Back contact solar cells and their fabrication methods

Abstract

This invention discloses a back-contact solar cell and its fabrication method. The fabrication method of this invention employs a thick silicon oxide layer for insulation of the N-region and P-region of the back-contact cell, achieving physical insulation and eliminating the need for additional insulation measures at the module end. For passivation of the silicon substrate's front side, a combination of thick alumina and silicon nitride is used. The insulating properties of the thick alumina block hole transport, and the high-density negative charge inherent in the alumina film forms a PN junction on the front side of the silicon substrate to block electrons. The use of the alumina and silicon nitride stack reduces the cost of front-side passivation of the back-contact solar cell while ensuring good optical performance.

Description

Technical Field

[0001] This application relates to the field of photovoltaic technology, and in particular to a back-contact solar cell and its preparation method. Background Technology

[0002] Back contact (BC) solar cell technology is an advanced platform technology that can be combined with existing battery technologies to form a series of battery structures with higher efficiency, such as combining with PERC cells to form ABC cells, combining with TOPCon cells to form TBC cells, combining with HJT cells to form HBC cells, and combining with HPBC, PIBC and other cells to form XBC cells. It also has significant advantages in stacked cells.

[0003] Currently, only a few domestic manufacturers possess complete BC battery production technology, and their module efficiencies are all higher than existing battery technologies, indicating that this technology has unique advantages in the large-scale production of high-efficiency batteries. At present, many manufacturers are increasing their R&D investment in BC battery technology and building up new technology reserves. In existing technologies, the boundary between the N-region and P-region of BC batteries is isolated using techniques such as insulating trenches and non-contact spaces. However, if the width of the insulating trench is too narrow or the N-region and P-region are too close, the risk of short circuits will still increase. In the current N-type back-contact battery front passivation, the passivation scheme using silicon oxide and silicon nitride is slightly insufficient; or the passivation scheme using intrinsic amorphous silicon and N-type amorphous silicon oxide and silicon nitride results in severe parasitic absorption. Summary of the Invention

[0004] Therefore, it is necessary to provide a method for fabricating a back-contact solar cell. The method for fabricating a back-contact solar cell of the present invention does not require additional insulation measures to achieve insulation between the N-region and the P-region, achieving good physical isolation, reducing the cost of front-side passivation of the back-contact cell, while ensuring good optical performance of the module.

[0005] One embodiment of this application provides a method for preparing a back-contact solar cell.

[0006] A method for fabricating a back-contact solar cell includes the following steps:

[0007] A tunneling oxide layer and a polycrystalline silicon layer are fabricated on the back side of a silicon substrate;

[0008] The front side of the silicon substrate is texturized on one side and the first passivation layer is prepared.

[0009] A second passivation layer is prepared on both the front and back sides of the silicon substrate;

[0010] The back side of the silicon substrate is first laser-cut to remove part of the polycrystalline silicon layer and part of the tunneling oxide layer in the preset P region;

[0011] Insulating layers are prepared on the front and back sides of the silicon substrate respectively;

[0012] A second laser molding process is performed on the back side of the silicon substrate to remove part of the insulating layer in the preset P region;

[0013] An intrinsic amorphous silicon layer and a doped layer are sequentially fabricated on the back side of a silicon substrate, wherein the doping type of the doped layer is different from that of the polycrystalline silicon layer.

[0014] A third laser molding process is performed on the back side of the silicon substrate, on the preset N regions that are spaced apart from the preset P regions, to obtain a first groove and a second groove, wherein the first groove extends to the polycrystalline silicon layer and the second groove extends to the silicon substrate;

[0015] Remove the doped layer and the intrinsic amorphous silicon layer in the preset N region, and retain a portion of the insulating layer between the preset P region and the preset N region;

[0016] A transparent conductive film is fabricated on the back side of a silicon substrate, and laser grooving is performed on the transparent conductive film to achieve a separation between a predetermined N-region and a predetermined P-region; and

[0017] Metal electrodes are fabricated in the preset P region and the first groove, respectively.

[0018] In some embodiments, the thickness of the tunneling oxide layer is 1 nm to 2 nm;

[0019] And / or the thickness of the polycrystalline silicon layer is 80nm~200nm.

