Back-contact solar cell and fabrication method therefor

Abstract

The present application relates to a back-contact solar cell and a fabrication method therefor, the method comprising: providing a back-contact solar cell substrate, the back-contact solar cell substrate comprising a silicon substrate (100) and a first functional pattern layer (110) provided on the back surface of the silicon substrate, and the first functional pattern layer (110) comprising an insulating pattern layer; cleaning the back-contact solar cell substrate, the cleaning method comprising at least one cleaning cycle, each cleaning cycle comprising: using a first cleaning liquid to perform oxidizing cleaning on the back-contact solar cell substrate, the first cleaning liquid comprising an oxidizing basic cleaning liquid; and using a second cleaning liquid to perform secondary cleaning on the back-contact solar cell substrate subjected to oxidizing cleaning, the second cleaning liquid comprising a basic solution, and the basic solution being adapted to dissolving silicon oxides; and successively forming a second functional pattern layer (200) and an electrode layer on the back surface of the cleaned back-contact solar cell substrate.

Description

Back contact solar cell and method for manufacturing the same

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to Chinese Patent Application No. CN202411316878.6, filed on September 20, 2024, the contents of which are incorporated herein in their entirety. TECHNICAL FIELD

[0003] The present application relates to the technical field of solar cells, in particular to a back contact solar cell and a method for manufacturing the same. BACKGROUND

[0004] Compared with the traditional front electrode solar cell, the biggest difference of the back contact solar cell is that the PN junction and the metal electrode are moved to the back of the cell, so that there is no electrode on the front of the cell to block the light, thereby improving the light absorption and conversion efficiency.

[0005] As shown in FIG. 4, the back contact solar cell includes a silicon substrate 100, and N-type conductive regions 31 and P-type conductive regions 32 alternately arranged on the back of the silicon substrate. In order to realize the alternately arranged N-type conductive regions 31 and P-type conductive regions 32 to form a PN junction, when manufacturing the back contact solar cell, the intrinsic passivation layer and the doped layer of the N-type conductive region or the P-type conductive region need to be patterned and etched to obtain a back contact solar cell substrate, and then the intrinsic passivation layer and the doped layer of the other conductive type are plated on the back contact solar cell substrate.

[0006] However, the oil stains generated in the patterning and etching process, as well as the semiconductor material particles, will adhere to the surface of the back contact solar cell substrate and form traps and carrier recombination on the surface of the back contact solar cell substrate, thereby reducing the open-circuit voltage of the back contact solar cell and ultimately reducing the photoelectric conversion efficiency of the back contact solar cell.

[0007] For non-back contact solar cells, cleaning is performed after the texturing process. In order to remove organic residues such as oil stains, a cleaning solution containing an oxidizing agent needs to be used to clean the surface of the substrate.

[0008] When the back contact solar cell substrate is cleaned with an oxidizing agent, the oxidizing agent will react with the surface of the back contact solar cell substrate during the cleaning process, resulting in the formation of an oxide layer on the surface of the back contact solar cell substrate. In order to deposit and passivate amorphous silicon for subsequent processes, the conventional method is to use hydrofluoric acid to remove the oxide layer. Hydrofluoric acid reacts easily with the oxide layer, and at the same time, the dangling bonds on the surface of the silicon substrate are saturated with hydrogen, thereby obtaining good passivation performance of the silicon substrate. However, the hydrofluoric acid will also react with the insulating layer of the back contact solar cell substrate, resulting in damage to the insulating layer.

[0009] Therefore, how to effectively clean the back contact solar cell substrate without damaging the back contact solar cell substrate becomes a technical problem to be solved in the field. SUMMARY

[0010] The present application aims to solve the above technical problems in the related art. To this end, the present application provides a back contact solar cell and a preparation method thereof, which can effectively maintain the cleanliness of the surface of the silicon substrate to obtain higher photoelectric conversion efficiency.

[0011] To achieve the above object, the present application provides a method for preparing a back contact solar cell, comprising the following steps:

[0012] providing a back contact solar cell substrate, wherein the back contact solar cell substrate comprises a silicon substrate and a first functional pattern layer arranged on the back of the silicon substrate, and the first functional pattern layer comprises an insulating pattern layer;

[0013] cleaning the back contact solar cell substrate; the cleaning method comprises at least two cleaning periods, and each cleaning period comprises:

[0014] performing oxidation cleaning on the back contact solar cell substrate by using a first cleaning solution, wherein the first cleaning solution comprises an alkaline cleaning solution with oxidation property, and is used to remove surface dirt particles of the back contact solar cell substrate;

[0015] performing secondary cleaning on the back contact solar cell substrate after the oxidation cleaning by using a second cleaning solution, wherein the second cleaning solution comprises an alkali solution, and the alkali solution is suitable for etching the oxide of the silicon on the surface of the silicon substrate;

[0016] forming a second functional pattern layer and an electrode layer on the back of the cleaned back contact solar cell substrate in sequence.

[0017] In an embodiment, the method further comprises:

[0018] performing pickling on the back contact solar cell substrate obtained after the cleaning of at least one cleaning period by using a non-oxidizing acid.

[0019] In a specific embodiment, the non-oxidizing acid comprises hydrochloric acid; in a preferred embodiment, the concentration of the hydrochloric acid is 1% to 15% by volume.

[0020] In an embodiment, the cleaning period further comprises the following step performed between the step of oxidation cleaning and the step of secondary cleaning:

[0021] performing water cleaning on the back contact solar cell substrate after the oxidation cleaning.

[0022] In a specific embodiment, the number of cleaning cycles is 2-5.

[0023] In an embodiment, the components of the first cleaning solution include an oxidizing agent and a base, the oxidizing agent includes hydrogen peroxide, and the base includes one or both of potassium hydroxide and tetramethylammonium hydroxide.

[0024] In a preferred embodiment, in the first cleaning solution, the weight ratio of the base to hydrogen peroxide is (0.1-1):(0.1-1), and the weight ratio of the base to water is (0.1-1):(5-10).

[0025] In an embodiment, in each cleaning cycle, the cleaning temperature of the oxidizing cleaning is 40-80°C, and the cleaning duration is 120-240s.

[0026] In an embodiment, the percentage concentration of the second cleaning solution is 0.1-30% by volume.

[0027] In an embodiment, in each cleaning cycle, the cleaning temperature of the secondary cleaning is 40-80°C, and the cleaning duration is 10-240s.

[0028] In a preferred embodiment, the solute of the secondary cleaning solution includes one or more of ammonia, potassium hydroxide, sodium hydroxide, and tetramethylammonium hydroxide.

[0029] In an embodiment, the thickness of the insulating pattern layer is 30-70nm.

[0030] In a preferred embodiment, a plurality of notches are formed on the first functional pattern layer, the notches penetrate the first functional pattern layer to expose the silicon substrate of the back contact solar cell substrate; wherein the first functional pattern layer includes a first intrinsic pattern layer, a first doped pattern layer, and the insulating pattern layer which are sequentially stacked along the thickness direction, and the first intrinsic pattern layer is formed on the back surface of the silicon substrate.

[0031] In a specific embodiment, the method further includes:

[0032] providing a silicon substrate;

[0033] forming a passivation layer on the front surface of the silicon substrate;

[0034] sequentially forming an intrinsic material layer, a doped material layer, and an insulating material layer on the back surface of the silicon substrate;

[0035] performing a patterning etching process on the back surface of the silicon substrate to form a plurality of the notches on the back surface of the silicon substrate, and to form the remaining intrinsic material layer, the remaining doped material layer and the remaining insulating material layer into the first intrinsic pattern layer, the first doped pattern layer and the insulating pattern layer.

[0036] In an embodiment, the method further comprises: disposing an anti-reflection layer away from the surface of the silicon substrate on the passivation layer.

[0037] In an embodiment, the method further comprises:

[0038] forming a second functional material layer on the surface of the first functional pattern layer away from the silicon substrate and in the notch, the second functional material layer comprising a second intrinsic material layer and a second doped material layer stacked in sequence along a thickness direction, wherein the material of the first doped pattern layer is selected from one of an N-type doped material and a P-type doped material, and the material of the second doped material layer is selected from the other of the N-type doped material and the P-type doped material;

[0039] performing patterning on the second functional material layer and the first functional pattern layer to form a plurality of electrode openings, each of the electrode openings penetrating the second doped material layer, the second intrinsic material layer of the second functional material layer and the insulating pattern layer of the first functional pattern layer to expose the first doped pattern layer of the first functional pattern layer, and the remaining part of the second functional material layer forming a second functional pattern layer; the electrode openings are arranged alternately with the notches.

