anti-reflection layer away from the passivation layer and a side of the back anti-reflection layer away from the polysilicon layer.

[0019] According to another aspect of the present invention, a method for preparing a tunneling oxide layer passivation contact cell is provided, which is used to prepare a tunneling oxide layer passivation contact cell, and the preparation method comprises:

[0020] Providing a silicon substrate and cleaning the silicon substrate with a cleaning solution to form a velvet structure on one side of the silicon substrate; wherein the cleaning solution includes silver nitrate;

[0021] A tunneling oxide layer is prepared on a side of the silicon substrate away from the velvet structure;

[0022] A polysilicon layer is prepared on the side of the tunnel oxide layer away from the silicon substrate.

[0023] Optionally, providing a silicon substrate and cleaning the silicon substrate with a cleaning solution to form a velvet structure on one side of the silicon substrate includes:

[0024] Providing a silicon substrate and cleaning the silicon substrate with a first cleaning solution to form a velvet structure on one side of the silicon substrate; wherein the first cleaning solution includes silver nitrate;

[0025] The silicon substrate is continuously cleaned with a second cleaning solution to remove silver ions in the textured structure.

[0026] Optionally, a tunneling oxide layer is formed on a side of the silicon substrate away from the suede structure, comprising:

[0027] A silicon oxide layer is prepared on a side of the silicon substrate away from the suede structure;

[0028] A silane layer is prepared on the side of the silicon oxide layer away from the silicon substrate to form a tunneling oxide layer;

[0029] A polysilicon layer is formed on a side of the tunnel oxide layer away from the silicon substrate, comprising:

[0030] The silane layer is doped with phosphorus to form a polysilicon layer.

[0031] Optionally, before preparing the tunneling oxide layer on the side of the silicon substrate away from the suede structure, the method further includes:

[0032] A PN junction is prepared on the side of the silicon substrate having a suede structure;

[0033] After a polysilicon layer is prepared on a side of the tunnel oxide layer away from the silicon substrate, the method further comprises:

[0034] A passivation layer is prepared on the side of the PN junction away from the silicon substrate;

[0035] A front anti-reflection layer is prepared on the side of the passivation layer away from the PN junction;

[0036] A back anti-reflection layer is formed on the side of the polysilicon layer away from the tunnel oxide layer;

[0037] Electrodes are prepared respectively on the side of the front anti-reflection layer away from the passivation layer and the side of the back anti-reflection layer away from the polysilicon layer.

[0038] The technical solution of the present invention is to set a velvet structure in the tunneling oxide layer passivation contact cell, and the velvet structure includes a hole structure, and the hole structure part penetrates the silicon substrate and is arranged at intervals in the silicon substrate, thereby changing the pyramid structure in the traditional velvet structure to a hole structure, enhancing the light trapping effect, reducing the reflectivity, so that the incident light can be completely absorbed and can improve the surface passivation and electrode contact characteristics, thereby improving the carrier collection efficiency. At the same time, the embodiment of the present invention also includes TOPCon technology, which can better absorb the photons on the back side. The combination of the velvet structure and the TOPCon technology can greatly improve the efficiency of battery conversion and achieve the effect of reducing costs and increasing efficiency.

[0039] It should be understood that the contents described in this section are not intended to identify the key or important features of the embodiments of the present invention, nor are they intended to limit the scope of the present invention. Other features of the present invention will become easily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0041] Figure 1 is a schematic structural diagram of a tunnel oxide layer passivation contact cell provided according to an embodiment of the present invention;

[0042] Figure 2is a schematic structural diagram of a velvet structure provided according to an embodiment of the present invention;

[0043] Figure 3 It is a schematic diagram of the structure of a battery in the prior art;

[0044] Figure 4 It is a structural schematic diagram of a suede structure in the prior art;

[0045] Figure 5 It is a flow chart of a method for preparing a first tunnel oxide layer passivation contact cell provided in an embodiment of the present invention;

[0046] Figure 6 yes Figure 5 Structural diagram corresponding to the preparation method;

[0047] Figure 7 is a flow chart of a second method for preparing a tunnel oxide layer passivation contact cell provided in an embodiment of the present invention;

[0048] Figure 8 is a flow chart of a third method for preparing a tunnel oxide layer passivation contact cell provided in an embodiment of the present invention;

[0049] Fig. 9 is a flow chart of a third method for preparing a tunnel oxide layer passivation contact cell provided in an embodiment of the present invention;