[0020] In some embodiments, the first passivation layer is an aluminum oxide layer, and the thickness of the first passivation layer is 3nm~5nm.

[0021] In some embodiments, the second passivation layer is a silicon nitride layer, and the thickness of the second passivation layer is 120nm~140nm.

[0022] In some embodiments, the insulating layer is a silicon oxide layer, and the thickness of the insulating layer is not less than 100 nm.

[0023] In some embodiments, the thickness of the intrinsic amorphous silicon layer is 7 nm to 12 nm;

[0024] And / or, the thickness of the doped layer is 10nm~25nm.

[0025] In some embodiments, the width ratio of the preset N region to the width ratio of the preset P region is 3:2 to 3:1.

[0026] In some embodiments, the P element doping concentration of the doped layer is ≥1E20 / cm³. 3 .

[0027] In some embodiments, the polycrystalline silicon layer is made of silicon carbide, wherein the carbon content in the polycrystalline silicon layer gradually decreases from the silicon substrate toward the metal electrode, and the highest carbon concentration in the polycrystalline silicon layer is ≥5E21 / cm³. 3 .

[0028] In some embodiments, the thickness of the transparent conductive film within the preset P region is 80 nm to 120 nm.

[0029] In some embodiments, the material of the transparent conductive film includes one or more of ITO, IMO, IWO, ICO, IXO, AZO, and SnO2.

[0030] In some embodiments, before fabricating the tunneling oxide layer and the polycrystalline silicon layer on the back side of the silicon substrate, the following steps are further included:

[0031] The silicon substrate is cleaned to remove organic matter and metal ions from its surface, followed by the removal of surface damage layers and polishing.

[0032] In some embodiments, after forming a tunneling oxide layer and a polycrystalline silicon layer on the back side of the silicon substrate, and before forming a single-sided texturing layer and a first passivation layer on the front side of the silicon substrate, the following steps are further included:

[0033] The silicon substrate is placed in an annealing furnace and annealed and recrystallized at 850℃~900℃ to improve the crystallinity of the polycrystalline silicon layer.

[0034] In some embodiments, the method for preparing the back-contact solar cell further includes the following steps: performing light injection on the prepared back-contact solar cell and conducting performance testing.

[0035] One embodiment of this application also provides a back-contact solar cell.

[0036] A back-contact solar cell, wherein the back-contact solar cell is prepared by the above-described preparation method.

[0037] Compared with traditional technologies, the fabrication method of the back-contact solar cell in this embodiment has the following advantages:

[0038] (1) The front side of the silicon substrate is passivated with aluminum oxide and silicon nitride to ensure both passivation and optical performance.

[0039] (2) Replacing the indium-containing TCO with SnO2 film in the transparent conductive film layer on the back of the silicon substrate can further reduce production costs.

[0040] (3) Using silicon oxide layer as an insulating layer can effectively prevent short circuits.

[0041] (4) Both the N-region and the P-region use a wide-bandgap transparent conductive film layer, which can reduce the light absorption rate of the transparent conductive film layer to a certain extent and further increase the current. Attached Figure Description

[0042] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application, and those skilled in the art can obtain other drawings based on these drawings without creative effort.

[0043] To gain a more complete understanding of this application and its beneficial effects, the following description will be provided in conjunction with the accompanying drawings. In the following description, the same reference numerals denote the same parts.

[0044] Figure 1 This is a schematic diagram of a method for preparing a back-contact solar cell according to an embodiment of the present invention;

[0045] Figure 2 This is a schematic diagram of a back-contact solar cell structure according to an embodiment of the present invention;

[0046] Figure 3 This is a schematic diagram of step (1) of the preparation method of the back contact solar cell according to Embodiment 1 of the present invention;

[0047] Figure 4 This is a schematic diagram of step (2) of the preparation method of the back contact solar cell described in Embodiment 1 of the present invention;

[0048] Figure 5 This is a schematic diagram of step (4) of the preparation method of the back contact solar cell described in Embodiment 1 of the present invention;

[0049] Figure 6 This is a schematic diagram of step (5) of the preparation method of the back contact solar cell described in Embodiment 1 of the present invention;