[0040] In an embodiment, the method further comprises: forming the remaining second doped material layer and the remaining second intrinsic material layer on the first functional pattern layer between the electrode openings and the notches into a first intrinsic pattern part and a first doped pattern part, respectively, and forming the remaining second doped material layer and the remaining second intrinsic material layer in the notches into a second intrinsic pattern part and a second doped pattern part, respectively.

[0041] In an embodiment, the method further comprises:

[0042] forming a light-transmitting electrode layer on the back contact solar cell substrate formed with the second functional pattern layer;

[0043] performing patterning on the light-transmitting electrode layer to obtain a plurality of light-transmitting electrodes;

[0044] forming a corresponding metal electrode layer on each of the light-transmitting electrodes.

[0045] In an embodiment, the method further comprises:

[0046] forming corresponding light-transmitting electrodes at the electrode opening positions and the notch positions respectively on the back contact solar cell substrate;

[0047] performing patterning on the light-transmitting electrode layer to form first light-transmitting electrodes from the light-transmitting electrodes remaining at the electrode opening positions, wherein the first light-transmitting electrodes are in contact with the first doped pattern layers exposed by the electrode openings; the first light-transmitting electrodes extend out of the electrode openings along the sidewalls of the electrode openings and are respectively overlapped on the surfaces of the first doped pattern portions on both sides of the electrode openings;

[0048] forming second light-transmitting electrodes from the light-transmitting electrodes remaining at the notch positions, wherein the second light-transmitting electrodes are in contact with the second doped pattern portions in the notches; the second light-transmitting electrodes extend out of the notches along the sidewalls of the notches and are respectively overlapped on the surfaces of the first doped pattern portions on both sides of the notches; and the first light-transmitting electrodes and the second light-transmitting electrodes on the same surface of the first doped pattern portions are arranged apart from each other;

[0049] forming first metal electrodes on the first light-transmitting electrodes and forming second metal electrodes on the second light-transmitting electrodes.

[0050] The second aspect of the present application provides a back contact solar cell prepared by the method according to the first aspect of the present application.

[0051] The third aspect of the present application provides a back contact solar cell, comprising a back contact solar cell substrate and an electrode layer arranged on the back of the back contact solar cell substrate; wherein the back contact solar cell substrate comprises:

[0052] a silicon substrate;

[0053] a first functional pattern layer arranged on the back of the silicon substrate; the first functional pattern layer comprises a first intrinsic pattern layer, a first doped pattern layer and an insulating pattern layer arranged in layers; the first intrinsic pattern layer is formed on the back of the silicon substrate;

[0054] a notch penetrating through the first functional pattern layer, the bottom surface of the notch being the back of the silicon substrate;

[0055] a second functional pattern layer comprising a portion of the second functional pattern layer on the first functional pattern layer and a portion of the second functional pattern layer in the notch of the first functional pattern layer; the portion of the second functional pattern layer on the first functional pattern layer comprises a first intrinsic pattern portion and a first doped pattern portion arranged in layers on the surface of the insulating pattern layer; the portion of the second functional pattern layer in the notch of the first functional pattern layer comprises a second intrinsic pattern portion and a second doped pattern portion arranged in layers in the notch;

[0056] electrode openings, the electrode openings penetrating the second functional pattern layer, the portions of the first functional pattern layer on which the second functional pattern layer is located, and the insulating pattern layer, a bottom surface of the electrode openings being a surface of the first doped pattern layer away from the silicon substrate; the electrode openings being alternately arranged with the notches;

[0057] an electrode layer being arranged in the notches and the electrode openings.

[0058] In an embodiment, the light-transmitting electrode includes a first light-transmitting electrode and a second light-transmitting electrode.

[0059] The first light-transmitting electrode is arranged in the electrode openings, and is in contact with the first doped pattern layer at the bottom surface of the electrode openings; the first light-transmitting electrode extends out of the electrode openings along the sidewalls of the electrode openings, and is respectively overlapped on the surfaces of the first doped pattern portions on both sides of the electrode openings.

[0060] The second light-transmitting electrode is arranged in the notches, and is in contact with the second doped pattern portions in the notches; the second light-transmitting electrode extends out of the notches along the sidewalls of the notches, and is respectively overlapped on the surfaces of the first doped pattern portions on both sides of the notches; and the first light-transmitting electrode and the second light-transmitting electrode are arranged separately on the same surface of the first doped pattern portion.

[0061] In an embodiment, the metal electrode includes a first metal electrode and a second metal electrode; the first metal electrode is arranged on the first light-transmitting electrode, and the second metal electrode is arranged on the second light-transmitting electrode.

[0062] In an embodiment, the back contact solar cell further includes an anti-reflection layer arranged on a surface of the passivation layer away from the silicon substrate.

[0063] The application provides a method for preparing a back contact solar cell, which comprises the step of cleaning a back contact solar cell substrate, wherein after an etching process, oil stains are left, and the remaining oil stains and particles attached to the surface of the back contact solar cell substrate can be removed by using an alkaline cleaning solution with oxidizing property. Meanwhile, in the process of oxidizing cleaning, the oxidizing property of the first cleaning solution forms an oxide layer on the surface of the silicon substrate. The oxide layer formed by the oxidizing cleaning is silicon oxide, and the back contact solar cell substrate after the oxidizing cleaning is cleaned again by using a second cleaning solution (alkaline solution), so that the formed oxide layer can be removed, and the second cleaning can further remove the remaining semiconductor particles. Under the action of the first cleaning solution, part of the remaining contaminants are sealed in the oxide layer formed by the oxidizing cleaning. Therefore, prolonging the cleaning time of the first cleaning solution cannot remove the remaining contaminants sealed in the oxide layer formed by the oxidizing cleaning. In the second cleaning, the alkaline solution can open the oxide layer formed in the process of oxidizing cleaning, and expose the remaining contaminants originally sealed in the oxide layer. With the further cleaning, the remaining contaminants originally sealed in the oxide layer can be removed. That is, through multiple cleaning, the purpose of removing stubborn residues and contaminants can be achieved.

[0064] By using the preparation method provided by the application, the organic residues such as oil stains and the remaining semiconductor particles on the surface of the back contact solar cell substrate can be removed without damaging the back contact solar cell substrate, which is beneficial to the subsequent process. After removing the semiconductor particles on the surface of the back contact solar cell substrate, the traps and carrier recombination caused by the defects on the surface of the back contact solar cell substrate due to the semiconductor particles can be eliminated, so that the open circuit voltage of the solar cell can be improved, and the photoelectric conversion efficiency of the prepared back contact solar cell can be improved. In addition, after cleaning the back contact solar cell substrate by using the cleaning method, the parts exposed by the gap of the first functional pattern layer on the silicon substrate can be further passivated, which is beneficial to improving the performance of the back contact solar cell.

[0065] The features and advantages of the application will be described in detail in the following specific embodiments and drawings. The best embodiment or means of the application will be fully described in combination with the drawings, but it is not a limitation on the technical solutions of the application. In addition, the features, elements and components appearing in each of the following text and drawings are multiple, and different symbols or numbers are marked for the convenience of representation, but all represent the same or similar structure or function parts. BRIEF DESCRIPTION OF DRAWINGS

[0066] The application will be further described in combination with the drawings:

[0067] FIG. 1 is a flow chart of one embodiment of a cleaning cycle of the cleaning step in the method for preparing a back contact solar cell provided in the present application;

[0068] FIG. 2 is a flow chart of another embodiment of the cleaning step in the method for preparing a back contact solar cell provided in the present application;

[0069] FIG. 3 is a flow chart of one embodiment of the preparation method provided in the present application;

[0070] FIG. 4 is a structural schematic diagram of one embodiment of a back contact solar cell in the related art;

[0071] FIG. 5 is a structural schematic diagram of one embodiment of a back contact solar cell substrate;

[0072] FIG. 6 is a structural schematic diagram of one embodiment of a solar cell provided in the present application;

[0073] FIG. 7 is a flow chart of one optional embodiment of step S230;

[0074] FIG. 8a is a PL effect diagram of a back contact solar cell substrate after one cleaning cycle in Example 1;

[0075] FIG. 8b is a PL effect diagram of a back contact solar cell substrate after two cleaning cycles in Example 1;

[0076] FIG. 8c is a PL effect diagram of a back contact solar cell substrate after three cleaning cycles in Example 1;

[0077] FIG. 9a is a PL effect diagram of a back contact solar cell substrate after one cleaning cycle in Example 2;

[0078] FIG. 9b is a PL effect diagram of a back contact solar cell substrate after two cleaning cycles in Example 2;

[0079] FIG. 9c is a PL effect diagram of a back contact solar cell substrate after three cleaning cycles in Example 2;

[0080] FIG. 10 is a PL effect diagram of an initial substrate obtained in Preparation Example 2 after cleaning.