[0050] Fig.10 yes Fig. 9 Structural diagram corresponding to the preparation method. DETAILED DESCRIPTION

[0051] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0052] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0053] Figure 1 is a schematic structural diagram of a tunnel oxide layer passivation contact cell provided according to an embodiment of the present invention, Figure 2 is a schematic structural diagram of a velvet structure provided according to an embodiment of the present invention, Figure 3 It is a schematic diagram of the structure of a battery in the prior art. Figure 4 It is a schematic diagram of the structure of the velvet structure in the prior art. Figure 1 , Figure 2 , Figure 3 and Figure 4 As shown, the tunnel oxide layer passivation contact cell comprises: a silicon substrate 1, a tunnel oxide layer 2 and a polysilicon layer 3;

[0054] The tunnel oxide layer 2 is arranged on one side of the silicon substrate 1; the polysilicon layer 3 is arranged on the side of the tunnel oxide layer 2 away from the silicon substrate 1;

[0055] The side of the silicon substrate 1 away from the tunneling oxide layer 2 includes a velvet structure 4 , which includes a plurality of pore structures arranged at intervals in the silicon substrate 1 and connected to the surface of the silicon substrate 1 away from the tunneling oxide layer 2 .

[0056] Among them, the tunnel oxide layer 2 passivating contact battery (Tunnel Oxide Passivating Contacts, TOPCon) battery is mainly composed of an extremely thin oxide layer and a polysilicon thin layer, namely the tunnel oxide layer 2 and the polysilicon layer 3 in the embodiment of the present invention. After doping activation, the polysilicon layer 3 acts together with the tunnel oxide layer 2 on the back surface, has a good passivation effect on minority carriers, and has excellent conductivity for majority carriers. By performing a metallization process on the surface, a passivated contact without opening a hole can be obtained, which is an important way to increase the voltage and can significantly reduce the metal contact composite current.

[0057] Among them, in the embodiment of the present invention, a velvet structure 4 is arranged on the side of the silicon substrate 1 away from the tunneling oxide layer 2, that is, the front side of the battery, and the velvet structure 4 is formed by velveting the silicon substrate 1. The velvet structure 4 in the prior art is often a "pyramid" structure, and the velvet structure 4 in the embodiment of the present invention includes a plurality of hole structures, that is, a plurality of arrays of hole structures are included in the silicon substrate 1, and the hole structure part penetrates the silicon substrate 1 and is arranged at intervals in the silicon substrate 1. Compared with the prior art, the velvet structure 4 in the embodiment of the present invention can be refracted multiple times in the hole structure when the light is incident to enter the inside of the hole structure, thereby enhancing the light trapping effect, so that the incident light can be completely absorbed, reducing the reflectivity of sunlight and improving the properties such as surface passivation and electrode 9 contact, thereby improving the collection efficiency of carriers. At the same time, the embodiment of the present invention also includes TOPCon technology, which can better absorb the photons on the back side. The combination of the velvet structure 4 and the TOPCon technology can greatly improve the efficiency of battery conversion and achieve the effect of reducing costs and increasing efficiency.

[0058] It is understandable that the method for improving the conversion efficiency of the battery includes changing the battery velvet structure 4 and the battery stacking structure, and the TOPCon technology used in the embodiment of the present invention also changes the pyramid structure in the traditional velvet structure 4 to a hole-shaped structure, thereby enhancing the light trapping effect, reducing the reflectivity, and improving the photoelectric conversion efficiency. At the same time, the velvet structure 4 including the hole-shaped structure can also improve the color difference problem caused by the cutting of the silicon substrate 1, and improve the utilization rate of the silicon wafer; at the same time, it may reduce the risk of broken grid caused by the overlap of the printed grid line and the line mark. Therefore, by using the structure provided by the embodiment of the present invention, the battery efficiency can be improved by 0.3%, and the battery yield can be improved by 1%, thereby greatly reducing the battery cost, thereby achieving a reduction in the cost per kilowatt-hour.