[0050] Figure 7 This is a schematic diagram of step (6) of the preparation method of the back contact solar cell described in Embodiment 1 of the present invention;

[0051] Figure 8 This is a schematic diagram of step (7) of the preparation method of the back contact solar cell described in Embodiment 1 of the present invention;

[0052] Figure 9 This is a schematic diagram of step (8) of the preparation method of the back contact solar cell described in Embodiment 1 of the present invention;

[0053] Figure 10 This is a schematic diagram of step (10) of the preparation method of the back contact solar cell according to Embodiment 1 of the present invention;

[0054] Figure 11 This is a schematic diagram of step (11) of the preparation method of the back contact solar cell according to Embodiment 1 of the present invention;

[0055] Figure 12 This is a schematic diagram of step (12) of the preparation method of the back contact solar cell according to Embodiment 1 of the present invention;

[0056] Figure 13 This is a schematic diagram of step (13) of the preparation method of the back contact solar cell described in Embodiment 1 of the present invention;

[0057] Figure 14 This is a schematic diagram of step (14) of the preparation method of the back contact solar cell described in Embodiment 1 of the present invention;

[0058] Figure 15 This is a schematic diagram of step (15) of the preparation method of the back contact solar cell described in Embodiment 1 of the present invention.

[0059] Explanation of reference numerals in the attached figures

[0060] 10. Back contact solar cell; 100. Silicon substrate; 200. Tunneling oxide layer; 300. Polycrystalline silicon layer; 400. First passivation layer; 500. Second passivation layer; 600. Insulating layer; 700. Intrinsic amorphous silicon layer; 800. Doped layer; 900. Transparent conductive film; 1010, 1020. Metal electrode; 101. Preset N-region; 102. Preset P-region; 201. First trench; 202. Second trench. Detailed Implementation

[0061] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of the present invention. However, the present invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0062] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0063] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0064] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0065] In the description of this invention, "several" means one or more, "multiple" means two or more, "greater than," "less than," and "exceeding" are understood to exclude the stated number, while "above," "below," and "within" are understood to include the stated number. The use of "first" and "second" in the description is merely for distinguishing technical features and should not be construed as indicating or implying relative importance, or implicitly indicating the number of indicated technical features, or implicitly indicating the order of the indicated technical features.

[0066] In this invention, unless otherwise stated, the sum of the parts of each component in the composition may be 100 parts by weight. Unless otherwise specified, the percentages (including weight percentages) in this invention are based on the total weight of the composition. Furthermore, "wt%" in this document represents mass percentage, and "at%" represents atomic percentage.

[0067] In this document, unless otherwise stated, the reaction steps may be performed in the order described herein or not. For example, other steps may be included between reaction steps, and the order of reaction steps may be appropriately interchanged. This is something that those skilled in the art can determine based on conventional knowledge and experience. Preferably, the reaction methods described herein are performed sequentially.

[0068] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0069] This application provides a method for fabricating a back-contact solar cell 10 to address the problem that the passivation of the front side of the back-contact solar cell using silicon oxide and silicon nitride is slightly insufficient in the prior art; and that the passivation scheme using intrinsic amorphous silicon, N-type amorphous silicon oxide, and silicon nitride has a serious problem of parasitic absorption. The fabrication method of the back-contact solar cell 10 will be described below with reference to the accompanying drawings.

[0070] The method for fabricating the back-contact solar cell 10 provided in this application embodiment is exemplary; please refer to [link to example]. Figure 1 As shown, Figure 1 This is a schematic diagram illustrating the fabrication method of the back-contact solar cell 10 provided in this application embodiment. The fabrication method of the back-contact solar cell 10 of this application can be used to fabricate back-contact batteries.

[0071] To more clearly illustrate the structure of the back contact solar cell 10, the fabrication method of the back contact solar cell 10 will be described below with reference to the accompanying drawings.

[0072] For example, please refer to Figure 1 As shown, Figure 1 This is a schematic diagram illustrating the fabrication method of the back contact solar cell 10 provided in an embodiment of this application.

[0073] A method for fabricating a back-contact solar cell 10 includes the following steps:

[0074] A tunneling oxide layer 200 and a polycrystalline silicon layer 300 are prepared on the back side of a silicon substrate 100;

[0075] The front side of the silicon substrate 100 is texturized on one side and the first passivation layer 400 is prepared.