[0081] Reference numerals 100: silicon substrate 101: passivation layer 102: first intrinsic pattern layer 103: first doped pattern layer 104: insulating pattern layer 105: anti-reflective layer 110: first functional pattern layer 200: second functional pattern layer 200a: part of the second functional pattern layer on the first functional pattern layer 200b: part of the second functional pattern layer in the notch 202a: first intrinsic pattern part 202b: second intrinsic pattern part 203a: first doped pattern part 203b: second doped pattern part 301a: first light-transmitting electrode 301b: second light-transmitting electrode 302a: first metal electrode 302b: second metal electrode DETAILED DESCRIPTION

[0082] Embodiments of the present application are described below in detail with reference to the accompanying drawings, in which like or similar elements are denoted by like or similar reference numerals throughout the drawings. The embodiments described in the embodiments are intended to explain the present application, and cannot be understood as limiting the present application.

[0083] In the present specification, "one embodiment" or "an embodiment" or "example" or "exemplary" means that a specific feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present disclosure. The appearances of the phrase "in one embodiment" in various places in the specification are not necessarily all referring to the same embodiment.

[0084] It should be noted that the "front surface" referred to in the present application means a surface for receiving sunlight on a back contact solar cell, and the "back surface" referred to in the present application means a surface opposite to the "front surface" of the back contact solar cell.

[0085] As shown in FIG. 5, the back contact solar cell substrate includes a silicon substrate 100 and a first functional pattern layer 110 disposed on the back surface of the silicon substrate 100, wherein the first functional pattern layer 110 includes an insulating pattern layer 104. In one specific embodiment, the insulating pattern layer 104 is made of nitride of silicon or oxynitride of silicon.

[0086] In a first aspect of the present application, a method for preparing a solar cell is provided, as shown in FIG. 3, the method for preparing includes:

[0087] In step S210, a back contact solar cell substrate is provided, wherein the back contact solar cell substrate comprises a silicon substrate 100 and a first functional pattern layer 110 disposed on the back surface of the silicon substrate 100, wherein the first functional pattern layer 110 comprises an insulating pattern layer 104;

[0088] In step S220, the back contact solar cell substrate is cleaned by a cleaning method; as shown in FIG. 1, the cleaning method comprises at least two cleaning periods, and each cleaning period comprises:

[0089] In step S110, the back contact solar cell substrate is cleaned by an oxidizing cleaning method using a first cleaning solution, wherein the first cleaning solution comprises an alkaline cleaning solution with oxidizing property, and is used to remove surface contamination particles of the back contact solar cell substrate;

[0090] In step S120, the back contact solar cell substrate cleaned by the oxidizing cleaning method is cleaned again by a second cleaning solution, wherein the second cleaning solution comprises an alkali solution, and the second cleaning solution is suitable for dissolving silicon oxide;

[0091] In step S230, a second functional pattern layer 200 and an electrode layer are sequentially formed on the back surface of the cleaned back contact solar cell substrate.

[0092] In one embodiment, in order to further maintain the cleanliness of the back contact solar cell substrate, as shown in FIG. 2, the cleaning method further comprises:

[0093] In step S130, the back contact solar cell substrate cleaned by at least one cleaning period is cleaned by an acid cleaning method using a non-oxidizing acid.

[0094] After step S130, the non-oxidizing acid can neutralize the residual alkali solution remaining on the back contact solar cell substrate, and remove metal particles on the back contact solar cell substrate, so as to ensure the cleanliness of the surface of the back contact solar cell substrate.

[0095] In one specific embodiment, the non-oxidizing acid comprises hydrochloric acid; in one preferred embodiment, the concentration of the hydrochloric acid is 1% to 15% by volume.

[0096] In the embodiments of the present application, after the etching process, oil stains remain; the alkaline cleaning solution with oxidizing property can remove the residual oil stains and particles (mostly residual semiconductor material in the first functional pattern layer) attached to the surface of the back contact solar cell substrate due to the oil stains.

[0097] Meanwhile, in the process of the oxidation cleaning, the oxidation of the first cleaning solution not only forms an oxide layer on the surface of the silicon substrate 100, but also protects the first functional pattern layer 110 on the back contact solar cell substrate, especially the insulating pattern layer 104 of the first functional pattern layer 110.

[0098] The oxide layer formed by the oxidation cleaning is mainly silicon oxide. The back contact solar cell substrate after the oxidation cleaning is cleaned again by the second cleaning solution (alkali solution), so that the formed oxide layer can be removed, and the residual semiconductor material particles can be further removed. Since the second cleaning solution is an alkali solution, the damage to the insulating pattern layer 104 in the process of the second cleaning is very small. The thickness of the insulating pattern layer 104 removed each time is about 0.3 nm to 5 nm. Therefore, after multiple cleaning cycles, the integrity of the first functional pattern layer 110 on the back contact solar cell substrate can still be ensured, and the alkali solution can further passivate the part of the silicon substrate 100 exposed through the gap of the first functional pattern layer 110.

[0099] By the cleaning steps in the preparation method provided in the present application, the organic matter such as oil stains and the residual semiconductor particles on the surface of the back contact solar cell substrate can be removed without damaging the back contact solar cell substrate, which is beneficial to the subsequent process. After the semiconductor particles on the surface of the back contact solar cell substrate are removed, the traps and carrier recombination caused by the defects on the surface of the back contact solar cell substrate due to the semiconductor particles can be eliminated, so that the open circuit voltage of the solar cell is improved, and the photoelectric conversion efficiency of the prepared back contact solar cell is improved. In addition, after the back contact solar cell substrate is cleaned by the cleaning method, the part of the silicon substrate 100 exposed through the gap of the first functional pattern layer 110 is further passivated, so that the "trap effect" and "recombination effect" caused by the semiconductor material particles on the surface of the back contact solar cell substrate can be avoided, and the open circuit voltage of the solar cell is improved, and the photoelectric conversion efficiency of the prepared back contact solar cell is improved.

[0100] Before cleaning, there are residual contaminants on the surface of the back contact solar cell substrate. In the cleaning method provided in the embodiments of the present application, first, oxidation cleaning is performed, and under the action of the first cleaning solution, part of the residual contaminants are sealed in the oxide layer formed by the oxidation cleaning. Therefore, prolonging the cleaning time of the first cleaning solution may not be able to remove the residual contaminants sealed in the oxide layer formed by the oxidation cleaning. In the secondary cleaning, the alkali solution can open the oxide layer formed in the oxidation cleaning process, and expose the residual contaminants originally sealed in the oxide layer. With the further performance of the secondary cleaning, the residual contaminants originally sealed in the oxide layer can be removed. That is, by performing multiple cleanings, the purpose of enhancing the removal of stubborn residues and contaminants can be achieved.

[0101] In addition, after at least one cleaning cycle, the back contact solar cell substrate is cleaned by using a non-oxidizing acid, and after neutralizing the residual alkali solution in the previous cleaning cycle, the next cleaning cycle has an oxidizing alkali cleaning solution, which can directly clean the back contact solar cell substrate, without causing excessive hardening, and improving the cleaning efficiency of the first cleaning solution.