[0059] Exemplarily, the surface of the silicon substrate 1 is first textured to remove the damaged layer on the surface of the original silicon substrate 1 and prepare the velvet structure 4 of the porous structure. In the cleaning process, the silicon substrate 1 is placed in a texturing tank containing a solution of a silver nitrate additive, and then sequentially passes through a water tank, a nitric acid tank, a water tank, a KOH tank, a water tank, a HCL+H2O2 mixed acid tank, a hot water tank, and a drying tank to form a preliminary velvet structure 4. In this process, it can be monitored whether the velvet structure 4 is formed in a standard manner, that is, whether the weight loss of the silicon substrate 1 is between 0.2±0.05g, whether the reflectivity of the velvet structure 4 is controlled between 4%±1%, and whether the pore size of the porous structure is controlled between 200um±50um. After the velvet structure 4 is initially prepared, a secondary cleaning is required to remove the silver ions in the velvet structure 4. Then, the silicon substrate 1 is placed in a velvet making tank with a second cleaning solution added thereto to perform velvet repair. During this process, it is possible to monitor whether the velvet structure 4 is formed in a standard manner, that is, whether the reflectivity of the velvet structure 4 is controlled between 5%±0.05%. After the velvet structure 4 is prepared, a tunneling oxide layer 2 and a polysilicon layer 3 can be prepared on the back of the silicon substrate 1.

[0060] In some embodiments, the reflectivity of the side of the silicon substrate 1 away from the tunneling oxide layer 2 is in the range of 4.95%-5.05%. Since the side of the silicon substrate 1 away from the tunneling oxide layer 2 mainly relies on the velvet structure 4 to reduce the reflectivity and improve the light absorption capacity, the velvet structure 4 in the embodiment of the present invention is set, so that the reflectivity of the side of the silicon substrate 1 away from the tunneling oxide layer 2 is in the range of 4.95%-5.05%, while the pyramid-shaped velvet structure 4 in the prior art is generally 9.95%-10.05%. It can be seen that the velvet structure 4 in the embodiment of the present invention can greatly reduce the reflectivity and increase the refractive stroke of photons.

[0061] In some embodiments, the silicon substrate 1 is an N-type silicon substrate. The N-type silicon substrate has good electrical conductivity, and by utilizing the anisotropic corrosion of silicon in the N-type silicon substrate, a silver nitrate solution is added to the texturing solution, thereby forming a pore-like textured surface structure 4 on the N-type silicon substrate, thereby improving the efficiency of photoelectric conversion.

[0062] The technical solution of the embodiment of the present invention is to set a velvet structure in the tunneling oxide layer passivation contact cell, and the velvet structure includes a hole structure, and the hole structure partially penetrates the silicon substrate and is arranged at intervals in the silicon substrate, thereby changing the pyramid structure in the traditional velvet structure to a hole structure, enhancing the light trapping effect, reducing the reflectivity, so that the incident light can be completely absorbed and can improve the surface passivation and electrode contact characteristics, thereby improving the carrier collection efficiency. At the same time, the embodiment of the present invention also includes TOPCon technology, which can better absorb the photons on the back side. The combination of the velvet structure and the TOPCon technology can greatly improve the efficiency of battery conversion and achieve the effect of reducing costs and increasing efficiency.

[0063] Optional, continue to refer to Figure 1 As shown, the hole-shaped structure includes a first sub-portion 41 and a second sub-portion 42 that are connected; the second sub-portion 42 is located on a side of the first sub-portion 41 close to the tunnel oxide layer 2;

[0064] The first section 41 is a cylindrical hole, and the second section 42 is a tapered hole.

[0065] The porous structure includes a first section 41 and a second section 42 which are connected. The first section 41 and the second section 42 can be formed integrally in the texturing tank. The first section 41 and the second section 42 are connected. The first section 41 is a columnar hole, and the second section 42 is a conical hole. Since the porous structure is formed by the reaction and corrosion of the texturing solution, the concentration of the silver nitrate additive in the texturing solution will affect the formation shape and rate of the porous structure, and the concentration of the silver nitrate additive will also decrease as time increases during the corrosion process, which will cause the second section 42 to be insufficient to form a columnar hole, and form a conical hole.

[0066] It is understandable that the depth, density and aperture of the porous structure will affect the absorption and reflection of light. Therefore, setting the first section 41 as a cylindrical hole and the second section 42 as a conical hole can further increase the depth of the porous structure, making it more difficult for light to be reflected from the porous structure, thereby further improving the light absorption capacity.

[0067] The technical solution of the embodiment of the present invention is to set a connected first division and a second division in the porous structure, wherein the first division is a cylindrical hole and the second division is a conical hole. This ensures the depth of the porous structure without increasing the process flow, making it less likely for light to be reflected from the porous structure, thereby improving the light absorption capacity.