[0076] A second passivation layer 500 is prepared on the front and back sides of the silicon substrate 100, respectively;

[0077] The back side of the silicon substrate 100 is first laser-cut to remove part of the polysilicon layer 300 and part of the tunnel oxide layer 200 in the preset P region 102.

[0078] Insulating layers 600 are prepared on the front and back sides of the silicon substrate 100, respectively;

[0079] A second laser molding process is performed on the back side of the silicon substrate 100 to remove part of the insulating layer 600 in the preset P region 102.

[0080] An intrinsic amorphous silicon layer 700 and a doped layer 800 are sequentially fabricated on the back side of a silicon substrate 100. The doping type of the doped layer 800 is different from that of the polycrystalline silicon layer 300.

[0081] A third laser molding is performed on the preset N region 101, which is distributed at intervals with the preset P region 102 on the back side of the silicon substrate 100, to obtain a first groove 201 and a second groove 202, wherein the first groove 201 extends to the polysilicon layer 300 and the second groove 202 extends to the silicon substrate 100.

[0082] Remove the doped layer 800 and the intrinsic amorphous silicon layer 700 from the preset N region 101, and retain a portion of the insulating layer 600 between the preset N region 101 and the preset N region 101.

[0083] A transparent conductive film 900 is fabricated on the back side of a silicon substrate 100, and laser grooving is performed on the transparent conductive film 900 to achieve a separation between the transparent conductive film 900 in a predetermined N-region 101 and a predetermined P-region 102; and

[0084] Metal electrodes 1010 and 1020 are fabricated on the preset P region 102 and the first trench 201, respectively; the structure of the fabricated back contact solar cell 10 is shown in [reference]. Figure 2 As shown, Figure 2 This is a schematic diagram of a back-contact solar cell 10 according to an embodiment of the present invention.

[0085] In some embodiments, the thickness of the tunneling oxide layer 200 is 1 nm to 2 nm;

[0086] The thickness of the polycrystalline silicon layer 300 is 80nm~200nm.

[0087] In some embodiments, the first passivation layer 400 is an aluminum oxide layer, and the thickness of the first passivation layer 400 is 3nm~5nm.

[0088] In some embodiments, the second passivation layer 500 is a silicon nitride layer, and the thickness of the second passivation layer 500 is 120nm~140nm.

[0089] In some embodiments, the insulating layer 600 is a silicon oxide layer, and the thickness of the insulating layer 600 is not less than 100 nm.

[0090] In some embodiments, the thickness of the intrinsic amorphous silicon layer 700 is 7 nm to 12 nm;

[0091] And / or, the thickness of the doped layer 800 is 10nm~25nm.

[0092] In some embodiments, the width ratio of the preset N region 101 to the width ratio of the preset P region 102 is 3:2 to 3:1.

[0093] In some embodiments, the P element doping concentration of the doped layer 800 is ≥1E20 / cm³. 3 .

[0094] In some embodiments, the polycrystalline silicon layer 300 is made of silicon carbide, wherein the carbon content in the polycrystalline silicon layer 300 gradually decreases from the silicon substrate 100 toward the metal electrodes 1010 and 1020, and the highest carbon concentration in the polycrystalline silicon layer 300 is ≥5E21 / cm³. 3 .

[0095] In some embodiments, the thickness of the transparent conductive film 900 within the preset P region 102 is 80nm~120nm.

[0096] In some embodiments, the material of the transparent conductive film 900 includes one or more of ITO, IMO, IWO, ICO, IXO, AZO, and SnO2.

[0097] In some embodiments, before forming the tunneling oxide layer 200 and the polycrystalline silicon layer 300 on the back side of the silicon substrate 100, the following steps are also included:

[0098] The silicon substrate 100 is surface cleaned to remove organic matter and metal ions from its surface, and then the surface damage layer of the silicon substrate 100 is removed and polished.