[0102] In the embodiments of the present application, the number of cleaning cycles is not specially limited, and can be determined according to actual conditions (for example, the oxidation performance of the first cleaning solution, the specific semiconductor material, the specific type of the second cleaning solution, etc.), as long as the particles remaining on the surface of the back contact solar cell substrate and the oxides formed on the surface of the back contact solar cell substrate can be removed.

[0103] In the embodiments of the present application, the specific components of the first cleaning solution are not specially limited, as long as the oil stains can be removed and the insulating pattern layer on the back contact solar cell substrate is not corroded. As an optional implementation, the components of the first cleaning solution include an oxidizing agent and an alkali.

[0104] Among them, the role of the oxidizing agent is to slightly oxidize the back contact solar cell substrate to protect the insulating layer, and the role of the alkali is to remove the oil stains.

[0105] In the embodiments of the present application, the solvent of the first cleaning solution is not specially limited, as long as it can dissolve the oxidizing agent and the alkali, and will not cause secondary pollution to the back contact solar cell substrate. In a specific implementation, the solvent of the first cleaning solution can be water. That is, the first cleaning solution includes water, an oxidizing agent and an alkali.

[0106] In the embodiments of the present application, the oxidizing agent in the first cleaning solution is not specially limited, as long as it does not corrode the insulating pattern layer of the back contact solar cell substrate, and does not cause excessive damage to the silicon substrate when oxidizing the silicon substrate of the back contact solar cell substrate.

[0107] As an optional embodiment, the oxidizing agent can include hydrogen peroxide, and the base can include one or both of potassium hydroxide and tetramethylammonium hydroxide.

[0108] In a preferred embodiment, the weight ratio of the base to the hydrogen peroxide in the first cleaning solution is (0.1-1):(0.1-1), and the weight ratio of the base to water is (0.1-1):(5-10).

[0109] In an embodiment, the cleaning temperature of the oxidizing cleaning is 40-80°C, and the cleaning time is 120-240 seconds in each cleaning cycle.

[0110] As an optional embodiment, the concentration of the base solution in the second cleaning solution is 0.1-30% by volume.

[0111] In an embodiment, the cleaning temperature of the secondary cleaning is 40-80°C, and the cleaning time is 10-240 seconds in each cleaning cycle.

[0112] In the embodiments of the present application, the type of the base in the secondary cleaning solution is not particularly limited. The base can only dissolve the oxide of silicon and not damage the insulating layer. As an optional embodiment, the solute of the secondary cleaning solution can include one or more of ammonia, potassium hydroxide, sodium hydroxide, and tetramethylammonium hydroxide.

[0113] In the embodiments of the present application, the material of the insulating pattern layer can be the oxide of silicon or the nitride of silicon. When the secondary cleaning solution is used to clean the insulating pattern layer, the thickness removed each time is about 0.5-3 nm. Therefore, the thickness of the insulating pattern layer can be 30-70 nm, so that the thickness of the insulating pattern layer on the back contact solar cell substrate after the cleaning method is completed is still greater than 20 nm, and there is still a sufficient thickness of the insulating pattern layer on the back contact solar cell substrate after the cleaning method is completed.

[0114] In a specific embodiment, the thickness of the insulating pattern layer can be 50 nm.

[0115] As an optional embodiment, the cleaning cycle further includes the following step performed between the step of the oxidizing cleaning and the step of the secondary cleaning:

[0116] The back contact solar cell substrate after the oxidizing cleaning is washed with water.

[0117] The back contact solar cell substrate after the oxidizing cleaning is washed with water, so that the first cleaning solution remaining on the back contact solar cell substrate can be removed.

[0118] As an optional embodiment, the number of cleaning cycles is 2 to 5.

[0119] As an optional embodiment, ultrasonic waves can be provided to assist cleaning during the cleaning cycle, and the first cleaning liquid and / or the second cleaning liquid can be provided in a spraying manner.

[0120] By means of ultrasonic waves and / or spraying, the number of cleaning cycles can be reduced, and the amount of the first cleaning liquid and the second cleaning liquid can be reduced.

[0121] In the embodiments, the structure of the first functional pattern layer 110 on the back contact solar cell substrate is not particularly limited. As an optional embodiment, the back contact solar cell substrate is a substrate of a back contact heterojunction solar cell.

[0122] In a preferred embodiment, as shown in FIG. 5, a plurality of notches are formed on the first functional pattern layer 110, the notches penetrating through the first functional pattern layer 110 to expose the silicon substrate 100 of the back contact solar cell substrate; wherein the first functional pattern layer 110 comprises a first intrinsic pattern layer 102, a first doped pattern layer 103, and an insulating pattern layer 104 which are sequentially stacked along the thickness direction; wherein the first intrinsic pattern layer 102 is formed on the back surface of the silicon substrate 100.

[0123] In the present disclosure, after the first functional pattern layer 110 is formed by the patterning process, the material particles of the first intrinsic pattern layer 102 and the material particles of the first doped pattern layer 103 will be left on the surface of the back contact solar cell substrate together with the oil stains. By using the cleaning method provided in the present application to clean the back contact solar cell substrate, the material particles of the first intrinsic pattern layer 102, the material particles of the first doped pattern layer 103, and the oil stains can be effectively removed, and not only the insulating pattern layer 104 will not be damaged, but also the part of the silicon substrate 100 exposed through the notches of the first functional pattern layer 110 can be further passivated.

[0124] In an embodiment of the present application, the first doped pattern layer 103 can be an N-type doped pattern layer or a P-type doped pattern layer.

[0125] As another optional embodiment, the back contact solar cell substrate can further comprise a passivation layer 101 disposed on the front surface of the silicon substrate 100, and the material of the passivation layer 101 is usually intrinsic hydrogenated amorphous silicon. Therefore, by using the cleaning method provided in the present application, the passivation layer 101 will not be damaged.

[0126] In an embodiment, the method further comprises:

[0127] providing a silicon substrate 100;

[0128] forming a passivation layer 101 on the front surface of the silicon substrate 100;

[0129] forming an intrinsic material layer, a doped material layer and an insulating material layer on the back surface of the silicon substrate 100 in sequence;

[0130] performing a patterned etching process on the back surface of the silicon substrate 100 to form a plurality of notches on the back surface of the silicon substrate 100, and to form the remaining intrinsic material layer, the remaining doped material layer and the remaining insulating material layer into the first intrinsic patterned layer 102, the first doped patterned layer 103 and the insulating patterned layer 104.

[0131] In a specific embodiment, the method further comprises: disposing an anti-reflection layer 105 on the surface of the passivation layer 101 away from the silicon substrate 100. As an optional embodiment, the material of the anti-reflection layer 105 can be silicon nitride.

[0132] In a preferred embodiment, as shown in FIGS. 6-7, the method further comprises:

[0133] In step S231, a second functional material layer is formed on the surface of the first functional patterned layer 110 away from the silicon substrate 100 and in the notches of the first functional patterned layer 110, the second functional material layer comprising a second intrinsic material layer and a second doped material layer disposed in sequence along the thickness direction, wherein the material of the first doped patterned layer is selected from one of an N-type doped material and a P-type doped material, and the material of the second doped material layer is selected from the other of the N-type doped material and the P-type doped material;

[0134] In step S232, the second functional material layer and the first functional patterned layer 110 are patterned to form a plurality of electrode openings, each of the electrode openings penetrating the second doped material layer, the second intrinsic material layer of the second functional material layer and the insulating patterned layer 104 of the first functional patterned layer 110 to expose the first doped patterned layer 103 of the first functional patterned layer, and the remaining part of the second functional material layer forms a second functional patterned layer 200; the electrode openings are arranged alternately with the notches.

[0135] In the embodiments of the present application, step S231 can also be referred to as “re-plating”.

[0136] In a specific embodiment, as shown in FIG. 6, the method further comprises:

[0137] The remaining second doped material layer and the remaining second intrinsic material layer between the electrode opening and the gap and on the first functional pattern layer 110 are formed into a first intrinsic pattern part 202a and a first doped pattern part 203a respectively, and the remaining second doped material layer and the remaining second intrinsic material layer in the gap are formed into a second intrinsic pattern part 202b and a second doped pattern part 203b respectively.