[0068] Optionally, the pore size of the first section 41 ranges from 150 μm to 250 μm.

[0069] The aperture of the first section 41 may be the diameter of the cross section of the first section 41 . Since the first section 41 and the second section 42 are connected, the aperture of the first section 41 is the maximum aperture of the second section 42 .

[0070] It is understandable that the aperture and distribution density of the pore structure will affect the absorption and reflection of light, so the aperture range of the first section 41 is limited to 150 μm-250 μm to ensure the reflection and absorption capabilities of light.

[0071] Optional, continue to refer to Figure 1 As shown, the tunnel oxide layer 2 passivation contact cell also includes a PN junction 5, a passivation layer 6, a front anti-reflection layer 7, a back anti-reflection layer 8 and an electrode 9;

[0072] The PN junction 5 is arranged on the side of the silicon substrate 1 having the velvet structure 4;

[0073] The passivation layer 6 is arranged on the side of the PN junction 5 away from the silicon substrate 1;

[0074] The front anti-reflection layer 7 is arranged on the side of the passivation layer 6 away from the PN junction 5;

[0075] The back anti-reflection layer 8 is arranged on the side of the polysilicon layer 3 away from the tunnel oxide layer 2;

[0076] The electrodes 9 are respectively arranged on the side of the front anti-reflection layer 7 away from the passivation layer 6 and the side of the back anti-reflection layer 8 away from the polysilicon layer 3 .

[0077] The PN junction 5 can be prepared by preparing a P-type semiconductor and an N-type semiconductor in the same film layer. The solar cell requires a large-area PN junction 5 to realize the conversion of light energy into electrical energy, so the PN junction 5 is prepared on the side of the silicon substrate 1 with the velvet structure 4.

[0078] The passivation layer 6 can effectively reduce the carrier density on the surface of the silicon substrate 1, improve the life of the silicon substrate 1 and the performance of the battery, so the passivation layer 6 is disposed on the side of the PN junction 5 away from the silicon substrate 1. In some embodiments, the passivation layer 6 may include aluminum oxide.

[0079] Among them, the front anti-reflection layer 7 and the back anti-reflection layer 8 can improve the absorption of sunlight by the battery, reduce light loss, and improve conversion efficiency, so the front and back of the battery are respectively provided with the front anti-reflection layer 7 and the back anti-reflection layer 8. In some embodiments, the front anti-reflection layer 7 and the back anti-reflection layer 8 may include one or more thin films of silicon oxide, silicon oxynitride and silicon nitride.

[0080] Among them, the electrode 9 can be divided into a front electrode 9 and a back electrode 9. The electrode 9 can be formed on both the back and front of the battery by printing low-temperature silver paste on the front and back of the passivation contact battery of the tunneling oxide layer 2 respectively. The wet weight at this time can be controlled between 95-105 mg.

[0081] In some embodiments, after the film layer of the tunnel oxide layer 2 passivating contact battery is prepared, the electrode 9 is required to form a good ohmic contact with the silicon substrate 1 by laser sintering technology. The battery is processed by laser induced attenuation technology, and the laser is used to locally scan the surface of the tunnel oxide layer 2 passivating contact battery to induce the injection of high charge carriers, and further form a good ohmic contact.

[0082] The technical solution of the embodiment of the present invention ensures the normal operation of the tunneling oxide layer passivation contact cell and improves the cell conversion efficiency by continuing to prepare the PN junction, passivation layer, front anti-reflection layer, back anti-reflection layer and electrode in the tunneling oxide layer passivation contact cell.

[0083] Based on the same inventive concept, Figure 5 is a flow chart of a method for preparing a first tunnel oxide layer passivation contact cell according to an embodiment of the present invention. Figure 6 yes Figure 5 The structural diagram corresponding to the preparation method, combined with Figure 3 , Figure 5 and Figure 6 As shown, an embodiment of the present invention further provides a method for preparing a tunneling oxide layer passivation contact cell, which is used to prepare a tunneling oxide layer passivation contact cell. The preparation method includes:

[0084] S10, providing a silicon substrate and cleaning the silicon substrate with a cleaning solution to form a velvet structure on one side of the silicon substrate. The cleaning solution includes silver nitrate. Figure 6 (a) Steps shown.