[0099] In some embodiments, after the tunneling oxide layer 200 and the polysilicon layer 300 are formed on the back side of the silicon substrate 100, and before the front side of the silicon substrate 100 is texturized on one side and the first passivation layer 400 is formed, the following steps are also included:

[0100] The silicon substrate 100 is placed in an annealing furnace and annealed and recrystallized at 850℃~900℃ to improve the crystallinity of the polycrystalline silicon layer 300.

[0101] In some embodiments, the method for preparing the back contact solar cell 10 further includes the following steps: performing light injection on the prepared back contact solar cell 10, and conducting performance testing.

[0102] One embodiment of this application also provides a back-contact solar cell 10.

[0103] A back-contact solar cell 10 is prepared using the above-described preparation method.

[0104] The aforementioned method for fabricating back-contact solar cells employs a thick silicon oxide layer for insulation of the N- and P-regions, achieving physical insulation and eliminating the need for additional insulation measures at the module end. For passivation of the silicon substrate's front side, a combination of thick alumina and silicon nitride is used. The insulating properties of the thick alumina block hole transport, while the high-density negative charge inherent in the alumina film forms a PN junction on the silicon substrate's front side, blocking electrons. The use of the alumina and silicon nitride stack reduces the cost of front-side passivation for back-contact solar cells while ensuring good optical performance.

[0105] Example 1

[0106] This embodiment provides a back-contact solar cell 10.

[0107] The back-contact solar cell 10 of this embodiment is prepared using the following method.

[0108] A method for fabricating a back-contact solar cell 10 includes the following steps:

[0109] (1) The N-type silicon substrate 100 is surface-cleaned to remove organic matter and metal ions from its surface, followed by removal of the surface damage layer and polishing. See [link to relevant documentation]. Figure 3 As shown.

[0110] (2) The cleaned N-type silicon substrate 100 is placed in a PECVD (plasma-enhanced chemical vapor deposition) apparatus to prepare a 2 nm thick tunneling oxide layer 200 and a 200 nm thick N-type silicon carbide layer as a polycrystalline silicon layer 300 on the back side of the silicon substrate 100. The carbon content in the polycrystalline silicon layer 300 gradually decreases from the silicon substrate 100 toward the metal electrodes 1010 and 1020, and the highest carbon concentration in the polycrystalline silicon layer 300 is ≥5E21 / cm³. 3 See also Figure 4 As shown.

[0111] (3) Place the silicon substrate 100 into an annealing furnace and anneal and recrystallize at 850°C to improve the crystallinity of the N-type silicon carbide polycrystalline silicon layer 300.

[0112] (4) The front side of the annealed silicon substrate 100 is texturized on one side, and then the silicon substrate 100 is placed in an ALD (atomic layer deposition) device to prepare a 5nm thick aluminum oxide layer as the first passivation layer 400 on the front side of the silicon substrate 100. See Figure 5 As shown.

[0113] (5) The silicon substrate 100 with the first passivation layer 400 is placed in a tubular PECVD process, and silicon nitride layers with a thickness of 120 nm are formed on the front and back sides of the silicon substrate 100 as the second passivation layer 500. See Figure 6 As shown.

[0114] (6) Perform a first laser molding process on the back side of the silicon substrate 100 to remove part of the N-type silicon carbide polycrystalline silicon layer 300 and part of the tunneling oxide layer 200 in the preset P region 102. See [link to documentation] Figure 7 As shown.

[0115] (7) The intermediate obtained in step (6) is placed in APCVD (atmospheric pressure chemical vapor deposition) at 550°C to prepare silicon oxide layers with a thickness of 100 nm on both the front and back sides of the silicon substrate 100 as insulating layers 600. See Figure 8 As shown.

[0116] (8) Perform a second laser molding process on the back side of the silicon substrate 100 to remove part of the insulating layer 600 in the preset P region 102. See [link to documentation]. Figure 9 As shown.

[0117] (9) Clean the intermediate after laser film opening in step (8) to remove the uneven insulating layer 600 and laser damage layer caused by laser film opening.

[0118] (10) The intermediate obtained in step (9) is placed in low-temperature PECVD (plasma-enhanced chemical vapor deposition) to sequentially prepare an intrinsic amorphous silicon layer 700 with a thickness of 10 nm and a P-type doped microcrystalline silicon carbide layer with a thickness of 10 nm as a doping layer 800 on the back side of the silicon substrate 100. The P element doping concentration of the P-type doped microcrystalline silicon carbide layer is ≥1E20 / cm 3 See also Figure 10 As shown.