[0138] In one embodiment, as shown in FIG. 6, the second functional pattern layer 200 includes a part 200a on the first functional pattern layer and a part 200b in the gap of the first functional pattern layer. The second doped pattern part 203b is in the gap of the first functional pattern layer. Further, the part 200a on the first functional pattern layer includes a first intrinsic pattern part 202a and a first doped pattern part 203a, and the part 200b in the gap of the first functional pattern layer includes a second intrinsic pattern part 202b and a second doped pattern part 203b.

[0139] The second doped pattern part 203b and the first doped pattern part 203a are both from the second doped material layer, and the first intrinsic pattern part 202a and the second intrinsic pattern part 202b are both from the second intrinsic material layer. That is, after step S232, the second doped material layer is formed into a part including the first doped pattern part 203a and the second doped pattern part 203b. The second intrinsic material layer is formed into a part including the first intrinsic pattern part 202a and the second intrinsic pattern part 202b. In the embodiment, the material of the second intrinsic material layer can be the same as or different from the material of the first intrinsic pattern layer 102, as long as it can perform intrinsic passivation on the silicon substrate.

[0140] It should be noted that the shapes of the first intrinsic pattern layer, the first doped pattern layer, and the insulating pattern layer are consistent and have a gap exposing the silicon substrate. That is, the first intrinsic pattern layer, the first doped pattern layer, and the insulating pattern layer are formed into the first functional pattern layer by lamination.

[0141] As an optional embodiment, the intrinsic material layer, the doped material layer, and the insulating material layer can be formed by chemical vapor deposition (CVD).

[0142] In the embodiment, how to specifically perform step S231 is not specially limited. The second intrinsic material layer and the second doped material layer can be formed by chemical vapor deposition (CVD).

[0143] In the embodiment, how to specifically perform the step of forming the electrode layer is not specially limited.

[0144] In one embodiment, the method further includes:

[0145] The second functional pattern layer 200 forms a light-transmitting electrode layer away from the surface of the silicon substrate 100;

[0146] The light-transmitting electrode layer is patterned to obtain a plurality of light-transmitting electrodes;

[0147] A metal electrode layer is formed.

[0148] As shown in FIG. 6, the plurality of light-transmitting electrodes include first light-transmitting electrodes 301a corresponding to the electrode openings and second light-transmitting electrodes 301b corresponding to the notches.

[0149] In one specific embodiment, as shown in FIG. 6, the method further includes:

[0150] The corresponding light-transmitting electrodes are respectively formed at the electrode opening positions and the notch positions on the back contact solar cell substrate;

[0151] The light-transmitting electrode layer is patterned so that the remaining light-transmitting electrodes at the electrode opening positions form the first light-transmitting electrodes 301a, wherein the first light-transmitting electrodes 301a are arranged in contact with the first doped pattern layer 103 exposed by the electrode openings; the first light-transmitting electrodes 301a extend out of the electrode openings along the sidewalls of the electrode openings and are respectively overlapped on the surfaces of the first doped pattern portions 203a on both sides of the electrode openings;

[0152] The remaining light-transmitting electrodes at the notch positions form the second light-transmitting electrodes 301b, wherein the second light-transmitting electrodes 301b are arranged in contact with the second doped pattern portions 203b in the notches; the second light-transmitting electrodes 301b extend out of the notches along the sidewalls of the notches and are respectively overlapped on the surfaces of the first doped pattern portions 203a on both sides of the notches; and the first light-transmitting electrodes 301a and the second light-transmitting electrodes 301b on the same surface of the first doped pattern portions 203a are arranged apart from each other;

[0153] A first metal electrode 302a is formed on the first light-transmitting electrodes 301a, and a second metal electrode 302b is formed on the second light-transmitting electrodes 301b. In this application, the first light-transmitting electrodes 301a and the second light-transmitting electrodes 301b, which can also be referred to as first transparent conductive layers and second transparent conductive layers, can be conventional materials in the art.

[0154] In one embodiment, the first light-transmitting electrode 301a comprises a first lap joint, a first connecting part and a second lap joint connected in sequence, the first lap joint laps the surface of the first doped pattern part 203a on the side of the electrode opening, the second lap joint laps the surface of the first doped pattern part 203a on the other side of the electrode opening, and the first connecting part is located in the electrode opening and adheres to the part of the first doped pattern layer 103 located in the electrode opening; the second light-transmitting electrode 301b comprises a third lap joint, a second connecting part and a fourth lap joint connected in sequence, the third lap joint laps the surface of the first doped pattern part 203a on the side of the notch, the fourth lap joint laps the surface of the first doped pattern part 203a on the other side of the notch, and the second connecting part is located in the notch and adheres to the second doped pattern part 203b of the second functional pattern layer located in the notch.

[0155] As shown in FIG. 6, the metal electrode layer comprises a plurality of first metal electrodes 302a and a plurality of second metal electrodes 302b, wherein the first metal electrodes 302a are arranged on the part of the first light-transmitting electrode 301a located in the electrode opening, and the second metal electrodes 302b are arranged on the part of the second light-transmitting electrode 301b located in the notch.

[0156] As an optional embodiment, the light-transmitting electrode can be made of a TCO material, and the metal electrode can be made of silver.

[0157] As an optional embodiment, between the step S220 and the step S230, the preparation method can further comprise:

[0158] The cleaned back contact solar cell substrate is subjected to a water washing treatment and / or a drying treatment.

[0159] In the embodiments of the present application, the step of providing a silicon substrate can comprise:

[0160] providing an initial silicon substrate;

[0161] at least texturing the first surface of the initial silicon substrate to obtain the silicon substrate.

[0162] The second aspect of the present application provides a back contact solar cell prepared by the method according to the first aspect of the present application.

[0163] The third aspect of the present application provides a back contact solar cell, as shown in FIG. 6, comprising a back contact solar cell substrate and an electrode layer arranged on the back surface of the back contact solar cell substrate; wherein the back contact solar cell substrate comprises:

[0164] a silicon substrate 100;

[0165] The first functional pattern layer 110 is arranged on the back surface of the silicon substrate 100; the first functional pattern layer 110 comprises a first intrinsic pattern layer 102, a first doped pattern layer 103 and an insulating pattern layer 104 arranged in layers; the first intrinsic pattern layer 102 is formed on the back surface of the silicon substrate 100;

[0166] A gap is formed through the first functional pattern layer 110, and the bottom surface of the gap is the back surface of the silicon substrate 100;

[0167] The second functional pattern layer 200 comprises a portion 200a of the second functional pattern layer on the first functional pattern layer and a portion 200b of the second functional pattern layer in the gap of the first functional pattern layer; the portion 200a of the second functional pattern layer on the first functional pattern layer comprises a first intrinsic pattern part 202a and a first doped pattern part 203a arranged in layers on the surface of the insulating pattern layer 104; the portion 200b of the second functional pattern layer in the gap of the first functional pattern layer comprises a second intrinsic pattern part 202b and a second doped pattern part 203b arranged in layers in the gap; the second doped pattern part 203b and the first doped pattern part 203a are both from the second doped material layer, that is, after the step S232, the second doped material layer is formed to comprise the first doped pattern part 203a and the second doped pattern part 203b;

[0168] An electrode opening is formed through the portion 200a of the second functional pattern layer on the first functional pattern layer and the insulating pattern layer 104, and the bottom surface of the electrode opening is the surface of the first doped pattern layer 103 away from the silicon substrate 100; the electrode opening and the gap are arranged alternately;

[0169] An electrode layer is arranged in the gap and the electrode opening correspondingly.

[0170] The surface of the back contact solar cell substrate obtained in the present application is cleaner, which is beneficial to the subsequent process, and also avoids the "trapping effect" and "recombination effect" caused by "impurity particles" on the surface of the back contact solar cell substrate, thereby improving the open circuit voltage of the solar cell and the photoelectric conversion efficiency of the solar cell prepared.

[0171] In the embodiments of the present application, the insulating pattern layer comprises at least one silicon nitride pattern layer and / or at least one silicon oxide pattern layer. Optionally, the thickness of the insulating pattern layer is between 50 nm and 600 nm.

[0172] In a specific embodiment, the electrode layer comprises:

[0173] A light-transmitting electrode is arranged in the gap and the electrode opening correspondingly; and

[0174] a metal electrode, which is arranged on a light-transmitting electrode arranged in the gap and the electrode opening.