[0085] The silicon substrate 1 may be an N-type silicon substrate. First, a velvet structure 4 is prepared on one side of the silicon substrate 1. Since the silver nitrate solution can corrode the silicon substrate 1, the silicon substrate 1 is placed in a velvet-making tank containing a silver nitrate additive cleaning solution. The silver ions therein can react with the silicon substrate 1 while corroding to play a role of digging holes, thereby forming a velvet structure 4 with a porous structure.

[0086] S11, prepare a tunneling oxide layer on the side of the silicon substrate away from the velvet structure. Figure 6 (b) as shown in step.

[0087] S12, preparing a polysilicon layer on the side of the tunnel oxide layer away from the silicon substrate. Figure 6 (c) as shown in step.

[0088] Among them, a tunneling oxide layer 2 and a polysilicon layer 3 are prepared on the side of the silicon substrate 1 away from the velvet structure 4. After being doped and activated, the polysilicon layer 3 acts together with the tunneling oxide layer 2 on the back surface, has a good passivation effect on minority carriers, and has excellent conductivity for majority carriers. By performing a metallization process on the surface, a passivated contact without opening a hole can be obtained, which is an important way to increase the voltage and can significantly reduce the metal contact composite current.

[0089] It can be understood that, taking the N-type silicon substrate as an example, in the prior art, HF and HNO3 are often set in the cleaning solution to prepare the velvet structure 4, but the velvet structure 4 after corrosion by this cleaning solution is a pyramid structure, and in the embodiment of the present invention, silver nitrate is added to the cleaning solution so that the silver nitrate can corrode and react with the silicon substrate 1 to form a porous structure. Compared with the prior art, when the light is incident, it can be refracted multiple times in the porous structure to enter the interior of the porous structure, which enhances the light trapping effect, so that the incident light can be completely absorbed, the reflectivity of the sunlight can be reduced, and the surface passivation and electrode 9 contact characteristics can be improved, thereby improving the collection efficiency of carriers. At the same time, the embodiment of the present invention also includes TOPCon technology, which can better absorb the photons on the back. The combination of the velvet structure 4 and the TOPCon technology can greatly improve the efficiency of battery conversion and achieve the effect of reducing costs and increasing efficiency.

[0090] The technical solution of the embodiment of the present invention is to add silver nitrate to the cleaning solution in the tunneling oxide layer passivation contact cell, so that the velvet structure is changed from the traditional pyramid structure to a hole structure, thereby enhancing the light trapping effect and reducing the reflectivity, so that the incident light can be completely absorbed and the surface passivation and electrode contact characteristics can be improved, thereby improving the carrier collection efficiency. At the same time, the embodiment of the present invention also includes TOPCon technology, which can better absorb the photons on the back side. The combination of the velvet structure and the TOPCon technology can greatly improve the efficiency of battery conversion and achieve the effect of reducing costs and increasing efficiency.

[0091] Based on the above embodiments, Figure 7 is a flow chart of a second method for preparing a tunnel oxide layer passivation contact cell according to an embodiment of the present invention, combined with Figure 7 and Figure 6 As shown, the preparation method comprises:

[0092] S20, providing a silicon substrate and cleaning the silicon substrate with a first cleaning solution to form a velvet structure on one side of the silicon substrate, wherein the first cleaning solution includes silver nitrate.

[0093] Among them, the texturing step may include two parts to ensure the standardization and normativeness of the texturing structure. For example, Table 1 shows the specific process and parameters of step S20. Combined with the S20 shown in Table 1, the silicon substrate 1 is placed in a texturing tank containing a solution of silver nitrate additive, and then passes through a water tank, a nitric acid tank, a water tank, a KOH tank, a water tank, a HCL+H2O2 mixed acid tank, a hot water tank, and a drying tank in sequence to form a preliminary velvet structure 4. During this process, it can be monitored whether the velvet structure 4 is formed in a standard manner, that is, whether the weight loss of the silicon substrate 1 is between 0.2±0.05g, whether the reflectivity of the velvet structure 4 is controlled between 4%±1%, and whether the pore size of the porous structure is controlled between 200um±50um.

[0094] Table 1

[0095]

[0096]

[0097] S21, continue to use the second cleaning solution to clean the silicon substrate to remove silver ions in the suede structure.