[0119] (11) A third laser molding process is performed on the preset N regions 101, which are spaced apart from the preset P regions 102 on the back side of the silicon substrate 100, to obtain one or more first trenches 201 and second trenches 202, wherein the first trenches 201 extend to the polysilicon layer 300 and the second trenches 202 extend to the silicon substrate 100. The width ratio of the preset N regions 101 to the width of the preset P regions 102 is 3:2. See [link to relevant documentation] Figure 11 As shown.

[0120] (12) The P-type doped microcrystalline silicon carbide layer and intrinsic amorphous silicon layer 700 in the preset N region 101 are removed by wet process, leaving a portion of the insulating layer 600 between the preset N region 101 and the preset P region 102. See Figure 12 As shown.

[0121] (13) A transparent conductive film 900 with a thickness of 100 nm was prepared on the back side of a silicon substrate 100 using a PVD apparatus with TCO material. See [link to PVD equipment] Figure 13 As shown.

[0122] (14) Laser grooving is performed on the transparent conductive film 900 to achieve a separation between the preset N region 101 and the preset P region 102, preventing leakage. See also Figure 14 As shown.

[0123] (15) Metal electrodes 1010 and 1020 are fabricated on the preset P region 102 and the first groove 201 respectively using screen printing process, see [reference]. Figure 15 As shown. The structure of the fabricated back-contact solar cell 10 is shown in the figure. Figure 2 As shown, Figure 2 This is a schematic diagram of a back-contact solar cell 10 according to an embodiment of the present invention.

[0124] (16) The prepared back contact solar cell 10 was subjected to light injection and performance testing.

[0125] The method for preparing the back contact solar cell 10 in this embodiment has the following beneficial effects:

[0126] (1) The front side of the silicon substrate 100 is passivated with aluminum oxide and silicon nitride to ensure both passivation and optical performance.

[0127] (2) Using silicon oxide layer as isolation layer can effectively avoid short circuit.

[0128] (3) Both the N-region and the P-region use a wide-bandgap transparent conductive film 900 layer, which can reduce the light absorption rate of the transparent conductive film 900 layer to a certain extent and further increase the current.

[0129] Example 2

[0130] This embodiment provides a back-contact solar cell.

[0131] The back-contact solar cell in this embodiment was prepared using the following method.

[0132] The preparation method of the back contact solar cell in this embodiment is basically the same as that in embodiment 1. The difference is that step (12) in embodiment 2 lacks the step of "removing the P-type doped microcrystalline silicon carbide layer and intrinsic amorphous silicon layer in the preset P region" in step (12) of embodiment 1. In addition, only the first trench is opened in step (11), and steps (12) and (13) are adapted and adjusted.

[0133] A method for fabricating a back-contact solar cell includes the following steps:

[0134] (1) The N-type silicon substrate is cleaned to remove organic matter and metal ions from the surface of the silicon substrate, and then the surface damage layer of the silicon substrate is removed and polished.

[0135] (2) The cleaned N-type silicon substrate is placed in a PECVD apparatus to prepare a 2 nm thick tunneling oxide layer and a 200 nm thick N-type silicon carbide polycrystalline silicon layer on the back side of the silicon substrate. The carbon content in the polycrystalline silicon layer gradually decreases from the silicon substrate toward the metal electrode, and the highest carbon concentration in the polycrystalline silicon layer is ≥5E21 / cm³. 3 .

[0136] (3) Place the silicon substrate in an annealing furnace and anneal and recrystallize at 850°C to improve the crystallization rate of the N-type silicon carbide polycrystalline silicon layer.

[0137] (4) The front side of the annealed silicon substrate is textured on one side, and then the silicon substrate is put into the ALD equipment to prepare a 5nm thick aluminum oxide layer as the first passivation layer on the front side of the silicon substrate.

[0138] (5) Place the silicon substrate with the first passivation layer in a tubular PECVD, and prepare silicon nitride layers with a thickness of 120 nm on the front and back sides of the silicon substrate as the second passivation layers.