[0175] In one embodiment, as shown in FIG. 6, the light-transmitting electrode includes a first light-transmitting electrode 301a and a second light-transmitting electrode 301b.

[0176] The first light-transmitting electrode 301a is arranged in the electrode opening and is in contact with the first doped pattern layer 103 on the bottom surface of the electrode opening. The first light-transmitting electrode 301a extends out of the electrode opening along the sidewall of the electrode opening and is respectively overlapped on the surface of the first doped pattern part 203a on both sides of the electrode opening.

[0177] The second light-transmitting electrode 301b is arranged in the gap and is in contact with the second doped pattern part 203b in the gap. The second light-transmitting electrode 301b extends out of the gap along the sidewall of the gap and is respectively overlapped on the surface of the first doped pattern part 203a on both sides of the gap. The first light-transmitting electrode 301a and the second light-transmitting electrode 301b on the same surface of the first doped pattern part 203a are arranged separately.

[0178] In one embodiment, the first light-transmitting electrode 301a includes a first overlapping part, a first connecting part and a second overlapping part connected in sequence. The first overlapping part is overlapped on the surface of the first doped pattern part 203a on one side of the electrode opening. The second overlapping part is overlapped on the surface of the first doped pattern part 203a on the other side of the electrode opening. The first connecting part is located in the electrode opening and is attached to the part of the first doped pattern layer 103 in the electrode opening. The second light-transmitting electrode 301b includes a third overlapping part, a second connecting part and a fourth overlapping part connected in sequence. The third overlapping part is overlapped on the surface of the first doped pattern part 203a on one side of the gap. The fourth overlapping part is overlapped on the surface of the first doped pattern part 203a on the other side of the gap. The second connecting part is located in the gap and is attached to the part of the second functional pattern layer in the gap (i.e., the second doped pattern part 203b).

[0179] In this application, the first light-transmitting electrode 301a and the second light-transmitting electrode 301b can also be referred to as the first transparent conductive layer and the second transparent conductive layer.

[0180] In one embodiment, as shown in FIG. 6, the metal electrode includes a first metal electrode 302a and a second metal electrode 302b. The first metal electrode 302a is arranged on the first light-transmitting electrode 301a. The second metal electrode 302b is arranged on the second light-transmitting electrode 301b.

[0181] In one specific implementation, as shown in FIG. 6, the back contact solar cell further comprises an anti-reflection layer 105 disposed on the surface of the passivation layer 101 away from the silicon substrate 100.

[0182] Preparation Example 1

[0183] An initial silicon substrate is provided;

[0184] An initial silicon substrate is provided;

[0185] The front surface of the initial silicon substrate is textured to obtain a silicon substrate;

[0186] A passivation layer and an anti-reflection layer are sequentially prepared on the textured surface (i.e., the front surface) of the silicon substrate;

[0187] An intrinsic material layer, a doped material layer, and an insulating material layer are sequentially prepared on the back surface of the textured surface of the silicon substrate;

[0188] An etching process is performed to form an intrinsic pattern layer, a doped pattern layer, and an insulating pattern layer (the thickness of the insulating pattern layer is 50 nm) to form a first functional pattern layer 110, and finally obtain a back contact solar cell substrate. The specific operations of each step have been described in detail in the foregoing content, and will not be repeated here.

[0189] Preparation Example 2

[0190] An initial silicon substrate is provided;

[0191] An initial silicon substrate is provided;

[0192] The front surface of the initial silicon substrate is textured to obtain a silicon substrate;

[0193] A passivation layer and an anti-reflection layer are sequentially prepared on the textured surface (i.e., the front surface) of the silicon substrate;

[0194] An intrinsic material layer, a doped material layer, and an insulating material layer (the thickness of the insulating material layer is 50 nm) are sequentially prepared on the back surface of the textured surface of the silicon substrate to obtain an initial substrate.

[0195] Embodiment

[0196] Embodiment 1

[0197] A cleaning method of a back contact solar cell substrate, comprising:

[0198] The back contact solar cell substrate prepared by the method in Preparation Example 1 is subjected to 3 cleaning cycles, each of which comprises: performing an oxidation cleaning on the back contact solar cell substrate prepared in Preparation Example 1 by using a first cleaning solution, specifically, in the first cleaning solution, the mass ratio of potassium hydroxide, hydrogen peroxide and water is 1:1:7, the cleaning temperature is 40°C, and the cleaning time is 240s; washing with water to remove the residual first cleaning solution on the back contact solar cell; then cleaning the back contact solar cell substrate by using a second cleaning solution, specifically, the second cleaning solution is a 30% by volume sodium hydroxide solution, the cleaning temperature is 60°C, and the cleaning time is 60s; and then washing with water again to remove the residual sodium hydroxide solution.

[0199] After the 3 cleaning cycles, the back contact solar cell substrate is cleaned by using hydrochloric acid with a concentration of 15% by volume.

[0200] The back contact solar cell substrate cleaned by the hydrochloric acid is washed with water and dried.

[0201] Example 2

[0202] The back contact solar cell substrate prepared in Preparation Example 1 is cleaned by using the cleaning method provided in Example 1, which is different from Example 1 in that:

[0203] The first cleaning solution comprises tetramethylammonium hydroxide, hydrogen peroxide and water, and the mass ratio of tetramethylammonium hydroxide, hydrogen peroxide and water is 1:1:6, the cleaning temperature in each oxidation cleaning step is 60°C, and the cleaning time is 240s;

[0204] The second cleaning solution is a 12% by volume potassium hydroxide solution, the cleaning temperature in each secondary cleaning step is 70°C, and the cleaning time is 200s;

[0205] The back contact solar cell substrate is cleaned by using hydrochloric acid with a concentration of 7% by volume.

[0206] Comparative Example

[0207] The initial substrate obtained in Preparation Example 2 is cleaned by using the following method:

[0208] The initial substrate is subjected to a first cleaning by using an oxidizing agent with a concentration of 8% by volume, the cleaning temperature is 50°C, and the time is 240s;

[0209] The initial substrate subjected to the first cleaning is subjected to a second cleaning by using hydrofluoric acid with a concentration of 55% by volume, the cleaning temperature is 30°C, and the time is 100s.

[0210] Test Example

[0211] The following test example introduces the photoluminescence (PL) mean value to characterize the cleanliness of the cleaning. The basic principle of PL luminescence imaging is to excite the sample surface to emit light, and then capture the imaging of the luminescence with a camera. The local luminescence intensity of the imaging is determined by the carrier density and lifetime of the region. Low carrier lifetime, low doping density of carriers, local defects (forming carrier recombination centers and reducing local carrier lifetime), etc. will cause the PL luminescence to weaken; and film layer residues, unclean cleaning, etc. will cause local defects to form carrier recombination centers, thus aggravating carrier recombination, so that the PL luminescence imaging can be used to characterize whether the cleaning is clean. The higher the PL mean value, the cleaner the surface and the better the passivation performance of the surface of the silicon substrate.

[0212] The PL effect diagram of the unetched conventional semiconductor substrate after passivation (comparative example) is shown in FIG. 10, and the PL mean value after cleaning is 50657. It is observed that the insulating material layer on the initial substrate is damaged.

[0213] The PL mean values of the back contact solar cell substrates after 1 cleaning cycle (the PL effect diagram is shown in FIG. 8a), 2 cleaning cycles (the PL effect diagram is shown in FIG. 8b), and 3 cleaning cycles (the PL effect diagram is shown in FIG. 8c) in Example 1 are shown in Table 1.

[0214] Table 1

[0215] As can be seen from Table 1, compared with the comparative example, the cleaning method provided by the present application can significantly improve the surface cleanliness of the back contact solar cell substrate, and the passivation performance of the surface of the silicon substrate is better.

[0216] The PL mean values of the back contact solar cell substrates after 1 cleaning cycle (the PL effect diagram is shown in FIG. 9a), 2 cleaning cycles (the PL effect diagram is shown in FIG. 9b), and 3 cleaning cycles (the PL effect diagram is shown in FIG. 9c) in Example 2 are shown in Table 2.

[0217] Table 2

[0218] As can be seen from Table 2, compared with the comparative example, the cleaning method provided by the present application can significantly improve the surface cleanliness of the back contact solar cell substrate, and the passivation performance of the surface of the silicon substrate is better.