[0098] Among them, in order to further remove the silver ions in the velvet structure 4, S21 is added, the second step of the cleaning process. Exemplarily, Table 2 shows the specific process and parameters of step S21. Combined with Table 2, the final velvet structure 4 is obtained by sequentially passing through the pre-cleaning tank, water tank, velvet tank, water tank, sampling grass, water tank, pickling tank, water tank and slow pulling and drying. This step can monitor the reflectivity of the velvet structure 4 between 5% ± 0.05%. Compared with the reflectivity of the traditional pyramid structure (10% ± 0.05%), it is reduced by half, effectively increasing the refraction stroke of photons, thereby reducing the reflectivity.

[0099] Table 2

[0100]

[0101]

[0102] S22. Prepare a tunneling oxide layer on the side of the silicon substrate away from the suede structure.

[0103] S23, preparing a polysilicon layer on a side of the tunnel oxide layer away from the silicon substrate.

[0104] The technical solution of the embodiment of the present invention requires secondary cleaning after the initial preparation of the velvet structure to remove silver ions in the velvet structure, while continuing to monitor the formation and parameters of the velvet structure to ensure the light absorption capacity of the velvet structure and increase the refraction distance of photons.

[0105] Based on the above embodiments, Figure 8 is a flow chart of a third method for preparing a tunnel oxide layer passivation contact cell according to an embodiment of the present invention, combined with Figure 6 and Figure 8 As shown, the preparation method comprises:

[0106] S30, providing a silicon substrate and cleaning the silicon substrate with a cleaning solution to form a velvet structure on one side of the silicon substrate, wherein the cleaning solution includes silver nitrate.

[0107] S31. Prepare a silicon oxide layer on the side of the silicon substrate away from the suede structure.

[0108] After the velvet structure 4 is prepared, a silicon oxide layer can be prepared on the side of the silicon substrate 1 away from the velvet structure 4. For example, Table 3 shows the specific process and parameters of step S31. In combination with Table 3, a silicon oxide layer is first prepared on the back side, and then a silane layer is deposited to form a tunneling oxide layer 2. The thickness of the tunneling oxide layer 2 is controlled to be about 140±10nm.

[0109] Table 3

[0110]

[0111] S32, preparing a silane layer on the side of the silicon oxide layer away from the silicon substrate to form a tunneling oxide layer.

[0112] S33, doping the silane layer with phosphorus to form a polysilicon layer.

[0113] After preparing the silane structure, phosphorus doping is continued, and a polysilicon layer 3 is formed at a high temperature. In this step, the square resistance is controlled between 45±10Ω. For example, Table 4 shows the specific process and parameters of step S33, and the polysilicon layer 3 is formed in combination with Table 4.

[0114] Table 4

[0115]

[0116] In some embodiments, after the tunnel oxide layer 2 and the polysilicon layer 3 are prepared, a dephosphorus silicon glass step and a cleaning step are performed. Table 5 shows the dephosphorus silicon glass step and parameters. Table 6 shows the cleaning step and parameters.

[0117] Table 5

[0118]

[0119]

[0120] Table 6

[0121]

[0122] The technical solution of the embodiment of the present invention prepares a tunneling oxide layer and a polysilicon layer based on a porous velvet structure, and utilizes TOPCon technology to better absorb photons on the back side. The combination of the velvet structure and TOPCon technology can greatly improve the efficiency of battery conversion and achieve the effect of reducing costs and increasing efficiency.

[0123] Based on the above embodiments, Fig. 9 is a flow chart of a third method for preparing a tunnel oxide layer passivation contact cell according to an embodiment of the present invention, Fig.10 yes Fig. 9 The structural diagram corresponding to the preparation method, combined with Fig. 9 and Fig.10 As shown, the preparation method comprises:

[0124] S40, providing a silicon substrate and cleaning the silicon substrate with a cleaning solution to form a velvet structure on one side of the silicon substrate. The cleaning solution includes silver nitrate. Fig.10 As shown in step (d).

[0125] S41, prepare a PN junction on the side of the silicon substrate having a suede structure. Fig.10 As shown in step (e).

[0126] The PN junction 5 can be prepared by preparing a P-type semiconductor and an N-type semiconductor in the same film layer. The solar cell requires a large-area PN junction 5 to realize the conversion of light energy into electrical energy, so the PN junction 5 is prepared on the side of the silicon substrate 1 with the velvet structure 4.

[0127] For example, the specific process and parameters of step S41 are shown in Table 7. As shown in Table 7, the PN junction 5 is prepared by a boron diffusion process, and the diffusion square resistance is controlled between 320±50Ω during the preparation of the PN junction 5.