[0139] (6) Perform the first laser mold opening on the back side of the silicon substrate to remove part of the N-type silicon carbide polycrystalline silicon layer and part of the tunnel oxide layer in the preset P region.

[0140] (7) The intermediate obtained in step (6) is placed in APCVD and silicon oxide layers with a thickness of 100 nm are prepared on the front and back sides of the silicon substrate at 550 °C as insulating layers.

[0141] (8) Perform a second laser mold opening on the back side of the silicon substrate to remove part of the insulating layer in the preset P area.

[0142] (9) Clean the intermediate after laser film opening in step (8) to remove the uneven insulating layer and laser damage layer caused by laser film opening.

[0143] (10) The intermediate obtained in step (9) is placed in a low-temperature PECVD process to sequentially prepare an intrinsic amorphous silicon layer with a thickness of 10 nm and a P-type doped microcrystalline silicon carbide layer with a thickness of 10 nm on the back side of the silicon substrate. The P element doping concentration of the P-type doped microcrystalline silicon carbide layer is ≥1E20 / cm². 3 .

[0144] (11) A third laser molding is performed on the preset N regions, which are distributed at intervals from the preset P regions on the back side of the silicon substrate, to obtain one or more first grooves, wherein the first grooves extend to the N-type silicon carbide polycrystalline silicon layer. The width ratio of the preset N regions to the width of the preset P regions is 3:2.

[0145] (12) A transparent conductive film with a thickness of 100 nm was prepared on the back side of a silicon substrate using SnO2 material through a PVD device.

[0146] (13) A laser is used to create grooves in the transparent conductive film, the P-type doped microcrystalline silicon carbide layer and the intrinsic amorphous silicon layer in the preset N region, so as to achieve the separation of the transparent conductive film, the P-type doped microcrystalline silicon carbide layer and the intrinsic amorphous silicon layer in the preset N region and the preset P region to prevent leakage.

[0147] (14) Metal electrodes are prepared on the preset P area and the first groove using screen printing process.

[0148] (15) Light injection and performance testing were performed on the prepared back contact solar cells.

[0149] This embodiment 2 lacks the step of "removing the P-type doped microcrystalline silicon carbide layer and intrinsic amorphous silicon layer in the preset P region", which can reduce one wet cleaning step and save some process time, but there will also be some efficiency loss.

[0150] The method for preparing the back-contact solar cell in Example 2 has the following beneficial effects:

[0151] (1) The front side of the silicon substrate is passivated with aluminum oxide and silicon nitride to ensure both passivation and optical performance.

[0152] (2) Replacing the indium-containing TCO with SnO2 film in the transparent conductive film layer on the back of the silicon substrate can further reduce production costs.

[0153] (3) Using a silicon oxide layer as an isolation layer can effectively prevent short circuits.

[0154] (4) Both the N-region and the P-region use a wide-bandgap transparent conductive film layer, which can reduce the light absorption rate of the transparent conductive film layer to a certain extent and further increase the current.

[0155] The performance of the back-contact solar cells prepared in Examples 1 and 2 was tested, and the test results are shown in Table 1.

[0156] Table 1

[0157]

[0158] In summary, the fabrication method of the aforementioned back-contact solar cell 10 employs a thick silicon oxide layer 600 for insulation of the N-region and P-region of the back-contact cell, achieving physical insulation and eliminating the need for additional insulation measures at the module end. For the passivation of the front side of the silicon substrate 100, a combination of thick alumina and silicon nitride is used. The insulating properties of the thick alumina block hole transport, and the high-density negative charge inherent in the alumina film forms a PN junction on the front side of the silicon substrate 100 to block electrons. The use of the alumina and silicon nitride stack reduces the cost of front-side passivation of the back-contact solar cell while ensuring good optical performance.

[0159] In the above embodiments, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions in other embodiments.