[0219] It can be known through the above tests that the cleaning method provided in the embodiments of the present application can significantly remove the etching film layer residues after cleaning the back contact solar cell substrate, and achieve an ideal cleaning effect, and even achieve the cleaning degree and passivation degree of the initial substrate before etching the initial substrate.

[0220] Embodiment 3

[0221] This embodiment is used to illustrate that the back contact solar cell substrate cleaned by the above embodiments is prepared into a back contact solar cell, which comprises the following steps:

[0222] A second functional material layer is formed on the surface of the first functional pattern layer 110 away from the silicon substrate 100 and in the gap of the first functional pattern layer 110, and the second functional material layer comprises a second intrinsic material layer and a second doped material layer which are sequentially arranged in the thickness direction, wherein the material of the first doped pattern layer is selected from one of an N-type doped material and a P-type doped material, and the material of the second doped material layer is selected from the other of the N-type doped material and the P-type doped material;

[0223] The second functional material layer and the first functional pattern layer 110 are patterned to form a plurality of electrode openings, each of which penetrates the second doped material layer, the second intrinsic material layer of the second functional material layer, and the insulating pattern layer 104 of the first functional pattern layer 110 to expose the first doped pattern layer 103 of the first functional pattern layer, and the remaining part of the second functional material layer forms a second functional pattern layer 200; the electrode openings and the gaps are arranged alternately; the remaining second doped material layer and the remaining second intrinsic material layer located between the electrode openings and the gaps and on the first functional pattern layer 110 are formed into a first intrinsic pattern part 202a and a first doped pattern part 203a, respectively, and the remaining second doped material layer and the remaining second intrinsic material layer located in the gap are formed into a second intrinsic pattern part 202b and a second doped pattern part 203b, respectively;

[0224] Corresponding light-transmitting electrodes are respectively formed at the electrode opening positions and the gap positions on the back contact solar cell substrate;

[0225] The light-transmitting electrode layer is patterned to form a first light-transmitting electrode 301a from the remaining light-transmitting electrode at the electrode opening position, wherein the first light-transmitting electrode 301a is arranged in contact with the first doped pattern layer 103 exposed by the electrode opening; the first light-transmitting electrode 301a extends out of the electrode opening along the sidewall of the electrode opening and is respectively overlapped on the surface of the first doped pattern part 203a on both sides of the electrode opening;

[0226] The remaining light-transmitting electrode at the notch position is formed into a second light-transmitting electrode 301b, wherein the second light-transmitting electrode 301b is arranged in contact with the second doped pattern part 203b in the notch; the second light-transmitting electrode 301b extends out of the notch along the sidewall of the notch and is overlapped on the surface of the first doped pattern part 203a on both sides of the notch respectively; and the first light-transmitting electrode 301a and the second light-transmitting electrode 301b on the same surface of the first doped pattern part 203a are arranged separately;

[0227] A first metal electrode 302a is formed on the first light-transmitting electrode 301a, and a second metal electrode 302b is formed on the second light-transmitting electrode 301b.

[0228] Embodiment 4

[0229] The embodiment provides a back contact solar cell prepared by the method provided in the application, as shown in FIG. 6, which comprises a back contact solar cell substrate and an electrode layer arranged on the back surface of the back contact solar cell substrate; wherein the back contact solar cell substrate comprises:

[0230] a silicon substrate 100;

[0231] a first functional pattern layer 110 arranged on the back surface of the silicon substrate 100; the first functional pattern layer 110 comprises a first intrinsic pattern layer 102, a first doped pattern layer 103 and an insulating pattern layer 104 arranged in layers; the first intrinsic pattern layer 102 is formed on the back surface of the silicon substrate 100;

[0232] a notch penetrating through the first functional pattern layer 110, wherein the bottom surface of the notch is the back surface of the silicon substrate 100;

[0233] a second functional pattern layer 200, which comprises a part 200a of the second functional pattern layer on the first functional pattern layer and a part 200b of the second functional pattern layer in the notch of the first functional pattern layer; the part 200a of the second functional pattern layer on the first functional pattern layer comprises a first intrinsic pattern part 202a and a first doped pattern part 203a arranged in layers on the surface of the insulating pattern layer 104; the part 200b of the second functional pattern layer in the notch of the first functional pattern layer comprises a second intrinsic pattern part 202b and a second doped pattern part 203b arranged in layers in the notch;

[0234] an electrode opening penetrating through the part 200a of the second functional pattern layer on the first functional pattern layer and the insulating pattern layer 104, wherein the bottom surface of the electrode opening is the surface of the first doped pattern layer 103 away from the silicon substrate 100; the electrode opening and the notch are arranged alternately;

[0235] a light-transmitting electrode is arranged in the gap and the electrode opening, respectively;

[0236] a metal electrode is arranged on the light-transmitting electrode in the gap and the electrode opening, respectively;

[0237] The back contact solar cell comprises a first light-transmitting electrode 301a and a second light-transmitting electrode 301b.

[0238] The first light-transmitting electrode 301a is arranged in the electrode opening and is in contact with the first doped pattern layer 103 on the bottom surface of the electrode opening; the first light-transmitting electrode 301a extends out of the electrode opening along the sidewall of the electrode opening and is overlapped on the surface of the first doped pattern part 203a on both sides of the electrode opening, respectively.

[0239] The second light-transmitting electrode 301b is arranged in the gap and is in contact with the second doped pattern part 203b in the gap; the second light-transmitting electrode 301b extends out of the gap along the sidewall of the gap and is overlapped on the surface of the first doped pattern part 203a on both sides of the gap, respectively; and the first light-transmitting electrode 301a and the second light-transmitting electrode 301b on the same surface of the first doped pattern part 203a are arranged separately.

[0240] The back contact solar cell comprises a first metal electrode 302a and a second metal electrode 302b; the first metal electrode 302a is arranged on the first light-transmitting electrode 301a, and the second metal electrode 302b is arranged on the second light-transmitting electrode 301b.

[0241] The back contact solar cell further comprises an anti-reflection layer 105 arranged on the surface of the passivation layer 101 away from the silicon substrate 100.

[0242] The above is only a specific embodiment of the present application, but the protection scope of the present application is not limited to this. Those skilled in the art should understand that the present application includes but is not limited to the content described in the above specific embodiment and the accompanying drawings. Any modification without deviating from the functional and structural principles of the present application shall be included in the scope of the claims.

Claims

1. A method of fabricating a back contact solar cell, characterized by, The method comprises the following steps: providing a back contact solar cell substrate, wherein the back contact solar cell substrate comprises a silicon substrate (100) and a first functional pattern layer (110) arranged on the back of the silicon substrate (100), and the first functional pattern layer comprises an insulating pattern layer (104); cleaning the back contact solar cell substrate; the cleaning method comprises at least two cleaning cycles, and each cleaning cycle comprises: performing oxidation cleaning on the back contact solar cell substrate by using a first cleaning solution, wherein the first cleaning solution comprises an alkaline cleaning solution with oxidizing property, and is used for removing surface contamination particles of the back contact solar cell substrate; performing secondary cleaning on the back contact solar cell substrate after the oxidation cleaning by using a second cleaning solution, wherein the second cleaning solution comprises an alkali solution, and the alkali solution is suitable for etching oxides of silicon on the surface of the silicon substrate; sequentially forming a second functional pattern layer (200) and an electrode layer on the back of the cleaned back contact solar cell substrate.

2. The method of claim 1, wherein, The method further comprises: performing non-oxidizing acid cleaning on the back contact solar cell substrate obtained after at least one cleaning cycle; Optionally, the non-oxidizing acid comprises hydrochloric acid; preferably, the concentration of the hydrochloric acid is 1% to 15% by volume.

3. The method according to claim 1 or 2, characterized in that, The cleaning cycle further comprises the following step performed between the oxidation cleaning step and the secondary cleaning step: performing water cleaning on the back contact solar cell substrate after the oxidation cleaning; Preferably, the number of cleaning cycles is 2 to 5.