[0128] Table 7

[0129]

[0130]

[0131] In some embodiments, before preparing the tunneling oxide layer 2, a borosilicate glass removal and alkali polishing process is also included. Table 8 shows the process flow and parameters of the borosilicate glass removal. Table 9 shows the alkali polishing process and parameters. At the same time, after the borosilicate glass removal and alkali polishing process, it can be monitored whether the reflectivity of the back of the battery is between 40% ± 10%, whether the battery weight reduction is controlled between 0.2g ± 0.05g, and whether the thickness of the battery oxide layer is controlled at about 1.0 ± 0.1nm.

[0132] Table 8 Table 9

[0133]

[0134]

[0135] S42, preparing a tunneling oxide layer on the side of the silicon substrate away from the suede structure. Fig.10 As shown in step (f).

[0136] S43, preparing a polysilicon layer on the side of the tunnel oxide layer away from the silicon substrate. Fig.10 As shown in step (g).

[0137] S44, prepare a passivation layer on the side of the PN junction away from the silicon substrate. Fig.10 As shown in step (h).

[0138] The passivation layer 6 can effectively reduce the carrier density on the surface of the silicon substrate 1, improve the life of the silicon substrate 1 and the performance of the battery, so the passivation layer 6 is disposed on the side of the PN junction 5 away from the silicon substrate 1. In some embodiments, the passivation layer 6 may include aluminum oxide.

[0139] For example, the passivation layer 6 is continuously prepared on the front side of the battery, and the thickness of the passivation layer 6 can be controlled to be between 4±0.5 nm. Table 10 shows the process flow and parameters for preparing the passivation layer 6.

[0140] Table 10

[0141]

[0142]

[0143] S45, prepare a front anti-reflection layer on the side of the passivation layer away from the PN junction. Fig.10 As shown in step (i).

[0144] S46, preparing a back anti-reflection layer on the side of the polysilicon layer away from the tunnel oxide layer. Fig.10 As shown in step (j).

[0145] Among them, the front anti-reflection layer 7 and the back anti-reflection layer 8 can improve the absorption of sunlight by the battery, reduce light loss, and improve conversion efficiency, so the front and back of the battery are respectively provided with the front anti-reflection layer 7 and the back anti-reflection layer 8. In some embodiments, the front anti-reflection layer 7 and the back anti-reflection layer 8 may include one or more thin films of silicon oxide, silicon oxynitride and silicon nitride.

[0146] For example, 3-5 layers of silicon nitride anti-reflection layer are plated on the front of the battery to reduce the reflectivity. The film thickness is controlled between 70±5nm. Table 11 shows the preparation process and parameters of the front anti-reflection layer 7.

[0147] Table 11

[0148]

[0149]

[0150] After the front anti-reflection layer 7 is prepared, 3-5 layers of silicon nitride are plated on the back, and the film thickness is controlled between 80±5nm. Table 12 shows the process flow and parameters for preparing the back anti-reflection layer 8.

[0151] Table 12

[0152]

[0153] S47, preparing electrodes on the side of the front anti-reflection layer away from the passivation layer and the side of the back anti-reflection layer away from the polysilicon layer. Fig.10 As shown in step (k).

[0154] Among them, the electrode 9 can be divided into a front electrode 9 and a back electrode 9. The electrode 9 can be formed on both the back and front of the battery by printing low-temperature silver paste on the front and back of the passivation contact battery of the tunneling oxide layer 2 respectively. The wet weight at this time can be controlled between 95-105 mg.

[0155] In some embodiments, after the film layer of the tunnel oxide layer 2 passivating contact battery is prepared, the electrode 9 is required to form a good ohmic contact with the silicon substrate 1 by laser sintering technology. The battery is processed by laser induced attenuation technology, and the laser is used to locally scan the surface of the tunnel oxide layer 2 passivating contact battery to induce the injection of high charge carriers, and further form a good ohmic contact.

[0156] The technical solution of the embodiment of the present invention ensures the normal operation of the tunneling oxide layer passivation contact cell and improves the cell conversion efficiency by continuing to prepare the PN junction, passivation layer, front anti-reflection layer, back anti-reflection layer and electrode in the tunneling oxide layer passivation contact cell.

[0157] It should be understood that the various forms of processes shown above can be used to reorder, add or delete steps. For example, the steps described in the present invention can be executed in parallel, sequentially or in different orders, as long as the desired results of the technical solution of the present invention can be achieved, and this document does not limit this.