[0160] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0161] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A method for fabricating a back-contact solar cell, characterized in that, Includes the following steps: A tunneling oxide layer and a polycrystalline silicon layer are fabricated on the back side of a silicon substrate; The front side of the silicon substrate is texturized on one side and the first passivation layer is prepared. A second passivation layer is prepared on both the front and back sides of the silicon substrate; The back side of the silicon substrate is first laser-cut to remove part of the polycrystalline silicon layer and part of the tunneling oxide layer in the preset P region; Insulating layers are prepared on the front and back sides of the silicon substrate respectively; A second laser molding process is performed on the back side of the silicon substrate to remove part of the insulating layer in the preset P region; An intrinsic amorphous silicon layer and a doped layer are sequentially fabricated on the back side of a silicon substrate, wherein the doping type of the doped layer is different from that of the polycrystalline silicon layer. A third laser molding process is performed on the back side of the silicon substrate, on the preset N regions that are spaced apart from the preset P regions, to obtain a first groove and a second groove, wherein the first groove extends to the polycrystalline silicon layer and the second groove extends to the silicon substrate; Remove the doped layer and the intrinsic amorphous silicon layer in the preset N region, and retain a portion of the insulating layer between the preset P region and the preset N region; A transparent conductive film is prepared on the back side of a silicon substrate, and the transparent conductive film is laser-grooved to achieve a separation between the transparent conductive film in a preset N region and a preset P region. as well as Metal electrodes are fabricated in the preset P region and the first groove, respectively; The insulating layer is a silicon oxide layer with a thickness of not less than 100 nm; the first passivation layer is an aluminum oxide layer; and the second passivation layer is a silicon nitride layer.

2. The method for preparing a back-contact solar cell according to claim 1, characterized in that, The thickness of the tunneling oxide layer is 1 nm to 2 nm; And / or the thickness of the polycrystalline silicon layer is 80nm~200nm.

3. The method for preparing a back-contact solar cell according to claim 1, characterized in that, The thickness of the first passivation layer is 3nm~5nm.

4. The method for preparing a back-contact solar cell according to claim 1, characterized in that, The thickness of the second passivation layer is 120nm~140nm.

5. The method for preparing a back-contact solar cell according to claim 1, characterized in that, The thickness of the intrinsic amorphous silicon layer is 7nm~12nm; And / or, the thickness of the doped layer is 10nm~25nm.

6. The method for preparing a back-contact solar cell according to claim 1, characterized in that, The width ratio of the preset N region to the width of the preset P region is 3:2 to 3:

1.

7. The method for preparing a back-contact solar cell according to claim 1, characterized in that, The P element doping concentration of the doped layer is ≥1E20 / cm³. 3 .

8. The method for preparing a back-contact solar cell according to any one of claims 1 to 7, characterized in that, The polycrystalline silicon layer is made of silicon carbide, wherein the carbon content in the polycrystalline silicon layer gradually decreases from the silicon substrate toward the metal electrode, and the highest carbon concentration in the polycrystalline silicon layer is ≥5E21 / cm³. 3 .

9. The method for preparing a back-contact solar cell according to any one of claims 1 to 7, characterized in that, The thickness of the transparent conductive film within the preset P region is 80nm~120nm.

10. The method for preparing a back-contact solar cell according to any one of claims 1 to 7, characterized in that, The material of the transparent conductive film includes one or more of ITO, IMO, IWO, ICO, IXO, AZO, and SnO2.

11. The method for preparing a back-contact solar cell according to any one of claims 1 to 7, characterized in that, Before fabricating the tunneling oxide layer and the polycrystalline silicon layer on the back side of the silicon substrate, the following steps are also included: The silicon substrate is cleaned to remove organic matter and metal ions from its surface, followed by the removal of surface damage layers and polishing.

12. The method for preparing a back-contact solar cell according to any one of claims 1 to 7, characterized in that, After fabricating the tunneling oxide layer and the polycrystalline silicon layer on the back side of the silicon substrate, and before performing single-sided texturing and the first passivation layer on the front side of the silicon substrate, the following steps are also included: The silicon substrate is placed in an annealing furnace and annealed and recrystallized at 850℃~900℃ to improve the crystallinity of the polycrystalline silicon layer.

13. The method for preparing a back-contact solar cell according to any one of claims 1 to 7, characterized in that, The method for preparing the back-contact solar cell further includes the following steps: performing light injection on the prepared back-contact solar cell and conducting performance testing.

14. A back-contact solar cell, characterized in that, The back-contact solar cell is prepared using the preparation method described in any one of claims 1 to 13.

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