4. The method according to any one of claims 1 to 3, characterized in that, The first cleaning solution comprises an oxidizing agent and an alkali; Optionally, the oxidizing agent comprises hydrogen peroxide; and the alkali comprises one or both of potassium hydroxide and tetramethylammonium hydroxide; Preferably, in the first cleaning solution, the weight ratio of the alkali to hydrogen peroxide is (0.1 to 1):(0.1 to 1), and the weight ratio of the alkali to water is (0.1 to 1):(5 to 10). Optionally, in each cleaning cycle, the oxidation cleaning condition comprises: a cleaning temperature of 40°C to 80°C and a cleaning time of 120s to 240s.

5. The method according to any one of claims 1 to 4, characterized in that, The alkali solution in the second cleaning solution has a concentration of 0.1% to 30% by volume; Optionally, in each cleaning cycle, the secondary cleaning condition comprises: a cleaning temperature of 40°C to 80°C and a cleaning time of 10s to 240s; Preferably, the solute of the alkali solution for the secondary cleaning comprises one or more of ammonia, potassium hydroxide, sodium hydroxide and tetramethylammonium hydroxide.

6. The method according to any one of claims 1 to 5, characterized in that, The thickness of the insulating pattern layer is 30nm to 70nm; Preferably, a plurality of notches are formed on the first functional pattern layer (110), the notches penetrate through the first functional pattern layer (110) to expose the silicon substrate (100) of the back contact solar cell substrate; wherein the first functional pattern layer (110) comprises a first intrinsic pattern layer (102), a first doped pattern layer (103) and the insulating pattern layer (104) arranged in sequence along the thickness direction, and the first intrinsic pattern layer (102) is formed on the back of the silicon substrate (100).

7. The method of claim 6, wherein, The method further comprises: A silicon substrate (100) is provided; A passivation layer (101) is formed on the front surface of the silicon substrate (100); An intrinsic material layer, a doped material layer and an insulating material layer are sequentially formed on the back surface of the silicon substrate (100); A patterned etching process is performed on the back surface of the silicon substrate (100) to form a plurality of notches on the back surface of the silicon substrate (100), and the remaining intrinsic material layer, the remaining doped material layer and the remaining insulating material layer are formed into the first intrinsic pattern layer (102), the first doped pattern layer (103) and the insulating pattern layer (104); Optionally, the method further comprises: disposing an anti-reflection layer (105) on the surface of the passivation layer (101) away from the silicon substrate (100).

8. The method of claim 7, wherein, The method further comprises: A second functional material layer is formed on the surface of the first functional pattern layer (110) away from the silicon substrate (100) and in the notches, the second functional material layer comprising a second intrinsic material layer and a second doped material layer sequentially stacked in the thickness direction, wherein the material of the first doped pattern layer is selected from one of an N-type doped material and a P-type doped material, and the material of the second doped material layer is selected from the other of the N-type doped material and the P-type doped material; The second functional material layer and the first functional pattern layer (110) are patterned to form a plurality of electrode openings, each of the electrode openings penetrating the second doped material layer, the second intrinsic material layer of the second functional material layer and the insulating pattern layer (104) of the first functional pattern layer (110) to expose the first doped pattern layer (103) of the first functional pattern layer, and the remaining part of the second functional material layer forming a second functional pattern layer (200); the electrode openings are alternately arranged with the notches; Preferably, the method further comprises: The remaining second doped material layer and the remaining second intrinsic material layer located between the electrode openings and the notches and on the first functional pattern layer (110) are formed into a first intrinsic pattern part (202a) and a first doped pattern part (203a), respectively, and the remaining second doped material layer and the remaining second intrinsic material layer located in the notches are formed into a second intrinsic pattern part (202b) and a second doped pattern part (203b), respectively.

9. The method of claim 8, wherein, The method further comprises: A light-transmitting electrode layer is formed on the back contact solar cell substrate on which the second functional pattern layer (200) is formed; The light-transmitting electrode layer is patterned to obtain a plurality of light-transmitting electrodes; A corresponding metal electrode layer is formed on the plurality of light-transmitting electrodes.

10. The method of claim 9, wherein, The method further comprises: Corresponding light-transmitting electrodes are respectively formed at the electrode opening positions and the notch positions on the back contact solar cell substrate. the light-transmitting electrode layer is patterned to form a first light-transmitting electrode (301a) remaining at the electrode opening position, wherein the first light-transmitting electrode (301a) is arranged in contact with the first doped pattern layer (103) exposed by the electrode opening; the first light-transmitting electrode (301a) extends out of the electrode opening along the sidewall of the electrode opening and overlaps the surface of the first doped pattern part (203a) on both sides of the electrode opening, respectively; a second light-transmitting electrode (301b) is formed remaining at the notch position, wherein the second light-transmitting electrode (301b) is arranged in contact with the second doped pattern part (203b) in the notch; the second light-transmitting electrode (301b) extends out of the notch along the sidewall of the notch and overlaps the surface of the first doped pattern part (203a) on both sides of the notch, respectively; and the first light-transmitting electrode (301a) and the second light-transmitting electrode (301b) on the same surface of the first doped pattern part (203a) are arranged apart from each other; a first metal electrode (302a) is formed on the first light-transmitting electrode (301a), and a second metal electrode (302b) is formed on the second light-transmitting electrode (301b).

11. The back contact solar cell prepared by the method according to any one of claims 1-10.

12. A back contact solar cell, characterized by The back contact solar cell substrate and the electrode layer arranged on the back surface of the back contact solar cell substrate; The back contact solar cell substrate comprises: a silicon substrate (100); a first functional pattern layer (110) arranged on the back surface of the silicon substrate (100); the first functional pattern layer (110) comprises a first intrinsic pattern layer (102), a first doped pattern layer (103) and an insulating pattern layer (104) arranged in layers; the first intrinsic pattern layer (102) is formed on the back surface of the silicon substrate (100); a notch penetrating through the first functional pattern layer (110), the bottom surface of the notch being the back surface of the silicon substrate (100); a second functional pattern layer (200) comprising a part (200a) of the second functional pattern layer on the first functional pattern layer and a part (200b) of the second functional pattern layer in the notch of the first functional pattern layer; the part (200a) of the second functional pattern layer on the first functional pattern layer comprises a first intrinsic pattern part (202a) and a first doped pattern part (203a) arranged in layers on the surface of the insulating pattern layer (104); the part (200b) of the second functional pattern layer in the notch of the first functional pattern layer comprises a second intrinsic pattern part (202b) and a second doped pattern part (203b) arranged in layers in the notch; an electrode opening penetrating through the part (200a) of the second functional pattern layer on the first functional pattern layer and the insulating pattern layer (104), the bottom surface of the electrode opening being the surface of the first doped pattern layer (103) away from the silicon substrate (100); the electrode opening and the notch are arranged alternately; An electrode layer is correspondingly arranged in the gap and the electrode opening.

13. The back contact solar cell of claim 12, wherein, The electrode layer comprises: A light-transmitting electrode is correspondingly arranged in the gap and the electrode opening; and A metal electrode is arranged on the light-transmitting electrode in the gap and the electrode opening. Preferably, the light-transmitting electrode comprises a first light-transmitting electrode (301a) and a second light-transmitting electrode (301b). The first light-transmitting electrode (301a) is arranged in the electrode opening and is in contact with the first doped pattern layer (103) on the bottom surface of the electrode opening; the first light-transmitting electrode (301a) extends out of the electrode opening along the sidewall of the electrode opening and is respectively overlapped on the surface of the first doped pattern part (203a) on both sides of the electrode opening. The second light-transmitting electrode (301b) is arranged in the gap and is in contact with the second doped pattern part (203b) in the gap; the second light-transmitting electrode (301b) extends out of the gap along the sidewall of the gap and is respectively overlapped on the surface of the first doped pattern part (203a) on both sides of the gap; and the first light-transmitting electrode (301a) and the second light-transmitting electrode (301b) on the surface of the same first doped pattern part (203a) are arranged separately. Optionally, the metal electrode comprises a first metal electrode (302a) and a second metal electrode (302b); the first metal electrode (302a) is arranged on the first light-transmitting electrode (301a), and the second metal electrode (302b) is arranged on the second light-transmitting electrode (301b). Optionally, the back contact solar cell further comprises an anti-reflection layer (105) arranged on the surface of the passivation layer (101) away from the silicon substrate (100).

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