[0158] The above specific implementations do not constitute a limitation on the protection scope of the present invention. It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and substitutions can be made according to design requirements and other factors. Any modification, equivalent substitution and improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A tunneling oxide passivation contact cell, characterized in that: include: Silicon substrate, tunnel oxide layer and polysilicon layer; The tunneling oxide layer is arranged on one side of the silicon substrate; the polysilicon layer is arranged on a side of the tunneling oxide layer away from the silicon substrate; The silicon substrate comprises a velvet structure on a side away from the tunnel oxide layer. The velvet structure comprises a plurality of hole structures. The hole structures are arranged in the silicon substrate at intervals and communicated with a surface of the silicon substrate on a side away from the tunnel oxide layer.

2. The tunnel oxide passivation contact cell according to claim 1, characterized in that: The hole-shaped structure comprises a first sub-section and a second sub-section which are connected; the second sub-section is located on a side of the first sub-section close to the tunnel oxide layer; The first section is a cylindrical hole, and the second section is a tapered hole.

3. The tunneling oxide passivation contact cell according to claim 2, characterized in that: The pore size of the first section ranges from 150 μm to 250 μm.

4. The tunnel oxide passivation contact cell according to claim 1, characterized in that: The reflectivity of the side of the silicon substrate away from the tunnel oxide layer is in the range of 4.95%-5.05%.

5. The tunnel oxide passivation contact cell according to claim 1, characterized in that: The silicon substrate is an N-type silicon substrate.

6. The tunnel oxide passivation contact cell according to claim 1, characterized in that: The tunnel oxide layer passivation contact cell also includes a PN junction, a passivation layer, a front anti-reflection layer, a back anti-reflection layer and an electrode; The PN junction is arranged on the side of the silicon substrate having the velvet structure; The passivation layer is arranged on a side of the PN junction away from the silicon substrate; The front anti-reflection layer is arranged on the side of the passivation layer away from the PN junction; The back anti-reflection layer is arranged on a side of the polysilicon layer away from the tunnel oxide layer; The electrodes are respectively arranged on a side of the front anti-reflection layer away from the passivation layer and a side of the back anti-reflection layer away from the polysilicon layer.

7. A method for preparing a tunneling oxide layer passivation contact cell, characterized in that: Used to prepare the tunneling oxide layer passivation contact cell according to any one of claims 1 to 6, the preparation method comprising: Providing a silicon substrate and cleaning the silicon substrate with a cleaning solution to form a velvet structure on one side of the silicon substrate; wherein the cleaning solution includes silver nitrate; Preparing a tunneling oxide layer on a side of the silicon substrate away from the velvet structure; A polysilicon layer is prepared on a side of the tunnel oxide layer away from the silicon substrate.

8. The preparation method according to claim 7, characterized in that: Providing a silicon substrate and cleaning the silicon substrate with a cleaning solution to form a velvet structure on one side of the silicon substrate, comprising: Providing a silicon substrate and cleaning the silicon substrate with a first cleaning solution to form a velvet structure on one side of the silicon substrate; wherein the first cleaning solution includes silver nitrate; The silicon substrate is continuously cleaned with a second cleaning solution to remove silver ions in the textured structure.

9. The preparation method according to claim 7, characterized in that: The step of preparing a tunneling oxide layer on a side of the silicon substrate away from the velvet structure comprises: Preparing a silicon oxide layer on a side of the silicon substrate away from the velvet structure; Preparing a silane layer on the side of the silicon oxide layer away from the silicon substrate to form a tunneling oxide layer; The method comprises: preparing a polysilicon layer on a side of the tunnel oxide layer away from the silicon substrate, comprising: Phosphorus is doped into the silane layer to form a polysilicon layer.

10. The preparation method according to claim 7, characterized in that: Before preparing the tunnel oxide layer on the side of the silicon substrate away from the velvet structure, the method further comprises: Prepare a PN junction on the side of the silicon substrate having the velvet structure; After a polysilicon layer is prepared on a side of the tunnel oxide layer away from the silicon substrate, the method further comprises: Prepare a passivation layer on the side of the PN junction away from the silicon substrate; Preparing a front anti-reflection layer on a side of the passivation layer away from the PN junction; Preparing a back anti-reflection layer on a side of the polysilicon layer away from the tunnel oxide layer; Electrodes are respectively prepared on the side of the front anti-reflection layer away from the passivation layer and the side of the back anti-reflection layer away from the polysilicon layer.

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